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Castalot Issues

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Castalot Issues

Postby beachwalkerboxes » Sat Jun 21, 2014 12:28 pm

Anybody with any significant experience with castalot? I'm trying to make reusable molds of a box shape, and the glass is always glued tight to the castalot after firing, making it more like cost-a -lot. I have kiln-washed the dickens out of it, prefired it according to directions, it's a plain box with no undercuts. I think the total lack of draft due to the steep sides is a problem, and I think the melting glass may be washing my kiln wash down those steep sides. Also, the contraction of the glass around the inside part of the box mold may be pinching it so tightly that I can't get the glass to release. The firing schedule is working- I get a glass box- but I have to break the mold to get it out. I contacted Michael Dupille, the inventer, and he suggested a different method of kiln washing and a different firing schedule, but it made no difference.

If anyone has any ideas for how to make this work better, or a different reusable mold material, please let me know! For now I'm trying a box with much shallower sides and a round shape instead of square, so maybe that will work, but I still think the pinching of the inside part of the mold will be an issue.

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Re: Castalot Issues

Postby Twin Vision Glass » Sun Jun 22, 2014 6:47 pm

Make the inside of the mold hollow .(backing with sand) Then when the glass shrinks it will not pinch so much. The inside of the mold has to be thin enough to give the glass the availability to shrink. Perhaps you can configure a mold that is two parts and replace inside each time. But re-usable molds for boxes are very tricky. Cynthia Morgan is a glass artist who has conquered many a problem and hopefully she will chime in. Les
Leslie Rowe-Israelson
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Twin Vision Glass
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Re: Castalot Issues

Postby wrziegler5 » Thu Jun 26, 2014 5:39 pm

I think Leslie just nailed it.
If I was attempting to go where you are attempting to go; I would make a positive mold of the inside of my box with a beveled bottom (sufficient enough to use as a base for the entire mold once it is completely assembled.) Then I would make a negative mold of that; of a material sufficiently strong to stand up to many castings (cold). Once that step was complete I would make a positive of foundry sand with a binding agent. This would form the inside of my box and with the bevel, a base which would not be porous at casting temperatures.

After this , a two piece mold of the exterior of my box (I have not used Cast-A-Lot, I assume it is reused after a casting) this mold would need to be tight to prevent heavy flashing. I believe I would do the entire mold round so I could wrap thin stainless steel around the exterior to hold it all together along with stainless steel hose clamps.

Place in Kiln, run firing schedule, de-mold (this is where the foundry sand comes in handy) and assess my results.

Once again, I hope I sufficiently understand the problem and you find something here useful.

Best Regards,


New to glass but not the foundry.
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Re: Castalot Issues

Postby glassdreams » Thu Oct 04, 2018 8:18 pm

Can you possibly submit pictures of what you are describing as a problem with Castalot? or something similar so I can get a visual idea?
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