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Mold Blisters - Lost Wax Kiln Cast

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

Mold Blisters - Lost Wax Kiln Cast

Postby cemoore » Sun Sep 04, 2016 8:21 am

Hi All,

I seem to get soft blisters/bubbles/distentions - not sure what to call them - in my mold face. They arise during steaming and I'm not sure why. In the last mold where this happened, I used two splash coats and a jacket coat, but I'm not necessarily seeing a pattern as I've seen it before with other layer configurations (e.g., one splash coat, one jacket coat) and different investment formulas, usually based on a 50/50 plaster/silica plus maybe some minor amount of EPK to help release and surface smoothness. If I push on one when mold still warm and moist from steam, it will flatten out but then leaves a rough edge or break on the mold face.

Could it be I'm creating a gap of some sort between layers trapping air that I"m not seeing when laying up the coats? If the gap is close enough to the the mold face, that is the 1st layer was fairly thin and fragile, maybe the steam is distorting it?

PS, I put this same question to the warmglass.com board just now.

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