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devit issues - need help

For discussion of processes related to using Bullseye glass, including kilnforming and kilncasting, torchwork, blowing and stained glass.

Re: devit issues - need help

Postby jestersbaubles » Thu Apr 18, 2019 7:28 pm

Air drying is typically not sufficient for plaster molds. You need to fire them in the kiln before using.

Bullseye has some excellent video tutorials on open-face casting that provides the details.

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Dana Worley Fused Glass Designs
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Re: devit issues - need help

Postby jagboy69 » Fri Apr 19, 2019 1:43 am

I'm firing bandust 101 at about 350f for 3-4 hours. Nice and slow. That mixture does contain plaster of paris and needs the bound water driven out to prevent cracking. The silica in it allows the plaster to tolerate the high temperatures. I believe the plaster is just the binder. Some metal casters use 50/50 sand and PoP. It makes a lousy investment material for molten aluminum or bronze and can be dangerous. I have zero issues with spending a few bucks for proper materials.. 8-)
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Re: devit issues - need help

Postby library » Sat Apr 20, 2019 1:36 pm


Do you have a firing schedule for molds? I'm worried about doing this because i usually get minor cracks in my mold when firing partially dry with the glass in. Also you mentioned a mold dryer...what does this consist of?


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Re: devit issues - need help

Postby jagboy69 » Sat Apr 27, 2019 12:15 am

Hey I might have found something that could help you and I out.

I just came across an investment called mold mix 6. They claim free of haze! It is not your typical cheap plaster/silica flour mix. This one is alumina fibers and alumina powders and even capable of tolerating bronze. It is not cheap, but neither is my time! I'm trying bandust one more time with Gaffer glass and if this doesn't work, I'm chucking that 50lb box of investment in the TRASH!

If anyone has any thoughts about mold mix, I'd be thankful if you could share your experience with this stuff. Thanks!
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Re: devit issues - need help

Postby marykaynitchie » Tue Apr 30, 2019 4:18 pm

Here are some free articles that explain how we do lost wax and one kind of open-faced castings in Bullseye studios:
TipSheet 5: Bullseye Box Casting
http://www.bullseyeglass.com/methods-id ... sting.html
TipSheet 8: Basic Lost Wax Kilncasting
http://www.bullseyeglass.com/methods-id ... sting.html

For an annual subscription fee (currently $45 per year) you can have access to over 100 videos including some on kilncasting:

Topic: Kilncasting:
https://videos.bullseyeglass.com/video- ... lncasting/

It's true that plaster-silica mold require prefiring to drive out bound water.
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Bullseye Glass Co.

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