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Water does cut down on dust, but the speed of the sander aerosolizes the water (you're covered in mist within seconds) and those droplets can contain glass (and abrasive) particulates. Wearing a mask with ANY glass cutting/grinding operation is a good idea.

Lol. This video is a joke posted by a clown. Incorrectomundo. Wearing a mask is NOT a 'good idea' it is, in fact, in most civilised countries, a legal requirement (due to the risk of silicosis) including your own. OHSA demands that for indoor or enclosed area processes that create silicate dusts a respirator with an Assigned Protection Factor of at least 10 be worn at all times.

Thanks! I love alternatives. What kind of marker? I haven't found one that will permanently mark silicone caulking. Agreed on the Vaseline! I should use it more often!

@@kentstateglass5011 you can ues any permeant marker as it only needs to stay on long enough to be a cutting guide. im in Australia but if you experiment with markers, ballpoints ect im sure you would find one. or mark the line before your last very thin coat of silicone and the line should just show through.

Yes! But it's tremendously expensive. You can use Fused Silica. This is silica that's been turned from crystaline to amorphous with high heat, but we'd never be able to afford anything bigger than about a golf ball. The good news is simple PPE, good ventilation, and keeping your work station clean will keep you safe. We just had our mold room checked for parts-per-million silica, and it's so safe we could likely be in there w/o masks. Obviously, we ALWAYS use masks. It's likely that a kid playing in a sand box has more exposure to silica dust than we do.

Not a dumb question at all! Powdered glass can be used in mold-making, but it can't replace silica since it melts at the same temp as the glass we're trying to cast. Also, the making of it is extremely time consuming for a few ounces. We're using pounds of material at a time.

We purchase these pipes. There are several manufacturers in the States that make blowpipes for the industry. It is basically just a metal tube, but to withstand the heat for years the tip is made of a special heat-resistant steel.

@kentstateglass5011 I can understand somebody pouring some ugly metal from burning some metal ore few thousand years ago, but getting a pipe or tube outta metal and somehow learning ingredients in nature that would be usable to blow glass.. miracle

There are a number of places, I would do a search online for Pottery Plaster and Silica Flour. If you have a landscaping center nearby you might also find these materials there. You can also order pre-mixed mold material from Ransom & Randolph (www.ransom-randolph.com/glass). They sell a 50/50 Plaster/Silica mix that's comparable in price to buying/mixing yourself.

Glad you liked it!

If you haven't already found it you can watch our video on displacement here: th-cam.com/video/J4V0hcjJaTg/w-d-xo.html

If you're trying to do hot blow-molds the mix would be the same-1:1:1 plaster:silica:water. However, you either need to make your mold more robust (at least 2" thick) or back it up with a layer of chicken wire coated in more mold-mix. This will prevent your mold from splitting apart during the blowing process. If you're trying to make a mold that you can use several times then it's just Plaster, and you blow into it while cold. For the hot blow-mold you want to preheat the mold to at least 1050ºF before you blow into it. That will allow the glass to fill all the detail. Good luck!

@@kentstateglass5011 thank you so much! I’ve made a couple that have already failed already and I will follow this to a T. I think it will work 😊

Also, if you don't belong to Glassies on FB, you should try to get in. Huge community of supportive glass folk that have lots of info. Look up the Labold Method, popularized by James Labold. He has a specific way of layering his molds that works super well. I do a similar method, but make mine a lot thinner and constrain with chicken wire.

Great suggestion!

and if the mold never heated up and still feels cold to the touch a couple hours later if this meand the mold will be subject to cracking in the kiln?

I'm not sure I understand the question. Could you please elaborate? Mostly I don't calculate material volume for hand-build molds like this. If I don't have enough with the first layer, I just mix and add another layer immediately. Actually, multi-layer molds can be stronger than single-layer, so I'm OK if I don't guess right the first time.

Plaster off-gasses at around 1650ºF. At that point it really breaks down as is VERY fragile indeed. What do you need to go to 2000ºF for? Most castings happen at 1450-1600ºF.

@@kentstateglass5011I want to experiment with melting copper between layers of glass. Thats why i need to reach that high of a temperature

There is something called a "Collecting Gather" where you try to "scoop" the glass out of the furnace. This is done by turning faster and sort of skimming along the surface of the glass to push a ball of glass on to the pipe. So, turn faster (and more) and exit the glass at an angle where the glass won't drip back off into the furnace. Hope this helps!

@@kentstateglass5011 Thanks - def makes sense! Will work with that in the hot shop next week

What's not discussed here is the firing schedule. Predrying a mold at about 110-180ºF overnight can help a bit, but mostly molds crack for 4 reasons: 1. Not thick enough. 2" wall thickness is ideal for most castings. 2. Uneven mold thickness. As the mold dries it shrinks. You want this to happen evenly. 3. Too fast up to 1000ºF. This is the "curing" stage of the firing process. About the minimum time is 8 hrs for smaller molds. 4. Racing through the "quartz-inversion" phase. We typically program a 2-3 hr. ramp from 1000-1200ºF to ease the mold material through this point. You can find more info on the curing/firing stage of casting here: th-cam.com/video/BlV_iG1zcZA/w-d-xo.html Hope this helps!

This type of mold doesn't need them. The overlap of the second half acts as keys and locks the two halves together. Hope that helps!

Yes, it's critical that water-based clay is still soft for you to remove it. You can use oil-based clay as well, but it's typically stiffer than the water-based and requires more care removing it. Minimal undercuts are helpful, but you can easily remove any clay that you can reach with a tool. That's actually the advantage of this method: since the clay is soft you don't need to completely avoid undercuts to remove the pattern from the mold.

You are welcome!

Glad it was helpful!

LOL! Love that! Actually, though, there's very little blowing involved in glass blowing. Much, much less effort required than blowing up a balloon.

Some toxins could be in there…

There was someone else around: the camera operator. Because of policy at the time of COVID we both had to wear masks if we were sharing a studio. This was 2020 in the depths of the Pandemic. If you're having trouble understanding enable Closed Captioning. It's pretty accurate! Hope this helps.

​@@kentstateglass5011You don't have to explain yourself to morons, my friend.

Glad it helped!

No Part 2 yet. This video just covers loading the kiln. Would you like to see a video of some parts of the casting process?

Glad it was helpful!

Agree! This was made during the pandemic when we were required to wear masks in all rooms. Also, I'm working with silica flour, so an N95 is an important safety measure. The good news is the Closed Captioning (CC) is pretty good on this. Enable that and it should help!

Good idea! Thankfully there are redundant safety systems on our kilns. There is the safety switch which kills power at the controller and is designed to fail safe. There is also the fact that the kiln is in OFF mode when we are loading the kiln. Finally, there is fuse/breaker box on the kiln as a 100% safety measure. On our kilns that are plugged into an outlet, we can also unplug them to be even more sure. (I always do this when servicing those kilns.)

Glad it was helpful!

Sorry for the delayed reply. YES! You can absolutely used water to wash clay off the inside of your mold... if you're using water-based clay. For oil-based clay I recommend using a mold release and then compressed air to blow the clay particles off the surface.

If you're referring to the moment when it's still on the blowpipe, I'm straightening the neckline so it's in line with the blowpipe. That helps the body of the cup be on center.