Hydrocal Hell

Use this forum for discussion on kiln casting, pate de verre, and related topics.

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Kathleen Ash
Posts: 1
Joined: Mon Jul 05, 2021 9:19 pm

Hydrocal Hell

Post by Kathleen Ash »

Hello, I have not been able to find an answer and I'm hoping the forum can help: I am in the process of making a pate de verre box. The folks at Bullseye said that I would be able to use straight Hydrocal for my plaster mold. In Boyce Lundstrom's book he said to take the mold to 1200 degrees to burn out the wax that was left after steaming. The lid of my push mold ended up with edge cracking and the bowl part of the mold had several hairline cracks. I patched them up, wired the circumference and am hoping for the best. The test box looks pretty good in the kiln, but it's still at 1000. So my question is two part: Do I have to mix in silica flour with Hydrocal to prevent cracking? Is it OK to leave a waxy film on the inside of the mold and avoid firing the mold pre-filling? Thanks in advance! Kathleen
Steph Mader
Posts: 59
Joined: Tue Mar 11, 2003 1:45 am
Location: Freeland, WA

Re: Hydrocal Hell

Post by Steph Mader »

Hi Kathleen,
Yes, mix at least 50% silica flour with the hydrocal to make casting investment. It helps to add some chopped fiberglass too, to help hold everything together. Hydrocal by iteself can't handle the heat of the kiln and will break down and fail. Good luck!
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