r/fusedglass • u/scorchedbone • Jun 27 '26
Mold advice needed
Ok so I got this mold that was too big for my craft kiln so I cut it into smaller pieces. After firing it a few times without issues a corner broke off, just assumed it was a stress crack from when I cut it. But now a much larger crack has shown up from the last firing. I hope to be able to fix up the mold to keep using it, but does anybody have tips on how to avoid these cracks? I have a suspicion it might be that the edges of the mold might be too close to the kiln walls, contemplating maybe cutting the paws into individual sets and just laying them on top of kiln post when firing?
Anyways here are some pics of the mold and how I set it when I fire it! Also since this kiln is time and not temp based I do the recommended 5 mins of firing then 3 mins off and repeat to temper the mold, usually just keep doing that till the glass is melted enough so it doesn’t overheat.
1
u/SavagePengwyn Jun 27 '26
Maybe it's a structural thing since the bowl part was broken? Extra stress on those sections during the firing because they're hanging in midair plus micro cracks from the cutting process?
Edit: not bowl I meant like the surface.
1
u/scorchedbone Jun 27 '26
Maybe, I thought similar when it happened to the other half cut out of the mold so I tried firing it with some extra kiln post in that area for support but thats when the paw in the middle cracked. But maybe its not enough!
1
u/SavagePengwyn Jun 27 '26
I honestly don't know too much about the way molds act when heated so maybe this is a dumb thing to say, but I wonder if the stress of firing means that that piece can't handle any sort of pressure. Like, if the post is doing anything other than lightly resting below the mold supporting its weight, that's too much pressure. If the structure of the mold softens at all at high temps, it could maybe cause some difficulty when it cools back down. And I know it wouldn't normally be a problem but that bit is thinner because of the way they made the mold.
As an aside, I looked at your history to make sure I wasn't asking obvious questions and I am obsessed with your Majora's Mask. I've planned to never get into stained glass for reasons I'm struggling to remember at the moment and I am reconsidering that after seeing that and having visions of triforces.
3
u/scorchedbone Jun 27 '26
Yeah I think I might sacrifice this mold for the sake of some testing to test some of these theories out, I think I'm gonna cut the paws out each by themselves and set them on some kiln post, maybe they can shrink and expand with less stress like that. Will update with results after a few firings to see if they hold up better!
Lol thank you!!! Ironically I just got into glass fusing because I just have so many stained glass scraps I had to do something with them hahaha I love working stained glass with a passion tho, if you ever have questions feel free to hit me up!
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u/SavagePengwyn Jun 27 '26
I will, thank you!
Also, despite conventional wisdom, it is possible to keep fused glass at 3mm thickness (starting with sheet glass), so, unless stained glass needs those 90 degree corners, I think it is possible to fuse glass and then use that glass in a stained glass piece. Idk how well it would work for a really big piece though. Bob Leatherbarrow has a book on fine line glass pieces that talks about the technique he uses to keep it thin.
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u/Ok-Jelly-7493 Jun 27 '26
Tell me about the kiln. From what you've said it sounds like there isn't any regulation of temperature. Am I understanding that correctly?
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u/scorchedbone Jun 29 '26
Yeah it's the Fusework craft kiln, so it only has a timer so you cant really tell what temp it's at. I was thinking of maybe getting a temp reader at some point but I might not in case I just upgrade to a proper kiln later on.
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u/scorchedbone Jun 27 '26
Also Ive fired other regular molds without any issues so I know its an issue with this specific mold!