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Why did not you employ electron microscope like you did in the other videos? 0.5 um is optical range, and also it seems to reflect more the shape of the cantilever rather than the shape of the blade, besides the imprinting process makes another unknown error into the result.
Sharpness can also be measured on the opposite axis, dragging the edge as done if cutting a tomato. You never see a chef push a knife through a tomato. Rerun the same test with a sawing action and your results will drastically change. Measure y over x with x being a fixed distance.
For a polished edge like the chisel, including a sideways motion will simply have the effect of making the sharp angle sharper. It's exactly like the trick of bicycling up a hill: compare straight up vs going diagonally from the left side of the road to the right side of the road as you ascend the hill. In the latter case, you covered a larger distance for the same rise, so the hill seemed less steep. IOW, for modern (non-serrated) blades, the sawing action does not change the characteristics and if you want to include a sideways motion while cutting we know how that affects the sharpness number you started with. For a napped edge, it may contain microscopic serrations, which contain cutting edges facing different directions. Here, sawing does not make the blade angle sharper but engages a micro-blade at that angle. Being able to cut through a material using saw teeth is a ripping action, different from sharp cutting. That opens up a whole new level of complexity in how to measure and quantify. But, it won't split a hair that way. Note that kitchen knives are purposefully not very sharp, compared to a woodworking chisel. By only using an 800 grit to finish, it leaves a toothy finish on the soft metal at that scale. This grabs the tomato skin when you move across it, and optimizes the knife for cutting foods, in general.
@@JohnDlugosz if I understood your logic in the video, you stated that the obsidian had broken. Therefore it couldn’t be nearly as sharp as the metal. However, even the sharpest metal blade is at best several molecules wide, and the obsidian can be a single molecule wide. Therefore it is fragile. I was simply proposing that you reduce the amount of pressure at any given point of contact by moving across an angle, thereby allowing a greater cutting action at a lower force, preventing the fragile blade from breaking.
Pretty sure a sawing motion would be make the data too inconsistent. Unless you have a very precise robot arm that can replicate the exact motion and apply the same amount of pressure in each test run.
@@tedwintheslyfox9382 uhhh an Arduino, a stepper motor and a small gear setup would suffice, so many rotations over so many thou an inch over x time, what kind of engineer are you?
@@DurokSubaka If you could grind a straight flat edge, that would be the case. But the natural napped edge is like a rugged coastline. Moving sideways will simply engage a different micro-edge that's facing that direction, and buckle and smash it.
But more seriously, applications for obsidian are typically scalpel tools. So it means that instead of a push stroke, it's a gliding stroke across a surface (slicing). Your setup measured sharpness of something pushing; would gliding change the parameters of the problem of sharpness?
it also fails to address obsidians self sharpening via edge fracture. It's not a flaw, but a feature of obsidian as opposed to metal, where instead of becoming dull, it becomes serrated with new sharp facets
Came here to make this exact same comment. I'm sure the obsidian would *cut* hair with a slicing stroke. Splitting hair with a push stroke is a different question.
Would be interesting to be able to capture images that show how serrated it is, as well as be able to compare it to the granular structure of flint (chert and chalcedony).
Beyond the issue of pushing vs dragging, you may also not be producing the obsidian blades the right way: they weren't simply knapped. I do stuff with Mesoamerica (Aztec, Maya, etc) history and archeology, where obsidian was widely used for tools and weapons. I'm more informed on things like Architecture or aqueduct systems then obsidian production; but the way they did it is the prismatic blade method, which isn't simply striking off sharp shards off a starting stone, but is an actual systematic process to work a "core" piece down to produce single even blades with an insanely fine edge. This wasn't a static practice either, there were innovations in obsidian working and prismatic blade production with how the core is struck even only a few centuries prior to Spanish contact in the postclassic period, by which point the region has already been heavily urbanized with city-states and empires for thousands of years and already had a robust obsidian industry. Those innovations in blade production may have actually been what allowed Macuahuitl to pop up in the form the Aztec used them, since it could produce consistently evenly sized and shaped blades, wheras before that the types of weapons used in Mesoamerican warfare didn't tend to have evenly lined edges like that. I can't really go in more depth on this, as I said, obsidian production isn't one of the Mesoamerican topics i'm super informed on (ask me about how cities were laid out or how Aztec political systems work and then I can give you 12 paragraphs!) but yeah, it may be worth looking into prismatic blade production worked.
Their practices were focused on making the edge more durable, not sharper. The sharpest edge of obsidian (that "one molecule thickness" edge), or any knappable material for that matter, is from the flakes that appear paper thin when removed. Obviously a paper thin edge is all but useless for cutting due to how fragile it is, so instead a compromise is used to increase the edge thickness and supporting material to a point where it can handle impacts and repeated cutting without it being a one and done affair. It's a difficult process but most anyone can pick it up with enough time and materials and patience. Knapping your own tools and points is a great way to keep that tradition alive so the knowledge is never forgotten.
@@tylermestek4790 I mean, there's some truth to it, but it's a little misleading: The Uto-Aztecan language family, which Nahuatl (The Aztec language) is a part of, does originate in the Southwestern US. But that being the origin point for the broader language family doesn't mean that the various Nahua groups were hanging out in the SW us directly before they migrated into Central Mexico and became Aztec civilization: Uto-Aztecan languages spread gradually and Nahuatl came about much earlier then those migrations. While we don't know for sure, most researchers and most of the evidence suggests that the Nahuas were in the Bajio region of Northwestern Mexico (So Nayarit Jalisco, etc) when they started to migrate into Central Mexico. The movement of people/languages from the SW US to the Bajio area would have happened centuries or thousands of years before that. But to be honest the development of Nahuatl is not one of the topics I am most well read on, so I can't give many specifics other then what I just said and even then some of that is debated. But no researchers think that the Nahuas travelled directly from the Southwest to Central Mexico: That's not one of the valid competing intepretations, what is is where else in Northern Mexico the Nahuas would have been, how much earlier the spread from the SW to northern mexico was, or if Nahua migrations from Northern Mexico to Central Mexico may have predated the 13th century AD migirations that Nahuatl language accounts assert they happened in. That being said, there is evidence of trade between Maya states and the Southwest US, where Maya merchants brought Macaws, rubber balls, etc up to trade and you can see macaw skeletons, rubber balls, and some ballcourts at Oasisamerican (Pueblo, Hohokam, Salado, etc) sites in the Southwest. It used to be thought that the Mesoamericans were trading those things for turquoise, but recent research shows all/most turquoise used in Mesoamerican art was sourced locally inside Mesoamerica.
@@Skinflaps_Meatslapper There is no point in trying to make obsidian flakes reusable or durable, the qualities that give it the super sharp flakes is the same qualities that make it brittle. Even early humans would carry multiple stones to have access to fresh flakes and constantly need to re-knap their knives. It's just a quality of the rock so it's pretty pointless to make them more durable for a sharpness test.
@@themodernninja8074 Kind of the point I was trying to make. Can you produce an edge with obsidian that's even sharper? Probably so. But there's always a tradeoff, even with steel, between sharpness and durability. The problem with obsidian is that you'll never get to use that full sharpness on anything because it'll flake off the first time you try to cut with it, leaving behind a less acute and duller edge before you're even done with the first cut. That's why the flintknappers of the past were more focused on making a less acute and duller edge that had more durability instead. A knife or point would be useless to them if it was damaged on the first cut and needed to be sharpened again. The obsidian tools they made would hold their edge remarkably well for how brittle the material is, but they still needed to be dressed and resharpened often. Based on evidence and micro flakes at butcher sites, archaeologists believe that they dressed their cutting tools a few times in the process of butchering larger animals such as a bison until they became too dull to use, and then switched to another when they could no longer expediently dress the edge. Later on at camp or whenever they had the time, they'd re-profile the entire edge or repurpose it for something else. They certainly didn't last a long time with normal use and they went through a LOT of them, and that's a big part of why you can find so many of their tools in abundance all over North America. It's a big part of why natives in the West happily abandoned their flint tools when steel knives became available to them via traders and whatnot. They were intimately familiar with flintknapping and knew the limitations of stone tools. The primary reason why they continued to knap was simply to preserve their knowledge and way of life.
As someone who works with obsidian, it is extremely sharp. If cut with a piece of it, it only starts bleeding a few seconds after the initial cut. But I still continue to make arrowheads out of it.
I asked an eye surgeon if he used obsidian blades. He said no they use silicon blades. Diamond blades are available but not used. When the techs sterilize them after surgery they chip them and they are then useless and are discarded
Obsidian *can* achieve a sharper edge, but doing so with any sort of consistency, or more importantly durability to handling and use, is another story.
Debatable. There are jigs and cbn/diamond plates with as low grit as you want, and you can get a steel edge far superior and sharper than glass + tougher.
Brittleness is a highly-prized aspect of obsidian. Prey knock out the shafts soon after they are hit. You WANT the shaft to break, and the projectile point too. If it falls out - wounds close, blood clots. Prey runs miles before being lost. But how far is it going to go with broken pieces of glass working its way deeper towards/in internal organs with every step? Not far. Easily made, easily replaced. Obsidian tools were made to break - and that was great!
Hey, plastic surgeon here. Obsidian scalpels are a real thing. Yes, they are sharper than any other steel edge. The obsidian scalpels are very difficult to find, but I use them on occasion. The obsidian blades are ground, and polished, during manufacturing. How? I don’t know. But they are all uniform in size, thickness, and cut through any tissue with almost zero resistance. Obsidian scalpels are actually scary to use. And that is coming from a surgeon. If you want some, let me know. Happy to send some your way.
Crabtree made obsidian scalpels that were used for his open-heart surgery. The trouble in these tests are multiple. As the narrator pointed out initially, the obsidian is brittle. The second error is more subtle. The "sharpness" test as employed here is simply an attempt to push the edge through the wire. That is fine for any material edge that is arguably as tough (not brittle) as the wire, but plainly isn't going to work if the edge to be tested is brittle and crushes. Also, when used as "recommended," most knives are not simply employed like a wedge. They are drawn or pushed at an angle to the surface being cut. The effective angle of the cutting edge is less than the edge angle measured perpendicular to the edge. Last, the ultimate fineness of an edge is limited by the grain structure of the material. The coarser the grain, the duller the maximum possible sharpness. Obsidian has no grain structure, nor does any other glass. This why, for extremely delicate surgeries many surgeons employ scalpels edged with glass or diamond. However, those same surgeons would not trouble with obsidian in a wood working context.
It's also important to note that the roughness of two tissues when stitched back together increases the efficiency of their ability to seal and heal. So even if we came up with some sort of super material that sliced through tissues literally perfectly, splitting molecules apart or whatever, we wouldn't want to use it on anything we intended to put back together.
@@Marcara081 Roughness would coorrelate to increased trauma to the tissues, which enhances physiological response I think. Evolutionarily, nearly all trauma a body responded to would involve more damage to the tissues at the site, whether it's a scraped, or some sort of puncture like a bite. A cut from a really sharp blade, regardless of material, will separate many cells where a comparable scale injury from a rougher material will rupture cell walls. That releases chemical signals to the surround tissues. It's why cuts from glass bleed so profusely.
@@theeddorian Tears in tissues heal faster and with less complications than cuts, sort of like breaking a popsicle stick in half and then shoving the jagged break back together, rather than cutting it in half with a saw. A jagged break causes the material to interlace with itself and provides much more surface area to join together, just like a tear in tissue will interlace back with itself and heal faster. The medical community doesn't actually agree that finer cuts result in better healing these days, but they did hold that opinion about 50-60 years ago. Precision cuts are only necessary today for minimally invasive surgery and a sharper blade is required, however, it's not the incision itself that benefits from a sharper blade, rather it's from the smaller incision of minimally invasive surgery that allows it to heal better. If you can get away with a 2mm incision rather than a 2cm incision, there will be less to heal...but your blade has to be up to the task of making a precise 2mm incision.
@@Skinflaps_Meatslapper As someone who knaps obsidian, and who works wood, and who sharpens tools and knives by hand, my experience is contrary to that. Low trauma cut from really sharp steel, or glass edges, closes quickly when bandaged properly. Such a cut also heals cleanly and with less scar tissue. Trauma from tears, scrapes, and rips ceases bleeding more quickly. Usually, since the cut from a sharp edge has less surface area, less tissue surface is involved in healing. I asked an ER doc about that years ago, when I notice that some scars I've had since I was three or four are still obvious, while the scars of serious cuts from chipping stone and accidentally bumping the edge of a freshly sharpened knife were completely invisible.
As a bit of a self-appointed expert in sharpness (I'm a bit of a straight razor and honing nerd) there is a very interesting love triangle regarding sharpness. First is the thinness of the edge of course, second is the brittleness of it as you mentioned, but there is also the edge ANGLE that is critical. Basically the 'game' is to get a sharp edge that isn't too brittle by increasing the edge angle. For example, for straight razors, a 'too sharp' razor will 'fold' (or break, if the allow is particularly brittle) it's edge very quickly so is useless -- a 'too blunt' edge will mostly pull hair which makes the shape very uncomfortable. With straight razors, an edge that is too thin can be 'bevelled' by placing table (like, electrical tape) on the back of the blade and redo the edge, to increase the cutting edge angle.
Multi angle bevels are fantastic. Particularly if you work your initial bevel to a fine edge and then just barely work the secondary bevel down, to the point that it's microscopic. You get a larger angle on the edge so it's more durable, but at the same time you reduce the contact area of the bevel on the object you're cutting...instead of the entire bevel sliding across the cut material, it's generally only that micro bevel that's seeing any friction so it cuts with less resistance. I work mostly with knives, so my bevel angles are far greater than a straight razor, but I can get close to that level of sharpness stropping with kangaroo leather and 1um diamond paste.
I have gotten a score of 100 with obsidian when it is knapped skillfully into a blade. The shape matters a lot and you need a skilled knapper to produce them.
It would be interesting to see some experiments of stonemasonry chisels of different materials and edge geometries and how the "cutting" action actually happens.
I'm with you on wanting to see other cutting tools checked this way, ie more methods than just bess testers. The microscope view of the cut happening is very cool. As far as the masonry chisels go, I think that would be interesting to see, but I do not believe it is "cutting" in the sense we tend to think of. I don't use hand chisels at work, but when we drill into concretes and natural rocks (metamorphic and igneous primarily, I think), we use either rotary hammers, which take a carbide chisel point embedded in a normal looking drill bit. That carbide chisel is decidedly *not* sharp normally, and uses the power tool to strike the stone, imparting around 10 lb/ft per impact over the very small chisel area, around 3000 times per minute, and then the rotary action is just clearing the fractured chips up the flutes and out of the hole; alternately, we use diamond hole saws/core drills to abrade away the rock in a fine dust (this actually need active cooling with water, unlike the hammering process). The caveat to that is there are specialty concrete bits designed to cut through rebar in reinforced concrete, and these have a very different carbide striking edge that is also needing to cut iron in this application, and those do tend to be sharper, and have a much tighter radius point at the intersection of the (usually) quad point chisel. My guess for handheld masonry chisels is they operate the same as the rotary hammer method, albeit much slower, with much higher energy imparted per blow, and the edge is being used to concentrate where you are causing the fracture, and the vector of the force, giving a significant level of control compared to a rotary or demolition hammer.
'and how the "cutting" action actually happens.' Having split some pavers and granite rocks by hand for the patio, I can tell you this easily. Doesn't matter how sharp or hard you make the chisel point, it's quickly going to round over and make a narrow but relatively blunt edge. You're hammering the edge against stone, it won't stay sharp. The cutting action is really peaking a large amount of force into that still relatively narrow edge, and locally creating small fractures and some grinding. Eventually you send fractures enough through it that it splits entirely. Go watch videos of splitting stone by hand and it's all basically a fracturing process, not really 'cutting'. Then there are softer stones like marble etc, when carving that you're still setting the chisel at a shallow angle and grinding and fracturing it off. And tool and saw cutting stone is much more related to narrow grinding. Only very soft stone types with a hard sharp edge might do something more like actually cutting the stone apart. A sharper chisel will cut your stone a bit better and faster at first, but it's more about concentrating the fractures better into a narrower space than that it's really 'cutting' the stone better. Sharpen up a masonry chisel and try some, it is very interesting to do. But you'll quickly stop thinking of it as cutting like a knife, and much more like fracturing/grinding under that chisel edge.
Yes this is so. I did the stone masonry course at Bath, and it's what you are told pretty much. A ''hard'' stone is characterised as one that fractures, the chisel edge is controlling the angle of attack and force, producing a fracture that deepens at that angle , and then as the force can't go right through (unless perpendicular) immediately ''spoons'' back up to the surface...your chip. A ''soft ''stone appears to cut, but it is really a micro-crumbling in front of the edge. Cutting non-brittle material is completely different ! And that's where slicing comes in, as the material can be used against itself. I bet the obsidian would win. @@ModelLights
This is stunningly fascinating presentation, regardless of the subject matter. This is exactly what Tim Berners-Lee had in mind when he legged it down the patent office.
Hardened tool steel, if done right, can be both harder and tougher (less brittle) then minerals of silicone dioxide. Flint actually has a granular structure (ranging from microcrystaline to cyrptopcrystaline, as formed from diatoms), which is why it's assumed to be less sharp than obsidian.
@@SkywardSwag I don't know if you're talking about blades or AFM probes, but I just thought of something related to this that may or may not make sense. The reason silicon dioxide is used for AFM, and not tool steel, is because the tip is vibrated at a VERY high frequency. And vibrations in a material can induce harmonics, which can actually heat it up. Tool steel, relatively speaking, is not thermally stable - its thermal expansion coefficient is a bit over 10^-5/K. Silicon, on the other hand, has a coefficient of 5*10^-7/K - that's twenty times smaller than that of tool steel. When you're measuring on the level of angstroms and your probe tip is a nanometer in two in diameter, a millimeter long probe assembly can expand a whole nanometer when exposed to just a fraction of a degree of change in temperature if it is steel. But if it is made of silicon dioxide, that thermal expansion can be limited to under an angstrom. This is also the reason why obsidian works great as a slicing tool, but not as a cutting tool - and why tool steel, even if it keeps its sharpness, will eventually roll the edge on an atomic level - simple contact with the skin would make the edge heat up and expand, and when it contracts, the edge radius will change.
You explain everything with such care. You manage to explain even rather complicated measurement methods such as atomic force microscopy. Take pride in that, loved the video! Oh, and the visuals are also gorgeous, you have a way with cinematography.
8:32 I think because the pressing of the blade was done by hand instead of a true, constant 90 degree downward angle, which made the impression in the lead inaccurate and misshapen. A slight pull of the blade towards the camera; a tilt, has occurred, which pushed the lead cross-section to the left, warping it.
Indeed, it would be interesting to see how well the obsidian cuts a softer material, like planing a piece of wood, or slicing a bit of some kind of flesh...it might well be that planing a piece of pine, measuring the thinnest slice, as is done in Japanese planing contests, might yield an interesting result...
Simply knapping a piece of flint will usually not result in a razor sharp edge. However, due to the structure of obsidian crystals, and the properties of obsidian itself, it can effectively be sharpened to a (near) mono-molecular edge. Common uses for obsidian are surgical tools used on soft tissue, such as scalpels. Hardness, toughness and sharpness are all independent from each other, as is the capacity for one object to hold any one of these properties. What i'm saying is that your test method for sharpness isn't a test method for sharpness. It's a test method for all three. Crystalline structures are WAY too fragile to be subjected to these kinds of localized static pressures, so even though it can be much sharper, it will not ever come out on top of that test. Therefor: _Your test method is inadequate._
Looking at sharpening from grinding wheels etc, but read a comment the other day from someone who use to make obsidian blades for eye surgeons back in the 70's and probably into the early 80's. Said it was very expensive but it was what they used, so you can bet it was the sharpest thing that was reasonably practical even though expensive. Said it largely got phased out by lasers.
Pro cutter here. I earned my chops through 8 years of a commercial kitchen with a chef's knife and 4 years in an Aikido dojo where you use cutting techniques while unarmed.(think of how a river can slowly cut through a mountain or how you could, "cut," through a wooden table with your open palms, using lots of time and sandpaper. Hardness alone can, "cut," but a straight(what I'm going to call focused) edge will magnify the cutting effect at the cost of damage to the edge. I would argue that a square blade that is incredibly hard with a really clean edge can do incredible levels of cutting, while reducing the damage to itself. Heck you can probably even cut with an obtuse edge if your blade is hard enough. There is also a bit of a thing with proper technique. Drawing an edge creates a slice and a slice will greatly increase cutting power over a chop. In many ways using a chisel is also a type of slice, with the greatest cutting happening during the sliding of the chisel and not at the start or and of the gouging stroke.
Great video, very interesting. My only quibble is the practical difference between chopping and slicing. A very thin but weak edge is capable of slicing but not of chopping - anyone who's had a paper cut will bear this out. The obsidian would work quite well if used with a gentle slicing action. I imagine that people using flint and obsidian tools soon discovered this. However sharp, a broadsword worked mainly by smashing bones, not cutting flesh. By way of contrast, a Japanese samurai's sword was a slicing weapon. The extreme hardness of an obsidian edge makes it completely unsuited to chopping, but I'd be interested to see how it performed as a scalpel.
Seemed like an insightful comment to me, but no up votes besides mine? I thought the idea of a slicing test was a good one. I was trying to think of a test where greater sharpness of the obsidian could be demonstrated by cutting something. Your idea seems like a good way of accomplishing that.
No up votes because it's nonsense. A broadsword cuts just as well as a katana, absolute nonsense to call it a smashing weapon and a katana a slicing weapon Katanas should not even be mentioned in this context
@@Tom--Ace I saw the comment more about thinking of a way that a super sharp but super brittle cutting blade might demonstrate cutting superiority in some kinds of situations and that a slicing situation might be one of those situations. I'm not familiar with sword issues. In my ignorance, the sword analogy seemed reasonable to me. Thanks to Tom-Ace's comment I watched the video again and read @EleanorPeterson's comment again. One idea of a situation where the obsidian might be better would be at cutting through soft material. My thought is that if instead of wire the sharpness tester used a thin nylon line the obsidian would cut through it with less force than any metal cutter.
The "point" of obsidian - weaponry. 1) Sharpness but also 2) Brittleness - the 2 most desirable features. (Which explains why copper tools were developed in N America, but didn't catch on.) Obsidian spear/arrow heads are weapons of hunting/war. In an age before beasts of burden, (all on foot! even packing out 200 lbs of meat per person!) you WANT the projectile point to do 2 things, which bring the game down faster. (You don't want it running miles away, into bogs/cliffs/inaccessible areas or found so late the meat spoils.) 1) Penetrate deep; which sharpness allows. -For maximum organ damage/ wound enlargement. (As the prey runs, each step shuffles the rock/glass pieces inside like a tumbler. Cuts more tissue/enlarging wound, severing vessels/arteries.) 2) Breaking in the wound - ensures the cutting edge stays in the prey to continue the damage. -The shaft is like a big stick, it WILL get knocked out due to the prey writhing/rolling/banging it on trees. You want a BREAK. -Non-breaking projectiles that don't penetrate far (less sharp,) can simply fall out with prey movement. The wound can close, blood can clot. Prey can flee to Timbuktu before death. Did they really want projectiles to break? Yes. Trade with others. Get your skilled knappers to tap a few times - boom, replaced. Remember - obsidian tools are "art" to us modern folks. To the ancients - disposable, replaceable, common tools. Meant for USE. "Oh it's so pretty I kinda hope it stays intact and falls out - so we lose our kill we've tracked for 9 days across a glacier and our family is at risk of starving" - said no ancient ever. :) They'd look at copper tools. Less sharp. Pain in the *** to mine/smelt/craft. Soft. Really soft, yet, bendy, not brittle. Falls out of game into grass - oh who cares if we even find it? Let's go back to stone/glass!
Presumably the action of "slicing cut" (dragging the entire sharp surface on object) instead of "wedge cut" (forcing one sharp surface down), kinda help the brittle edge from breaking.
thank god. after years of knowing that obsidian makes the sharpest edges I can't believe I finally see a good video covering the topic. this had me intrigued for the longest time.
Thank you for this insightful video . I learned that for a push cutting action, steel razor are much better suited for this. It flexible nature allows the razors edge to withstand some buckling caused by the force needed to puncturr or slip open the material. This force intuitivly is the peak force of the cutting action because creating a cut or crack in the material surface will cause stress will concentrate in the material. Theerefore the blade will have an easier time pushing wedging apart the material once this crack is made . And it made me think about why the obsidian preformed the way it did. Its clear the edge if the obsidian blade was too thin to with stand the the force need to "puncture". It seems puttin a very small amount of normal compression stress on the on an obsidian edge that thin causes it the buckle, and therefore crumble because of its extreme brittleness. I agree, a slicing motion instead of a pushing motion a better way to test the obsidian. . Which makes sense. You ideally you only want to put shear force against the blade. With an edge that thin, the face it is just a jew atoms in width. That an incredibly small area so the shear stress would be so minimal preserving the sharpness of the blade. Any small amount compression stress will cause the blade to want to buckle abd there for crumble.
i think one of the 'applications' you're talking about is Slicing. slicing being much different than just pushing. The obsidian anecdote comes up mostly in context of cutting human flesh. (historically violently, modernly medically) and from what i remember, it's that obsidian (lacks application in medicine because of the tendency to shatter, but maybe not if our bodies can deal with it) maintains edge hardness longer, and maintains slicing sharpness longer (due to breaking and new edges still being sharp). and also that obsidian is sharp enough to slice cells rather than tearing them. i don't know how much of that is actually true, but i think it's worth consideration.
As has been said, Using a slicing motion would help but you could also knape a flake with a steeper edge. The flake shown were paper thin. Find a flake with a 45 to 60 degree edge. you can also add beveling to further strengthen the edge, but that's a more advanced technique
This reminds me of Micro diamond blades that surgeons use. They can't induce any lateral movement on the tools blade under friction or it could ruin the diamond blade. Cutting requires friction generally too, which is why you can take a relatively sharp pblade and press it to your skin without drawing blood untill the moment you apply friction to the edge.
brittle and soft cutting edges do not push cut well if they can even do the cut to begin with. obsidian is always going to be better at slicing. the testing method of the bess system isn't appropriate for the material being tested. also remember that the angle of the edge doesn't exactly mean one is sharper than the other. obsidian even at 18 degree angle can still be insanely sharp and have enough support material backing the edge to not just flake out like viewed in your tests.
In high school history class, our teacher, Mr. Williams, was really into his subject. He brought in some obsidian and chipped off a piece. He explained that it formed a crazy sharp edge, so sharp that they'd been used as scalpels in surgeries. He passed the piece around and from behind me I heard, "oh..." Someone had lightly run it over his palm to get an idea of its sharpness, and was excused to head to the nurse's office... trailing blood the whole way. Said he didn't even feel it until seeing the blood.
I might be wrong, but couldn't the geometry of the cantilever tip affect the measurements? While the tip itself is probably plenty small with a radius of like 10nm, you risk running into issues if the indent measured is too deep, as the angle of a razor and probably also the flint and obsidian edges might be smaller than the angle of the cantilever tip. As I said I might be wrong. Haven't worked with AFM for several years so might misremember stuff.
If obsidian is typically used on cutting flesh, and if it's prone to fracture (or self-sharpening via cleaving - resulting in a serrated edge), I wonder what the long term consequence of these micro-sized obsidian pieces being left in the flesh is? Or would it only be used in non-living things (e.g. in research)?
A lot of people in the comments are bringing up the use of obsidian scalpels in surgery. Yes, they're used. But only because of it's non-magnetic properties in contrast to common steel alloys which is an important factor in procedures requiring the use of certain imaging techniques that can be skewed by ferromagnetic tools or made simply impossible (like with MRI due to the magnetic fields the machine induces)
These tests are interesting, but entirely fail to control for any number of material properties that could distort your results. An obsidian edge certainly isn't going to stand up to a material harder than itself. Even against lead, the edge will deflect, and fracture or leave a distorted imprint.
It’s crazy how many people are throwing out comments about how obsidian shouldn’t be measured by pressing down on a wire. It’s almost like he explains that exact thing and says there should be different tests for different cutting applications at the end of the video
If you moved the Obsidian blade in a diagonal motion it will successfully cut - since you need the pateral motion in the direction of the blade to overcome the brittleness
you could try slicing, that may be better to see the viability of obsidian as a blade. though the setup may be a bit tricky Edit: if I am remembering correctly obsidian is used in a cutting edge for scalpels
There have been some publications about the comparison of obsidian edges and scalpels and there has been no advantage of obsidian so far, neither in cutting, nor healing.
i sliced my ankle open while napping obsidian. a chunk launched straight down and cut the flesh on my ankle bone so swiftly i didn’t even realize it happened
I don't think that you're quite done with this one yet. You've probably already heard from someone who's worked in Histology. But, in case you haven't, here's some background. Some (many) years ago I did such work. Pathology samples are "fixed", embedded in wax blocks, sliced into really delicate slices, these are then floated (and also have the wrinkles flattened out) in a warm water bath. From here, the most promising looking slices are lifted onto a glass slide, dried, dewaxed, stained, and coverslipped. As I recall, we used to cut at around 8 microns. I think that 4 is the absolute limit for steel blades. The blades at that time were like an oversized cut throat razor. they were honed and lapped by machine on a glass plate. These have since been superseded by an oversized analogue of an injector blade, more for convenience than performance. BUT, neither of these provided the best blades. These were made from a special glass bar, which was broken on a machine made for the purpose. With these, slices could be made as thin as one micron. I might add that everything to do with glass knives is too much of a pain in the arse for all but the most fastidious. More blades were thrown away than kept for use. The edges were in every case though, much more even than shown on the obsidian here. This is hardly surprising though. After all, in the one case, you have a regularly shaped object of uniform composition held firmly while very precise pressure is applied. In the other, you belt an irregular lump with a rock. I suspect that you may have to ring a lot of labs before you find one equipped to make glass blades. But if you do, I reckon that they'd be delighted to supply you with some, once they know what you're about. Cheers.
The "napped" edges should be serrated in all along the edge in different planes and sometimes in opposing plane. That could be snagging along a wider area then the "ideal" edge.
The tungsten emitter of a scanning electron microscope is a metal point etched down to a single atom at the tip. You literally can't get sharper than that.
a different method to measure it, pulling each blade across a reference material like the lead, with a fixed static load, maybe even a slight rotation to it to mimic a true slicing motion that these types of blades would be best suited to
there are even devices to make glass blades for cutting samples for transmission electron microscopy. No need for fancy obsidian, only flat glass needed. And you can make finer cuts than with basically anything else except for diamond knives.
I think you've missed an important part, when ancient man cut something with obsidian, he did it in motion, like when you cut something with a knife or a saw, that is, he didn't just touch it, but moved it back and forth like a saw.
It’s interesting that obsidian can get that sharp, but it is too brittle and too difficult to get a large uniform edge; i.e. it is impractical for most real-world applications.
I regularly sharpen knives, with a jig, and get extremely consistent results. I have also knapped obsidian, and i will say that occasionally youll produce damn near scary sharp edges of obsidian. Like shave hair and not even feel it sharp, sharper than i can intentionally sharpen knives sharp. They arent the thinnest pieces either, its just the ones that come to a consistent edge.
Well when I was in college we used broken glass to cut sections thinner than a single cell for the electron microscope and since obsidian is glass then yes it probably is one of the sharpest edges possible.
Nice settings! A cutting proces allways involves moving the cutter at the same time putting some pressure on it... Try to cut thick leather with a razoare blade and than compare it with a obsidian blade...
I think that your biggest problem is in fact the strength of the materials. Steel withstands the wire test because it is structurally very strong. Its strength can be adjusted by tempering. That's why they use it for blades! We take it for granted but its a very high tech material. Glass on the other hand despite our 'perception' is a soft material and does not withstand the wire test because the edge deforms under pressure. As would non tempered steel The wire is possibly harder than the glass. If you cut materials that were softer than glass such as mammoth meat you might find that it performed better. (good luck on finding the mammoth meat).
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bro this is to much tech we ain’t trying to split hairs, oh wait
The real question here is why your mate doesn't own a pair of nail clippers.
Obsidian Sharpness Enchantment
@@matthewhopkins7042 He bites them
Why did not you employ electron microscope like you did in the other videos? 0.5 um is optical range, and also it seems to reflect more the shape of the cantilever rather than the shape of the blade, besides the imprinting process makes another unknown error into the result.
Sharpness can also be measured on the opposite axis, dragging the edge as done if cutting a tomato. You never see a chef push a knife through a tomato. Rerun the same test with a sawing action and your results will drastically change. Measure y over x with x being a fixed distance.
For a polished edge like the chisel, including a sideways motion will simply have the effect of making the sharp angle sharper. It's exactly like the trick of bicycling up a hill: compare straight up vs going diagonally from the left side of the road to the right side of the road as you ascend the hill. In the latter case, you covered a larger distance for the same rise, so the hill seemed less steep.
IOW, for modern (non-serrated) blades, the sawing action does not change the characteristics and if you want to include a sideways motion while cutting we know how that affects the sharpness number you started with.
For a napped edge, it may contain microscopic serrations, which contain cutting edges facing different directions. Here, sawing does not make the blade angle sharper but engages a micro-blade at that angle. Being able to cut through a material using saw teeth is a ripping action, different from sharp cutting. That opens up a whole new level of complexity in how to measure and quantify. But, it won't split a hair that way.
Note that kitchen knives are purposefully not very sharp, compared to a woodworking chisel. By only using an 800 grit to finish, it leaves a toothy finish on the soft metal at that scale. This grabs the tomato skin when you move across it, and optimizes the knife for cutting foods, in general.
@@JohnDlugosz if I understood your logic in the video, you stated that the obsidian had broken. Therefore it couldn’t be nearly as sharp as the metal. However, even the sharpest metal blade is at best several molecules wide, and the obsidian can be a single molecule wide. Therefore it is fragile. I was simply proposing that you reduce the amount of pressure at any given point of contact by moving across an angle, thereby allowing a greater cutting action at a lower force, preventing the fragile blade from breaking.
Pretty sure a sawing motion would be make the data too inconsistent. Unless you have a very precise robot arm that can replicate the exact motion and apply the same amount of pressure in each test run.
@@tedwintheslyfox9382 uhhh an Arduino, a stepper motor and a small gear setup would suffice, so many rotations over so many thou an inch over x time, what kind of engineer are you?
@@DurokSubaka If you could grind a straight flat edge, that would be the case. But the natural napped edge is like a rugged coastline. Moving sideways will simply engage a different micro-edge that's facing that direction, and buckle and smash it.
But more seriously, applications for obsidian are typically scalpel tools. So it means that instead of a push stroke, it's a gliding stroke across a surface (slicing). Your setup measured sharpness of something pushing; would gliding change the parameters of the problem of sharpness?
it also fails to address obsidians self sharpening via edge fracture. It's not a flaw, but a feature of obsidian as opposed to metal, where instead of becoming dull, it becomes serrated with new sharp facets
@@Azmodon but the edge did fracture and only got more blunt?
Came here to make this exact same comment. I'm sure the obsidian would *cut* hair with a slicing stroke. Splitting hair with a push stroke is a different question.
Obsidian is serrated. Is not sharp like a razor blade for example
Would be interesting to be able to capture images that show how serrated it is, as well as be able to compare it to the granular structure of flint (chert and chalcedony).
Finally, someone is splitting hair on the internet!
Alright, credit where credit's due: that's a good one
no because you see they're actually splitting multiple hairs, not a single hair. hope this helps
@@sam-is-a-human I think you're splitting hair here. Hair is the plural of hair, as hairs is.
@@michelhv *pushes glasses up nose* well actually, hair is the plural of hair when it's every hair on the head, hairs is plural anytime else.
@@sam-is-a-human Hear hear! Hair here.
Beyond the issue of pushing vs dragging, you may also not be producing the obsidian blades the right way: they weren't simply knapped. I do stuff with Mesoamerica (Aztec, Maya, etc) history and archeology, where obsidian was widely used for tools and weapons. I'm more informed on things like Architecture or aqueduct systems then obsidian production; but the way they did it is the prismatic blade method, which isn't simply striking off sharp shards off a starting stone, but is an actual systematic process to work a "core" piece down to produce single even blades with an insanely fine edge.
This wasn't a static practice either, there were innovations in obsidian working and prismatic blade production with how the core is struck even only a few centuries prior to Spanish contact in the postclassic period, by which point the region has already been heavily urbanized with city-states and empires for thousands of years and already had a robust obsidian industry. Those innovations in blade production may have actually been what allowed Macuahuitl to pop up in the form the Aztec used them, since it could produce consistently evenly sized and shaped blades, wheras before that the types of weapons used in Mesoamerican warfare didn't tend to have evenly lined edges like that.
I can't really go in more depth on this, as I said, obsidian production isn't one of the Mesoamerican topics i'm super informed on (ask me about how cities were laid out or how Aztec political systems work and then I can give you 12 paragraphs!) but yeah, it may be worth looking into prismatic blade production worked.
Their practices were focused on making the edge more durable, not sharper. The sharpest edge of obsidian (that "one molecule thickness" edge), or any knappable material for that matter, is from the flakes that appear paper thin when removed. Obviously a paper thin edge is all but useless for cutting due to how fragile it is, so instead a compromise is used to increase the edge thickness and supporting material to a point where it can handle impacts and repeated cutting without it being a one and done affair. It's a difficult process but most anyone can pick it up with enough time and materials and patience. Knapping your own tools and points is a great way to keep that tradition alive so the knowledge is never forgotten.
What do you think of the theory that Aztec originated from Utah?
@@tylermestek4790 I mean, there's some truth to it, but it's a little misleading: The Uto-Aztecan language family, which Nahuatl (The Aztec language) is a part of, does originate in the Southwestern US. But that being the origin point for the broader language family doesn't mean that the various Nahua groups were hanging out in the SW us directly before they migrated into Central Mexico and became Aztec civilization: Uto-Aztecan languages spread gradually and Nahuatl came about much earlier then those migrations. While we don't know for sure, most researchers and most of the evidence suggests that the Nahuas were in the Bajio region of Northwestern Mexico (So Nayarit Jalisco, etc) when they started to migrate into Central Mexico. The movement of people/languages from the SW US to the Bajio area would have happened centuries or thousands of years before that.
But to be honest the development of Nahuatl is not one of the topics I am most well read on, so I can't give many specifics other then what I just said and even then some of that is debated. But no researchers think that the Nahuas travelled directly from the Southwest to Central Mexico: That's not one of the valid competing intepretations, what is is where else in Northern Mexico the Nahuas would have been, how much earlier the spread from the SW to northern mexico was, or if Nahua migrations from Northern Mexico to Central Mexico may have predated the 13th century AD migirations that Nahuatl language accounts assert they happened in.
That being said, there is evidence of trade between Maya states and the Southwest US, where Maya merchants brought Macaws, rubber balls, etc up to trade and you can see macaw skeletons, rubber balls, and some ballcourts at Oasisamerican (Pueblo, Hohokam, Salado, etc) sites in the Southwest. It used to be thought that the Mesoamericans were trading those things for turquoise, but recent research shows all/most turquoise used in Mesoamerican art was sourced locally inside Mesoamerica.
@@Skinflaps_Meatslapper There is no point in trying to make obsidian flakes reusable or durable, the qualities that give it the super sharp flakes is the same qualities that make it brittle. Even early humans would carry multiple stones to have access to fresh flakes and constantly need to re-knap their knives. It's just a quality of the rock so it's pretty pointless to make them more durable for a sharpness test.
@@themodernninja8074 Kind of the point I was trying to make. Can you produce an edge with obsidian that's even sharper? Probably so. But there's always a tradeoff, even with steel, between sharpness and durability. The problem with obsidian is that you'll never get to use that full sharpness on anything because it'll flake off the first time you try to cut with it, leaving behind a less acute and duller edge before you're even done with the first cut. That's why the flintknappers of the past were more focused on making a less acute and duller edge that had more durability instead. A knife or point would be useless to them if it was damaged on the first cut and needed to be sharpened again. The obsidian tools they made would hold their edge remarkably well for how brittle the material is, but they still needed to be dressed and resharpened often. Based on evidence and micro flakes at butcher sites, archaeologists believe that they dressed their cutting tools a few times in the process of butchering larger animals such as a bison until they became too dull to use, and then switched to another when they could no longer expediently dress the edge. Later on at camp or whenever they had the time, they'd re-profile the entire edge or repurpose it for something else. They certainly didn't last a long time with normal use and they went through a LOT of them, and that's a big part of why you can find so many of their tools in abundance all over North America. It's a big part of why natives in the West happily abandoned their flint tools when steel knives became available to them via traders and whatnot. They were intimately familiar with flintknapping and knew the limitations of stone tools. The primary reason why they continued to knap was simply to preserve their knowledge and way of life.
Napping is also an ancient process used to sharpen your mind.
I mean, I guess you're right.
LOL Underrated Comment Fr
Based ❤
That's adorable!
As someone who works with obsidian, it is extremely sharp. If cut with a piece of it, it only starts bleeding a few seconds after the initial cut. But I still continue to make arrowheads out of it.
What kind of Obsidian is being used in the video? Is it worth anything ?
@@LucyWoIfit's literally just lava from volcanoes, melted rock glass!
I recall a Nat Geo article i believe about obsidian scalpels being used in surgery cause the cuts were so fine they healed much faster
It was done experimentally, and the results were suboptimal compared to modern tools.
There was a company that made and sold obsidian scalpels for a while but they never really caught on.
Sounds incredibly dumb. It can easily chip, then you just have a tiny sharp piece of stone slicing your insides.
I asked an eye surgeon if he used obsidian blades. He said no they use silicon blades. Diamond blades are available but not used. When the techs sterilize them after surgery they chip them and they are then useless and are discarded
Obsidian *can* achieve a sharper edge, but doing so with any sort of consistency, or more importantly durability to handling and use, is another story.
Debatable. There are jigs and cbn/diamond plates with as low grit as you want, and you can get a steel edge far superior and sharper than glass + tougher.
@@em4703you're ultimately limited by carbide grain size
Brittleness is a highly-prized aspect of obsidian. Prey knock out the shafts soon after they are hit. You WANT the shaft to break, and the projectile point too. If it falls out - wounds close, blood clots. Prey runs miles before being lost. But how far is it going to go with broken pieces of glass working its way deeper towards/in internal organs with every step? Not far.
Easily made, easily replaced. Obsidian tools were made to break - and that was great!
Hey, plastic surgeon here.
Obsidian scalpels are a real thing. Yes, they are sharper than any other steel edge. The obsidian scalpels are very difficult to find, but I use them on occasion. The obsidian blades are ground, and polished, during manufacturing. How? I don’t know. But they are all uniform in size, thickness, and cut through any tissue with almost zero resistance.
Obsidian scalpels are actually scary to use. And that is coming from a surgeon.
If you want some, let me know. Happy to send some your way.
Crabtree made obsidian scalpels that were used for his open-heart surgery. The trouble in these tests are multiple. As the narrator pointed out initially, the obsidian is brittle. The second error is more subtle. The "sharpness" test as employed here is simply an attempt to push the edge through the wire. That is fine for any material edge that is arguably as tough (not brittle) as the wire, but plainly isn't going to work if the edge to be tested is brittle and crushes. Also, when used as "recommended," most knives are not simply employed like a wedge. They are drawn or pushed at an angle to the surface being cut. The effective angle of the cutting edge is less than the edge angle measured perpendicular to the edge. Last, the ultimate fineness of an edge is limited by the grain structure of the material. The coarser the grain, the duller the maximum possible sharpness. Obsidian has no grain structure, nor does any other glass. This why, for extremely delicate surgeries many surgeons employ scalpels edged with glass or diamond. However, those same surgeons would not trouble with obsidian in a wood working context.
It's also important to note that the roughness of two tissues when stitched back together increases the efficiency of their ability to seal and heal. So even if we came up with some sort of super material that sliced through tissues literally perfectly, splitting molecules apart or whatever, we wouldn't want to use it on anything we intended to put back together.
@@Marcara081 Roughness would coorrelate to increased trauma to the tissues, which enhances physiological response I think. Evolutionarily, nearly all trauma a body responded to would involve more damage to the tissues at the site, whether it's a scraped, or some sort of puncture like a bite. A cut from a really sharp blade, regardless of material, will separate many cells where a comparable scale injury from a rougher material will rupture cell walls. That releases chemical signals to the surround tissues. It's why cuts from glass bleed so profusely.
@@theeddorian Tears in tissues heal faster and with less complications than cuts, sort of like breaking a popsicle stick in half and then shoving the jagged break back together, rather than cutting it in half with a saw. A jagged break causes the material to interlace with itself and provides much more surface area to join together, just like a tear in tissue will interlace back with itself and heal faster. The medical community doesn't actually agree that finer cuts result in better healing these days, but they did hold that opinion about 50-60 years ago. Precision cuts are only necessary today for minimally invasive surgery and a sharper blade is required, however, it's not the incision itself that benefits from a sharper blade, rather it's from the smaller incision of minimally invasive surgery that allows it to heal better. If you can get away with a 2mm incision rather than a 2cm incision, there will be less to heal...but your blade has to be up to the task of making a precise 2mm incision.
@@Skinflaps_Meatslapper As someone who knaps obsidian, and who works wood, and who sharpens tools and knives by hand, my experience is contrary to that. Low trauma cut from really sharp steel, or glass edges, closes quickly when bandaged properly. Such a cut also heals cleanly and with less scar tissue. Trauma from tears, scrapes, and rips ceases bleeding more quickly. Usually, since the cut from a sharp edge has less surface area, less tissue surface is involved in healing. I asked an ER doc about that years ago, when I notice that some scars I've had since I was three or four are still obvious, while the scars of serious cuts from chipping stone and accidentally bumping the edge of a freshly sharpened knife were completely invisible.
Its surreal seeing my great uncles heart surgery talked about by someone i don’t know in a TH-cam comment section XD
As a bit of a self-appointed expert in sharpness (I'm a bit of a straight razor and honing nerd) there is a very interesting love triangle regarding sharpness. First is the thinness of the edge of course, second is the brittleness of it as you mentioned, but there is also the edge ANGLE that is critical. Basically the 'game' is to get a sharp edge that isn't too brittle by increasing the edge angle. For example, for straight razors, a 'too sharp' razor will 'fold' (or break, if the allow is particularly brittle) it's edge very quickly so is useless -- a 'too blunt' edge will mostly pull hair which makes the shape very uncomfortable.
With straight razors, an edge that is too thin can be 'bevelled' by placing table (like, electrical tape) on the back of the blade and redo the edge, to increase the cutting edge angle.
Multi angle bevels are fantastic. Particularly if you work your initial bevel to a fine edge and then just barely work the secondary bevel down, to the point that it's microscopic. You get a larger angle on the edge so it's more durable, but at the same time you reduce the contact area of the bevel on the object you're cutting...instead of the entire bevel sliding across the cut material, it's generally only that micro bevel that's seeing any friction so it cuts with less resistance. I work mostly with knives, so my bevel angles are far greater than a straight razor, but I can get close to that level of sharpness stropping with kangaroo leather and 1um diamond paste.
I have gotten a score of 100 with obsidian when it is knapped skillfully into a blade. The shape matters a lot and you need a skilled knapper to produce them.
It would be interesting to see some experiments of stonemasonry chisels of different materials and edge geometries and how the "cutting" action actually happens.
I'm with you on wanting to see other cutting tools checked this way, ie more methods than just bess testers. The microscope view of the cut happening is very cool.
As far as the masonry chisels go, I think that would be interesting to see, but I do not believe it is "cutting" in the sense we tend to think of. I don't use hand chisels at work, but when we drill into concretes and natural rocks (metamorphic and igneous primarily, I think), we use either rotary hammers, which take a carbide chisel point embedded in a normal looking drill bit. That carbide chisel is decidedly *not* sharp normally, and uses the power tool to strike the stone, imparting around 10 lb/ft per impact over the very small chisel area, around 3000 times per minute, and then the rotary action is just clearing the fractured chips up the flutes and out of the hole; alternately, we use diamond hole saws/core drills to abrade away the rock in a fine dust (this actually need active cooling with water, unlike the hammering process). The caveat to that is there are specialty concrete bits designed to cut through rebar in reinforced concrete, and these have a very different carbide striking edge that is also needing to cut iron in this application, and those do tend to be sharper, and have a much tighter radius point at the intersection of the (usually) quad point chisel.
My guess for handheld masonry chisels is they operate the same as the rotary hammer method, albeit much slower, with much higher energy imparted per blow, and the edge is being used to concentrate where you are causing the fracture, and the vector of the force, giving a significant level of control compared to a rotary or demolition hammer.
'and how the "cutting" action actually happens.'
Having split some pavers and granite rocks by hand for the patio, I can tell you this easily.
Doesn't matter how sharp or hard you make the chisel point, it's quickly going to round over and make a narrow but relatively blunt edge. You're hammering the edge against stone, it won't stay sharp.
The cutting action is really peaking a large amount of force into that still relatively narrow edge, and locally creating small fractures and some grinding. Eventually you send fractures enough through it that it splits entirely.
Go watch videos of splitting stone by hand and it's all basically a fracturing process, not really 'cutting'. Then there are softer stones like marble etc, when carving that you're still setting the chisel at a shallow angle and grinding and fracturing it off.
And tool and saw cutting stone is much more related to narrow grinding.
Only very soft stone types with a hard sharp edge might do something more like actually cutting the stone apart.
A sharper chisel will cut your stone a bit better and faster at first, but it's more about concentrating the fractures better into a narrower space than that it's really 'cutting' the stone better. Sharpen up a masonry chisel and try some, it is very interesting to do. But you'll quickly stop thinking of it as cutting like a knife, and much more like fracturing/grinding under that chisel edge.
Yes this is so. I did the stone masonry course at Bath, and it's what you are told pretty much. A ''hard'' stone is characterised as one that fractures, the chisel edge is controlling the angle of attack and force, producing a fracture that deepens at that angle , and then as the force can't go right through (unless perpendicular) immediately ''spoons'' back up to the surface...your chip. A ''soft ''stone appears to cut, but it is really a micro-crumbling in front of the edge. Cutting non-brittle material is completely different ! And that's where slicing comes in, as the material can be used against itself. I bet the obsidian would win.
@@ModelLights
"Obviously it is sharp enough to cut hair, but none of my obsidian chips had a fine enough edge to split one." There ya go
Super cool analysis! Love to see this mix of machining and AFM 😍
This is stunningly fascinating presentation, regardless of the subject matter.
This is exactly what Tim Berners-Lee had in mind when he legged it down the patent office.
Hardened tool steel, if done right, can be both harder and tougher (less brittle) then minerals of silicone dioxide. Flint actually has a granular structure (ranging from microcrystaline to cyrptopcrystaline, as formed from diatoms), which is why it's assumed to be less sharp than obsidian.
How much would that cost though? Surely just the certification of the process accuracy would make it extremely expensive compared to silicone dioxide?
@@SkywardSwag I don't know if you're talking about blades or AFM probes, but I just thought of something related to this that may or may not make sense.
The reason silicon dioxide is used for AFM, and not tool steel, is because the tip is vibrated at a VERY high frequency. And vibrations in a material can induce harmonics, which can actually heat it up. Tool steel, relatively speaking, is not thermally stable - its thermal expansion coefficient is a bit over 10^-5/K. Silicon, on the other hand, has a coefficient of 5*10^-7/K - that's twenty times smaller than that of tool steel.
When you're measuring on the level of angstroms and your probe tip is a nanometer in two in diameter, a millimeter long probe assembly can expand a whole nanometer when exposed to just a fraction of a degree of change in temperature if it is steel. But if it is made of silicon dioxide, that thermal expansion can be limited to under an angstrom.
This is also the reason why obsidian works great as a slicing tool, but not as a cutting tool - and why tool steel, even if it keeps its sharpness, will eventually roll the edge on an atomic level - simple contact with the skin would make the edge heat up and expand, and when it contracts, the edge radius will change.
"if done right" the point is to use something not manufactured
You explain everything with such care. You manage to explain even rather complicated measurement methods such as atomic force microscopy. Take pride in that, loved the video! Oh, and the visuals are also gorgeous, you have a way with cinematography.
8:32 I think because the pressing of the blade was done by hand instead of a true, constant 90 degree downward angle, which made the impression in the lead inaccurate and misshapen. A slight pull of the blade towards the camera; a tilt, has occurred, which pushed the lead cross-section to the left, warping it.
I love learning about edging!
Same! I'm edging right now too!
brain rot goes crazy
...
What the actual heck…
@unknownuser_7012 ☝️🤓
1:39 activated my Google assistant xD
Indeed, it would be interesting to see how well the obsidian cuts a softer material, like planing a piece of wood, or slicing a bit of some kind of flesh...it might well be that planing a piece of pine, measuring the thinnest slice, as is done in Japanese planing contests, might yield an interesting result...
Obsidian would probably chip out on pine pretty quickly
I know this isn't the point you were trying to make, but I only just learned that planing contests exist... I need to go look this up now.
@@geoffreyentwistle8176 those competitions yield some impressively thin and even shavings.
Question: why wouldn't you put the edge indent on the disc after it was mounted to what it was going on?
Simply knapping a piece of flint will usually not result in a razor sharp edge.
However, due to the structure of obsidian crystals, and the properties of obsidian itself, it can effectively be sharpened to a (near) mono-molecular edge.
Common uses for obsidian are surgical tools used on soft tissue, such as scalpels.
Hardness, toughness and sharpness are all independent from each other, as is the capacity for one object to hold any one of these properties.
What i'm saying is that your test method for sharpness isn't a test method for sharpness.
It's a test method for all three.
Crystalline structures are WAY too fragile to be subjected to these kinds of localized static pressures, so even though it can be much sharper, it will not ever come out on top of that test.
Therefor: _Your test method is inadequate._
I am SO DISAPPOINTED they didn't do a drag test... as if there was no difference between smashing and cutting...
Very fascinating video! I did not understand much of the terminology but I do understand the testing and what you sought out to understand.
wow! proud of you to attempt such an experiment. love it. reminded me of TEm in late 80s on silicon devices....
Looking at sharpening from grinding wheels etc, but read a comment the other day from someone who use to make obsidian blades for eye surgeons back in the 70's and probably into the early 80's. Said it was very expensive but it was what they used, so you can bet it was the sharpest thing that was reasonably practical even though expensive.
Said it largely got phased out by lasers.
Me, in the kitchen doorway, holding a cup of water: **sipp**
TV: autoplays this
Me: guess I'll stay here transfixed for 10 minutes
Please fix sibilant issues with EQ of audio. It's around 5 kHz to 8 kHz ish.
Good call. It really is a very simple fix any editing software can do.
Pro cutter here. I earned my chops through 8 years of a commercial kitchen with a chef's knife and 4 years in an Aikido dojo where you use cutting techniques while unarmed.(think of how a river can slowly cut through a mountain or how you could, "cut," through a wooden table with your open palms, using lots of time and sandpaper.
Hardness alone can, "cut," but a straight(what I'm going to call focused) edge will magnify the cutting effect at the cost of damage to the edge.
I would argue that a square blade that is incredibly hard with a really clean edge can do incredible levels of cutting, while reducing the damage to itself. Heck you can probably even cut with an obtuse edge if your blade is hard enough.
There is also a bit of a thing with proper technique. Drawing an edge creates a slice and a slice will greatly increase cutting power over a chop. In many ways using a chisel is also a type of slice, with the greatest cutting happening during the sliding of the chisel and not at the start or and of the gouging stroke.
Great video, very interesting. My only quibble is the practical difference between chopping and slicing. A very thin but weak edge is capable of slicing but not of chopping - anyone who's had a paper cut will bear this out. The obsidian would work quite well if used with a gentle slicing action. I imagine that people using flint and obsidian tools soon discovered this.
However sharp, a broadsword worked mainly by smashing bones, not cutting flesh. By way of contrast, a Japanese samurai's sword was a slicing weapon.
The extreme hardness of an obsidian edge makes it completely unsuited to chopping, but I'd be interested to see how it performed as a scalpel.
Seemed like an insightful comment to me, but no up votes besides mine? I thought the idea of a slicing test was a good one. I was trying to think of a test where greater sharpness of the obsidian could be demonstrated by cutting something. Your idea seems like a good way of accomplishing that.
No up votes because it's nonsense. A broadsword cuts just as well as a katana, absolute nonsense to call it a smashing weapon and a katana a slicing weapon
Katanas should not even be mentioned in this context
@@Tom--Ace I saw the comment more about thinking of a way that a super sharp but super brittle cutting blade might demonstrate cutting superiority in some kinds of situations and that a slicing situation might be one of those situations.
I'm not familiar with sword issues. In my ignorance, the sword analogy seemed reasonable to me.
Thanks to Tom-Ace's comment I watched the video again and read @EleanorPeterson's comment again. One idea of a situation where the obsidian might be better would be at cutting through soft material. My thought is that if instead of wire the sharpness tester used a thin nylon line the obsidian would cut through it with less force than any metal cutter.
4:19 For comparison, a strand of DNA is 20 Å wide...
Amazing!! Was glued to the screen for the entire video.
This is such a nice high quality video with high value content. Thank you and keep up the good work.🎉
The "point" of obsidian - weaponry. 1) Sharpness but also 2) Brittleness - the 2 most desirable features. (Which explains why copper tools were developed in N America, but didn't catch on.) Obsidian spear/arrow heads are weapons of hunting/war. In an age before beasts of burden, (all on foot! even packing out 200 lbs of meat per person!) you WANT the projectile point to do 2 things, which bring the game down faster. (You don't want it running miles away, into bogs/cliffs/inaccessible areas or found so late the meat spoils.)
1) Penetrate deep; which sharpness allows.
-For maximum organ damage/ wound enlargement. (As the prey runs, each step shuffles the rock/glass pieces inside like a tumbler. Cuts more tissue/enlarging wound, severing vessels/arteries.)
2) Breaking in the wound - ensures the cutting edge stays in the prey to continue the damage.
-The shaft is like a big stick, it WILL get knocked out due to the prey writhing/rolling/banging it on trees. You want a BREAK.
-Non-breaking projectiles that don't penetrate far (less sharp,) can simply fall out with prey movement. The wound can close, blood can clot. Prey can flee to Timbuktu before death.
Did they really want projectiles to break? Yes. Trade with others. Get your skilled knappers to tap a few times - boom, replaced.
Remember - obsidian tools are "art" to us modern folks. To the ancients - disposable, replaceable, common tools. Meant for USE.
"Oh it's so pretty I kinda hope it stays intact and falls out - so we lose our kill we've tracked for 9 days across a glacier and our family is at risk of starving" - said no ancient ever. :)
They'd look at copper tools. Less sharp. Pain in the *** to mine/smelt/craft. Soft. Really soft, yet, bendy, not brittle. Falls out of game into grass - oh who cares if we even find it? Let's go back to stone/glass!
Presumably the action of "slicing cut" (dragging the entire sharp surface on object) instead of "wedge cut" (forcing one sharp surface down), kinda help the brittle edge from breaking.
The name "obsidian edge" is fire af🔥
I thought I'd see more comments about "Cutting Edge" science. I'm not mad, just disappointed.
thank god. after years of knowing that obsidian makes the sharpest edges I can't believe I finally see a good video covering the topic. this had me intrigued for the longest time.
Thank you for this insightful video . I learned that for a push cutting action, steel razor are much better suited for this. It flexible nature allows the razors edge to withstand some buckling caused by the force needed to puncturr or slip open the material. This force intuitivly is the peak force of the cutting action because creating a cut or crack in the material surface will cause stress will concentrate in the material. Theerefore the blade will have an easier time pushing wedging apart the material once this crack is made . And it made me think about why the obsidian preformed the way it did. Its clear the edge if the obsidian blade was too thin to with stand the the force need to "puncture". It seems puttin a very small amount of normal compression stress on the on an obsidian edge that thin causes it the buckle, and therefore crumble because of its extreme brittleness. I agree, a slicing motion instead of a pushing motion a better way to test the obsidian. . Which makes sense. You ideally you only want to put shear force against the blade. With an edge that thin, the face it is just a jew atoms in width. That an incredibly small area so the shear stress would be so minimal preserving the sharpness of the blade. Any small amount compression stress will cause the blade to want to buckle abd there for crumble.
I can belive they got Radio Demon as a host.... Nice to see Alastor.
This is just... Awesome. Tremendous work!
Taking it to the next level as always. I love your videos!
i think one of the 'applications' you're talking about is Slicing. slicing being much different than just pushing. The obsidian anecdote comes up mostly in context of cutting human flesh. (historically violently, modernly medically) and from what i remember, it's that obsidian (lacks application in medicine because of the tendency to shatter, but maybe not if our bodies can deal with it) maintains edge hardness longer, and maintains slicing sharpness longer (due to breaking and new edges still being sharp). and also that obsidian is sharp enough to slice cells rather than tearing them. i don't know how much of that is actually true, but i think it's worth consideration.
As has been said, Using a slicing motion would help but you could also knape a flake with a steeper edge. The flake shown were paper thin. Find a flake with a 45 to 60 degree edge. you can also add beveling to further strengthen the edge, but that's a more advanced technique
This reminds me of Micro diamond blades that surgeons use. They can't induce any lateral movement on the tools blade under friction or it could ruin the diamond blade. Cutting requires friction generally too, which is why you can take a relatively sharp pblade and press it to your skin without drawing blood untill the moment you apply friction to the edge.
Been waiting for this video for decades, since I first heard about obsidian blades.
The atomic force microscopy bit was fascinating!
brittle and soft cutting edges do not push cut well if they can even do the cut to begin with. obsidian is always going to be better at slicing. the testing method of the bess system isn't appropriate for the material being tested. also remember that the angle of the edge doesn't exactly mean one is sharper than the other. obsidian even at 18 degree angle can still be insanely sharp and have enough support material backing the edge to not just flake out like viewed in your tests.
Does Obsidian Really Form the Sharpest Edge? 6:42
In high school history class, our teacher, Mr. Williams, was really into his subject. He brought in some obsidian and chipped off a piece. He explained that it formed a crazy sharp edge, so sharp that they'd been used as scalpels in surgeries. He passed the piece around and from behind me I heard, "oh..." Someone had lightly run it over his palm to get an idea of its sharpness, and was excused to head to the nurse's office... trailing blood the whole way. Said he didn't even feel it until seeing the blood.
I might be wrong, but couldn't the geometry of the cantilever tip affect the measurements? While the tip itself is probably plenty small with a radius of like 10nm, you risk running into issues if the indent measured is too deep, as the angle of a razor and probably also the flint and obsidian edges might be smaller than the angle of the cantilever tip.
As I said I might be wrong. Haven't worked with AFM for several years so might misremember stuff.
What part is that hair from?
that was informative, keep at it!
Great video! Every time TH-cam would recommend me one of those obsidian simp channels I would roll my eyes. Keep up the great work.
If obsidian is typically used on cutting flesh, and if it's prone to fracture (or self-sharpening via cleaving - resulting in a serrated edge), I wonder what the long term consequence of these micro-sized obsidian pieces being left in the flesh is? Or would it only be used in non-living things (e.g. in research)?
Nothing really. Just like people with pencil lead stuck under their skin. The body simply encases it and it remains there for life.
Fantastic video. About how much was the AMF tool you used?
"The equipment needed to measure our analysis are expensive. So we made it ourselves." This cracked me up
Why people getting angry just because an obsadian doesn't perform well😂
Ancient Egypt Stans
A lot of people in the comments are bringing up the use of obsidian scalpels in surgery.
Yes, they're used.
But only because of it's non-magnetic properties in contrast to common steel alloys which is an important factor in procedures requiring the use of certain imaging techniques that can be skewed by ferromagnetic tools or made simply impossible (like with MRI due to the magnetic fields the machine induces)
"then i smahed them with my wooden bat. Because geologist only sees rocks and minerals."
“Shang, you’re outfit is so sharp, it could pierce an entire fire nation battle class ship, leaving millions to drown” -Azula
This is some cutting edge technology!
These tests are interesting, but entirely fail to control for any number of material properties that could distort your results. An obsidian edge certainly isn't going to stand up to a material harder than itself. Even against lead, the edge will deflect, and fracture or leave a distorted imprint.
It’s crazy how many people are throwing out comments about how obsidian shouldn’t be measured by pressing down on a wire. It’s almost like he explains that exact thing and says there should be different tests for different cutting applications at the end of the video
absolutly, I've never seen/thought Obsidian would bend rather than shatter
cry
This is youtube pro
If you moved the Obsidian blade in a diagonal motion it will successfully cut - since you need the pateral motion in the direction of the blade to overcome the brittleness
What brand of razor blades were you using?
you could try slicing, that may be better to see the viability of obsidian as a blade. though the setup may be a bit tricky
Edit: if I am remembering correctly obsidian is used in a cutting edge for scalpels
Didnt expect someone to bust out an AFM in such a meme video
maybe, but against a geologist a wooden bat is more effective
😂😂😂
I wish I could watch this video with Christopher Dunn 😢
How cheeky building your own edge tester 👍
There have been some publications about the comparison of obsidian edges and scalpels and there has been no advantage of obsidian so far, neither in cutting, nor healing.
okay, so the wire scale amazon device was too pricy for this project to justify getting, fair enough. But then you guys have this thing at 7:25 ?
Would it be possible for you to make this comparison but using a diamond/sapphire keratome?
i sliced my ankle open while napping obsidian. a chunk launched straight down and cut the flesh on my ankle bone so swiftly i didn’t even realize it happened
Really nice Video and explanation.
What afm tip did you use? Looks like backside Reflex coating, judging by the large sum you get.
I don't think that you're quite done with this one yet. You've probably already heard from someone who's worked in Histology. But, in case you haven't, here's some background.
Some (many) years ago I did such work. Pathology samples are "fixed", embedded in wax blocks, sliced into really delicate slices, these are then floated (and also have the wrinkles flattened out) in a warm water bath. From here, the most promising looking slices are lifted onto a glass slide, dried, dewaxed, stained, and coverslipped. As I recall, we used to cut at around 8 microns. I think that 4 is the absolute limit for steel blades. The blades at that time were like an oversized cut throat razor. they were honed and lapped by machine on a glass plate. These have since been superseded by an oversized analogue of an injector blade, more for convenience than performance. BUT, neither of these provided the best blades. These were made from a special glass bar, which was broken on a machine made for the purpose. With these, slices could be made as thin as one micron. I might add that everything to do with glass knives is too much of a pain in the arse for all but the most fastidious. More blades were thrown away than kept for use. The edges were in every case though, much more even than shown on the obsidian here. This is hardly surprising though. After all, in the one case, you have a regularly shaped object of uniform composition held firmly while very precise pressure is applied. In the other, you belt an irregular lump with a rock.
I suspect that you may have to ring a lot of labs before you find one equipped to make glass blades. But if you do, I reckon that they'd be delighted to supply you with some, once they know what you're about.
Cheers.
The "napped" edges should be serrated in all along the edge in different planes and sometimes in opposing plane. That could be snagging along a wider area then the "ideal" edge.
This video is a rollercoaster of emotions
The tungsten emitter of a scanning electron microscope is a metal point etched down to a single atom at the tip. You literally can't get sharper than that.
5:30 don't know if you caught this, but that is definitely a lathe, and not a mill.
a different method to measure it, pulling each blade across a reference material like the lead, with a fixed static load, maybe even a slight rotation to it to mimic a true slicing motion that these types of blades would be best suited to
there are even devices to make glass blades for cutting samples for transmission electron microscopy. No need for fancy obsidian, only flat glass needed. And you can make finer cuts than with basically anything else except for diamond knives.
I think you've missed an important part, when ancient man cut something with obsidian, he did it in motion, like when you cut something with a knife or a saw, that is, he didn't just touch it, but moved it back and forth like a saw.
Great content as usual. Very interesting for us engineer and machinist types!
Someone really woke up and said
“I’M GONNA SPLIT HAIRS TODAY”
😂
That's the longest "It's not strong enough" I've ever seen.
Now that, is some cutting edge technology.
Perhaps the wire in the sharpness test measured by applied force should be replaced with a softer material such as cotton thread?
This tickles my nerdiness at just the right spot
Das war ein sehr interessantes Video, es war sehr unterhaltsam, macht weiter so!
It’s interesting that obsidian can get that sharp, but it is too brittle and too difficult to get a large uniform edge; i.e. it is impractical for most real-world applications.
i wish this vid were twice as long
I regularly sharpen knives, with a jig, and get extremely consistent results. I have also knapped obsidian, and i will say that occasionally youll produce damn near scary sharp edges of obsidian. Like shave hair and not even feel it sharp, sharper than i can intentionally sharpen knives sharp. They arent the thinnest pieces either, its just the ones that come to a consistent edge.
Well when I was in college we used broken glass to cut sections thinner than a single cell for the electron microscope and since obsidian is glass then yes it probably is one of the sharpest edges possible.
Nice settings! A cutting proces allways involves moving the cutter at the same time putting some pressure on it... Try to cut thick leather with a razoare blade and than compare it with a obsidian blade...
I think that your biggest problem is in fact the strength of the materials. Steel withstands the wire test because it is structurally very strong. Its strength can be adjusted by tempering. That's why they use it for blades! We take it for granted but its a very high tech material. Glass on the other hand despite our 'perception' is a soft material and does not withstand the wire test because the edge deforms under pressure. As would non tempered steel The wire is possibly harder than the glass. If you cut materials that were softer than glass such as mammoth meat you might find that it performed better. (good luck on finding the mammoth meat).