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Lost Wax Kilncasting

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Lost Wax Kilncasting

Postby Chris_Petrauskas » Mon Jan 19, 2015 2:50 pm

Watch the Lesson at:

Please discuss and comment in this thread.

Chris Petrauskas
Bullseye Glass Co.
Portland, Oregon, USA
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Re: Lost Wax Kilncasting

Postby eegee.j » Thu Apr 06, 2017 9:04 am

I know this thread is old, but I'm trying to figure out the math in calculating the amount of investment needed. In both this video lesson (and in TipSheet 5 & 8), the volume of the surrounding box is calculated and then divided by 2 and multiplied by 0.64.

Where do the magic numbers 2 and 0.64 come from? ie - how was this equation determined to calculate the amount of investment from the model volume? Any direction here is very appreciated.

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Re: Lost Wax Kilncasting

Postby Ted » Tue Apr 11, 2017 8:49 am

Hello Eric,

This is based on our experience handbuilding multi-layered molds for this size of object. We found that if we used the full volume of space that the objects occupy, we had about twice the investment that we needed.

The multiplier of .64 for the water weight in metric units works for investments mixed at a ratio of 1 water:1.75 investment as well as investments mixed at 1 water:2 investment. In the latter formula you will have more total material. The .64 multiplier originated in technical materials provided by US Gypsum (USG). They are the manufacturer of the plaster used in the investment.

If you want to do this same thing using imperial measurements (cubic inches), use a multiplier of .023 for the water weight in pounds.

I hope that this is helpful.

Thank you,

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Re: Lost Wax Kilncasting

Postby eegee.j » Fri Apr 14, 2017 9:57 am

Thanks Ted. I was also able to arrive at that .64 constant by measuring the specific gravity of the wet investment mix. It turns out that Brenda Griffith does a similar calculation in her book "Kiln Formed Glass - Beyond the Basics". So it all makes sense now :D
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