Digital casting: 3D printed molds for concrete and plaster!
ฝัง
- เผยแพร่เมื่อ 9 ธ.ค. 2018
- 3D Printing is really good at making light plastic parts. Here's how I made heavy concrete and plaster parts from my prints instead!
Filament used: Aprintapro Flex Hard go.toms3d.org/AProFlexHard
Product links are affiliate links - I may earn a commission on qualifying purchases (at no extra cost to you)
🎥 All my video gear toms3d.org/my-gear
I use Epidemic Sound, sign up for a 30-day free trial here share.epidemicsound.com/MadeWi...
🎧 Check out the Meltzone Podcast (with CNC Kitchen)! / @themeltzone
👐 Enjoying the videos? Support my work on Patreon! / toms3dp - วิทยาศาสตร์และเทคโนโลยี
Hi Tom, love your channel and refer to it all the time in regards to 3D Printing. As for casting 3D molds and models, I do a ton of this in my shop and have done so for 3-4 years now. I mostly produce ceramic molds for production and I believe I can help improve on your castings. For the concrete, it simply needed more time and honestly so did the plaster, both cure not by evaporation but through a chemical reaction that produces heat. The best time I have found for demolding is just after the heat has started to dissipate. I personally prefer not to speed the "drying" of a fresh green mold made from plaster and prefer to let it dry naturally, for some reason I find it weakens the casting. I also prefer to let it dry naturally 3 days to a week. Plaster is also not the ideal material to pain unless it is dried thoroughly and sealed with a clear coat as it will continue to absorb moisture over time as that is what it is really good at. More importantly, lets discuss the casting method. You should look up mold soap if casting in plaster, this works way better than dish soap, oil or petroleum jelly. These all will work but mold soap will do the job much better and not leave problematic residues. In a pinch I use oil soaps for cleaning wood, in the states one can use Murphy's oil but mold soap works better. There are plenty of release agents and concrete has its own release agents but you need one for a clean casting. The air bubbles you got on the plaster casting can be eliminated. Plaster is an incredibly hi-resolution material if mixed properly, you also need to use casting plaster as opposed to "plaster of paris" and the craft - art store plasters, you can also use hydrocal, a cement/plaster combo, much harder and great to work with. Look up mixing plaster for mold making, I could tell by your pour something is off in the process you use, it was a bit on the thick side and the lumps were a bit worry some. The hammer vibration technique you used was spot on. Those are the big things, if you need further support please reach out on more private lines and we can discuss. Good luck.
how dp you cast 1, 2, and 4 dimensional molds, as opposed to the 3d molds?
NiceWhenEarned RudeMostlyElse Hi there, I am not sure what you mean by this question? All molds are to varying degrees three dimensional and I think you might mean single part, as per Tom’s example here to two part, three part and on to many part molds. If so, this is a matter of blocking and dating the section you want to cast and going from there.
I agree, both needed more cure time.
@@nicewhenearnedrudemostlyel489 4 dimensional molds? Do you mean all sides casted? That is still considered a 3d casting, and the most popular way to cast that is either using lost wax, or a flexible rubber mold in 2 or more segments. Realy depends upon your finished product.
thank you for sharing your experience! makes my search a lot easier
Look up the term "Release Agent". That will help. Also, if you have a palm sander turn it on and put it against the edge of the mold. That will vibrate the bubbles to the top.
well, even a very thin coat of WD40 might do the trick as well. or any other oil base for that matter
@@enricotempert "Release Agent"...doesn't matter what it is. Corn Starch, Talc, etc is used quite a bit for metal casting release agents...For concrete counter tops many have used a thin layer of petroleum jelly.
Yes the eccentric sander was the first thing that came to my mind too.. vacuum would be much better, but I guess it`s harder to get one, and it`s more expensive
@@WreckDiver99 for concrete or cement, a powder wouldn't work that well. of course, better than nothing at all, but in construction an oil base is almost always used. and yes. petroleum jelly is oil based. although I think it is a bit too thick for this little thing. it will leave marks if not spread very thinly
@@enricotempert No doubt on the powders...I was just giving an example of a "release agent". Many people hear that word and immediately think that means some ultra special item. Sure there are "Parting Powders" available for casting operations, but talc works great. For Concrete I've used PAM Cooking Spray (WORKS AWESOME), as well as Petroleum Jelly, and even "AquaCon" (which is actually a "commerical" release agent).
Definitely with this filaflex you can make excellent molds.
Small tricks to improve casting in molds of concrete, gypsum or plaster of Paris objects:
with each new casting, brush the surfaces of the mold with liquid soap: the one for dishes is fine, this will facilitate the detachment of the surfaces,
the most technologic will be able to use professional release agents, but to make tests the soap is excellent, I used it at middle school in the hours of art.
To avoid air inclusions there are two methods: prepare a small amount of more liquid dough and pour it into the mold covering all the surface that will be visible, stirring and beating the mold as Thomas did, let it harden a little and then fill with the rest of the dough with a normal consistency.
Second method, more complicated, put the mold filled in a vacuum chamber that will remove all the air, vibrate the mixture and re-inject air before it solidifies: the atmospheric pressure returning will further compress the mixture, reducing the number and size of the bubbles .
Third and last trick: a lot of patience: fill the mold, put it aside and forget it for a couple of days at a minimum.
Another little help in making molds: vertical surfaces should become slightly oblique: slightly conical the cylinders and slightly pyramidal the prisms.
bye
I'd do plaster and I'd also reinforce it with some kind of fibre (Cotton - like a cast for a broken arm, glass also works, carbon too. Even hair if you want to go oldfashioned.) It'll help protect against some of the brittleness which leads to cracking.
Hi Tom, an advice about plaster in case you get to read this : we do that for a living, there is plaster with additives that make it a lot stronger, better paint adhesion etc, look up for it, or pm in case you want some more info. Nice video btw, keep going !
Hi Tom. I use 3parts fine sand, 2 parts rough agregate like fine gravel 3-4mm and one part cement. I get awesome castings like this. Remember to vibrate it heavily to get the bubbles out.
I printed a relief map of my region (using USGS data) in good old PLA, made a plaster cast of that (using "PAM" as a release), and used that to make multiple ceramic slip castings. The layer lines and surface details carried over perfectly to the fired pieces. I'm working on the metallic glazes now...
Great project, the results looked superb.
Im glad you mentioned printing the flexibles at 0.2 layer height I was having a problem printing a part for my quadcopter and changing the layer height nailed it. Danke!
That is so cool, Tom! Thanks for sharing! You've made it look so simple I feel like trying!
I am curious to see what effect the different infill patterns and percentages will have on the top surface of the print, and therefore the mould. The gyroid waves looked very pretty on the top of the candle-holder with the shadows that it casts on itself at 14:28! :)
Good video. Exploring 3D printed molds, learning a lot. Loving the process.
Couple things I learned from a master modeler making plaster molds for latex masks (that I bet others have already commented on, oh well):
If you want the plaster to last (say, if you want to use it to cast latex), add some kind of fibrous material. We used burlap in the mask making class which works fantastically, but I bet gauze or fiberglass would strengthen it as well (well, all right, I just tossed the gauze and fiberglass out there because I've always wanted to see how the plaster would behave with them).
If you want to reduce the bubbles on the surface, slowly pour a thin slurry of plaster (consistency of crepe batter if memory serves) on the surface of the master. If you've ever seen pastry chefs pour ganache on a cake, it's the same principle. It will run off, so you'll need to scoop it up and pour it back over the top until it thickens. Then you layer plaster-soaked fabric onto this initial shell to reinforce it.
With plaster you can make also molds to pour molten aluminium. That's a cool project. Unfortunately I do not have a place for such experiments
I really like the 60fps video you shoot, gives a nice look to the overall content, and the lighting is excellent! This is a cool project, I've been thinking of printing then making silicone molds to cast resin in.
From a civil engineer's point of view this video and the comments are just awesome. Thanks for that.
I have printed a mold of a Buddha head and cast it with concrete. I chose to make the mold one time use so I printed it in PLA. No wooden parts. I used fine concrete and could see layer lines from the print very well. After a few days I started peeling the PLA. Worked very good.
With the concrete I had fewer breakages and chippings than with the plaster, when casting a chess set as part of a university project. I ran test casts using plaster (Herculite, a strong plaster used for architectural models) before making a few sets in plaster as well as concrete.
I used a mould release agent (any oil will work, I've used petroleum jelly, vegetable oil, olive oil, sunflower oil in the past as well as industrial concrete release agent for this project) on all castings.
As far as the angle goes, it will definitely help in terms of releasing of there's a 2-5° taper.
I had difficulty in releasing certain pieces, so for the next iteration I plan to add a small hole that would be plugged for the cast, with a larger concentric divet to allow me to blow the castings out of the moulds with compressed air. It's possible that the taper may not be required with this change.
If you are going to use concrete it would be a good idea to coat the mould and the pattern with a light oil or grease. Makes easier to seperate
Hello Tom, Thank you for making a video about printed molds. Its is something I am looking into myself. First off, your videos have been extremely helpful to me in learning 3D printing. Perhaps as a way to pay you back I'd like to help you in your mold making venture. I have experience in making many different types of molds for everything from vacuum bagged carbon fiber to bronze sculptures. Here are a few things you might find helpful.
1. IMO the best release is wax such as the type used for wood floors. Rub it back with a cloth once dry. This will get a truly smooth finish. All the other mentioned releases work; petroleum jelly, talc, dish soap, vegetable shortening, etc. but each type leaves micro swirls or bubbles on the casts surface.
2. When mixing plaster do so by hand. Add the plaster to cold water, mix slowly and let it work through your fingers. This will help reduce bubbles. As mentioned below, vibration from a sander can help remaining bubbles surface.
3. Once cured, seal your plaster with shellac before painting. Its the only thing I know of that bonds to plaster. Polyurethane DOES NOT. It will try and trick you for a few days before it delaminates!!!
4. A good high-strength, low-weight alternative to plaster is hydrocal.
I hope this helps. Keep up the great work and thanks again for all of the help you have provided me in the past!
To remove the bubbles, try putting the mold in a plastic bag and use a shop vac to produce some vacuum while hammering. Since the vacuum makes the air in the infill expand it is necessary to remove the vacuum after removing the bubbles.
There's a product I've used in the past for making outdoor stepping stones with stained glass tops. It's called white mosaic outdoor cement and is made by a few different manufacturers. I tried to find material specs, but all I could find that it was portland cement and sand. I agree on keeping the draft angles, and vaseline makes a good mold release agent. Thanks for another great video!
If you have a hand sander, you can turn it on and put it up against the side of the mold after you pour the plaster or concrete into it to help vibrate the bubbles out. That can work a bit better than hammering the table the form is attached to.
Add a very thin layer of petroleum jelly on the inside of the wodden frame. That will help removing it. That second attempt came out much better. Please use plaster. Just add some gravel or course sand. You could build a vibrator that would help getting rid of the voids ;-)
I've seen other TH-camrs use melamine forms for making things like counter tops and tables, and there are some ideas you could take from those videos.
Just a high-level overview of some of them:
- Use glass fibers in the concrete mix to give it some tensile strength. It will hold together better, and will be far less likely to be breakable by hand.
- Apply a simple paste wax to the corners and edges, then seal them with a silicone sealant. Then, skim over the silicone with something that has a rounded edge (I've seen some use a cake fondant ball tool to accomplish this), to push the silicone into the corners, and separate the edges of the silicone from the corner. Then, once the silicone cures, peel off the separated edge, leaving the corners in place. This helps seal against leaks, and softens the sharper edges of the concrete. It also helps with releasing later on.
- For the detailed mold, apply a light layer of a releasing agent. I've seen commercial applications use things like linseed oil, but there is also a synthetic product intended for this. It'll make pulling the mold out much easier and cleaner.
- Some people have already mentioned vibrating your concrete when finished, but it's almost unavoidable that you'll need to make a bit of a slurry mix to fill pits and imperfections, and then sand that down when done.
Good addition of the draft, but the sharp corners at the base of the model can cause major headaches as well. Typically in metalcasting we use some level of chamfer or radius on inside corners like that for better mold release.
I would love to see whether or how much can the concrete hide imperfections from 3D printing. Will the layer lines show through? Could you do a mold printed with a big nozzle and fat layers?
If you use shellac as a primer you can apply 2-3 medium weight layers in an hour and it won't react with the plaster at all. You can paint over the shellack with all types of paint after drying it for an hour in the oven.
Tips from a painter:
Tip#1: to avoid paint bleeding use the correct tape for what your doing. For example I use tape from 3m so blue painters tape has a low strength adhesive. It generally goes like that Blue, green, orange, and light green for terms of adhesive strength for 3m atleast. In the case of concrete use light green.
Tip#2: when tapping surfaces dont lay down the tape while pulling on it tight. Pull some off the roll and let it hang loose and push it down while its loose in your other hand. This way its properly secured to what your painting so there is no bleeding. This works super well on textured walls/surfaces and it has never failed me so I always end up with clean straight lines
I would suggest using using Hydrostone, it falls in between plaster and concrete in hardness and doesn't have all the gravel like concrete. Basically it will have the same smooth texture as plaster but be much stronger.
We used to do precast concrete blocks when I was a kid & the release agent we used with the concrete was old engine oil. I'm sure others here will have many reasons why it can't / shouldn't be used but it's what we did & the building that the blocks were used in is still standing.
Hi Tom, awesome use of 3D printing. I'd try dusting the print and the inside of the frame with talcum powder, it will act as a release agent. Cover the faces to be cast then tip out the excess. I'd also use a random orbital sander on the top of the wooden frame for about 120 secs after you do the pour. This will work much better than your awesome hammer technique (remove the abrasive pad from the sander, of course). having a release agent should make it easier to use concrete too. For concrete I'd leave it to harden for a couple of days, in a warm place, your attempt looked like it was still quite damp inside. Good luck with your next try. Looking forward to seeing how it goes.
Water based paint like latex acrylic makes more sense with plaster, whatever you would put on your plaster wall. Also, like concrete, plaster is made by applying heat to drive off moisture, so heat can change the structure of the plaster.
You can seal cement (and probably plaster as well) by painting on a coat of sodium silicate. This gives you a thin glass coating that will soak into the porous material and create a smooth, glossy surface. If you don't mind that kind of surface, it would solve some of the problems with painting.
It's great to see you making things again. I might even have a go at one of these myself ;-)
I'm casting plaster candlesticks in a multi-part 3D printed mould. Printing flexible as slowly as 20mm/sec helps a lot with the quality. Using Prusa Slicer 'Variable Layer Height' option saves a lot of print time. (Prusa Slicer also works with non Prusa 3D printers)
When your painting fresh plaster you need to do a 'wet coat'. It's super easy you just need to the mix the paint with water (1:1 ratio), then paint over again with pure paint when its dry.
I'm making slip cast pottery with plaster moulds. The patterns I design in Fusion 360. I print these, then make moulds off of them. I also CAD and print part line guides to help with complex moulds. When I get a site together, I'll publish pictures of my results.
If the the positive (3d print) is going to be used just a few times, try using a sandable primer thinly applied before casting. It can smooth out the print lines considerably.
Anchoring cement will also make a very hard cement product (but heavy). Add some fine aggregate or tiny glass beads and maybe a bit of concrete colorant for a more finished appearance.
Naturally, I think we can all agree you need to do both plaster and concrete and see what turns out better.
Was find mould printed in TPU? About to do something similar go this and wondering if I should be getting myself a flexible filament for the project!
Do you make any of your printing profiles available for others? I'm still trying to dial in Nylon and TPU profiles.
Would dissolvable pla be a possibility to create complex molds ?
Or will this degrade due to the moisture in the cement ?
depends on your end results you want. water putty is a lot like plaster but harder. brush the mold first after waxing. the bad thing about wax is when you want to paint . dont use spray primer but use PVA which is for drywall. if you want to make it lighter you can use pearlite in the mix. someone suggested using some sort of fiber material. you can use even chicken wire to help. or just get some fiber sheet and pour some do the hammer thing to level. lay some fiber pour some more hammer then add some more . id do a couple layers and cross the fibers.
oh and dont discount something like bondo
The increased shrinkage of Plaster is a good and a bad thing. Initial release from your 3D plug will be easier. That same shrinkage can cause cracking and other issues so watch your larger parts. Easier sanding, filing etc over concrete is a plus. Look at some Concrete Benchtop videos for ideas on the concrete alternative. Good video as always :)
You can purchase "concrete fibres" in various sizes to reinforce concrete or plaster. They are just small strands of polypropylene that help bind the material. You'll need to mix them in really well.
I've been going back and forth on getting fibers to try. Some sources say it really only helps in GFRC blends (which are not easily sourced here without paying $50 shipping to have a $30 bag sent to you), whereas in regular blends it really doesn't help that much because the concrete itself doesn't have the properties to transfer the load to the various fibers without the added polymers of a GFRC blend.
as mentioned in the comments before, a releasing agent, like for example WD40 will do the trick. but also no 90 degree inward angles, cause that is where the mortar gets stuck in
I got also quite results with Vaseline as a releasing agent.
Nice Channel! You do a great job, thanks!
Cement based mortar is meant to be soft ..... if it is too strong then the bricks crack :) - but then you did say you knew it was the wrong thing. Paint over the surface with a slurry of cement first to help eliminate more of the bubbles. Yes vibrate. Use a plasticiser rather than more water. But water is important to the curing - so good to cover like you did. Like the idea of the skin and plug - though TPU is hard to get the support material out. Love to see these experiments!
Do you answer questions? I just had to put my 13 year old dog down and we had his paw print done (plastered) can it be done this way? A 3D mold version of it?
you need a sander or something to shake the table to get the bubbles out. also in the US there's this really fine concrete called quikrete that is used for countertops and stuff and can be smooth as glass. maybe you can find something in Germany that's similar.
I would assume the plaster would break down quickly given how water soluble it is. At least the surface from being handled. If it were me I would print the mold from PLA, hit it with a media blaster to smooth out the part, add the walls to the mold and seal with silicone, Spray everything with clear coat pre poor, poor REALLY thin concrete in, use something to vibrate it like a palm sander (really anything that spins fast and can be rigged off balance will work like a drill with a large hex key in the chuck). The PLA mold can be shrunk/melted away with a heat gun once the concrete has cured.
Should come out perfect.
Hi, Thomas! What to do with those bubbles on edges (of plaster)? I've thought you'll heal them before baking... Oh, I've thought it will be a form to make some "molds" (to clone the initial form)!
IMO concrete is superior if you want to make some permanent outdoor shells. You can even make some small metal roofs for these molds so the candles will be protected from rain.
The plaster part did not dry out completely. That is why you've got these flakes and wrinkles when you've applied the organic solvent based primer on it
Haven't seen thomas this enthusiastic before 😂
Great content as always !
I would add munched fibreglass strands into the mix. That will help keep the cracking and splitting down.
Second the release agent. I will occasionally use the wax ones so I can merely heat the mould and it falls out.
Or, if you are making a bunch of these things, I'd make a silicon mould and then no release agent is rarely required.
your videos are always beautiful
Suggestions:
1) add 10% PVA glue to mortar mix. 2) sprinkle talcum powder over mold. 3)vibrate to remove bubbles 4)cover in polythene and leave for at least a week....it’s a chemical reaction that needs water....not drying!
I'd recommend for this size of casting always using quick dry cement, I also mix in about 5% wood glue (not craft pva as i think its got something in it thats not good for concrete) as I dont want to use fibre strengthening on thin casts and it adds another level of sealant. & mold release is always a good idea.
Hi Thomas, nice Video! Normal plaster can be a little bit brittle. There is a plaster type called Stewalin which is more robust. If you want to paint the whole thing, maybe it is better to coloring the pouring mixture. The advantage of this is if a part chips off, there is no white spot.
A tip use quick set concrete and vibrate with an orbital sander on the bench it'll cause it to make a beautiful product
If you have a vibrating sander (the rectangle once) you might get rid of the last bubbles. Just run it on the table instead of hammering.
For the sign, you can cast it in an epoxy sand/stone mix. It will be many times stronger than concrete and harden overnight. The mix should be like moist sand, ie. quite dry. Using different colors of sand in the mix will produce different looks if you leave it untreated.
Don't forget to wax the mold with a release agent when casting epoxy.
If it's not too heavy, could you put the mold on a moving printer bed and make the bed move at short distances (vibrate), backward and forwards, to to remove the bubbles? And if you have a printer enclosure, heat the bed to dry the mold. Just seems like a nice way of using 3D printers!!
Which plaster u used and how long did it need to cure?
Definitely try concrete again. I browsed a lot of comments and didn’t see Paste Wax recommended. Many release agents can leave behind residue or an undesirable look. Paste Wax doesn’t seem to have that problem.
Thxs for ur video where xan i get flexible filament component??
Love your videos and your ideas. There is something I need to know. I have looked all over and can't find those screwdriver style Allen wrenches. Where to go please.
I got a perfect gift idea for my dad now....
only reason to use a flexible is you either want no draft on the part or have details with undercuts...if its something simple were a slight draft angle is ok you prob want to go with just simple filament that can be smoothed(making release of the mold even easier)...that being said you may like the textures left from the printer.Either way it turned out well and if you are going to make a larger piece you may want to look into making foamed concrete...much lighter...far stronger then plaster but will reguire its own amount of experimentation to get right lol
OMG - that was the MPCNC you're printing in the file meny. How's it going?
Frohe Weihnachten!
Also, to reduce bubbles, try painting the inside of the mold with "wet water". Basically water with less surface tension. Use a surfactant. Google hirst arts for info on casting plaster.
May want to consider gold (fake gold) leaf. Super inexpensive, easy to apply, little masking needed for something like that and of course a much warmer texture and appearance. They also have copper and silver leafs that are really nice. Adhesive for the leaf would require no priming.
Concrete is a great medium. No more difficult than the plaster and usually much less expensive then say plaster of Paris.
There is a product called Merlin's magic and excalibur that is used for mold making. It has the strength of concrete but the workability of plaster. You can use waterdowned jet dry to help with the bubbles
If you like a textured look, you might try using Cura's "Fuzzy Skin" option when you print the mold. The height and density of the texture is controllable.
I'm afraid that would lock the printed inserts solidly into the cast. Maybe once I've really figured this thing out, I can start playing with some of the crazier options!
Nice Idea
Couple things : use a release agent like Pam (cooking spray) or paste wax. You can use mortar, but you probably need to reinforce it with glass or basalt fibers.
Add a sprinkle of wallpaper adhesive to your plaster; it will make it less brittle.
If you need higher strength than plaster the dental industry has a good formulation. "Dental Plaster" is strong stuff
What brand sweatshirts are you wearing in this video?
13:05 Shoutout to OG Belton Montana! keep than can it's an artifact of the great Graffiti days.
candle holder, what good is that? but good info
Plaster is only fully cured when it cools down. Until then, no painting unless you're using watercolors (effectively making it a fresco). As for the 3D printed mold, i'd add at least a chamfer, maybe even a fillet to the corners. Also, petroleum jelly should make demolding easier.
Has anyone mentioned covering the plaster with PVA before painting it ?
I have had great results with small concrete items using a wetting agent which allows you to use more water, this provided greater detail and strength, but alas, longer cure times.
Great job. My vote is for concrete. It has more of an industrial feel and look to it.
For more complex shapes, you could probably just print the mold in PLA, and then once the plaster/concrete is dry, put it in an oven at high temperature to melt out the plastic. You just have to be very careful and slowly increase the temperature, so the remaining moisture can get out without turning to steam an cracking the plaster/concrete.
Hello! I like your projects and your interviews! :) Are the walls for the molds
perpendicular to the base? If yes than its really came out good! :)
Some release agent would go a long way.
Also if you hit it with clear coat after taping it off, you can prevent the bleed.
Release agents will soak into the cement, concrete or plaster and will ruin a latter painting. Just leave it dry more time. Plaster should be creamy to mold pieces, it will make much better parts but also can hold bubbles. Once it is dry, if you are going to paint it, you need to apply a sealant, but not regular wood primers. You can try some diluted latex or pva glue if you do not find specific sealants for walls. Ah, and one more thing, plaster becomes hot when curing, as you already noticed, so my advice is pour a test on a disposable container and find out how hot it goes. 3dprinted plastics may distort.
I'm curing my concrete pieces at least 7 days underwater, after 24 hours on the mold, if the centerpiece doesn't unmold it will after some days underwater.
My recipe is 3 parts fine sand and 2 parts grey cement.
What's the model of clamp and the bosch tool?
If you don't have any melamine faced chipboard, you could always use parcel tape as an option to line your box.
seal the corners of your mold box with silicone to prevent moisture wicking to prevent the corners from breaking as easily.
can I have a link of the cutting tool at 3.16 ?
take a hand sander and put it up against the sides while the plaster is still wet to remove more of the air bubbles
Deutschland oder Österreich?
Das Infinity Blue ist echt gut.
Hast du schon das Flexible Filament von DasFilament getestet?
Spray your mold with a LIGHT coating of cooking oil. That will help it comeout easier. To get rid of the 'bug holes', make the concret/plaster a bit more liquidy.
Love how you "covered" up the saws brand with blue tape... ;)