How did this happen?

[Shelley Lewis]

This was a full fuse on a swirl pattern "fusing mold". No air holes drilled (I had asked on the forum if it needed holes-answer was no). 96 glass with firing schedule: 200 1100 60/50 1250 60/full 1460 12/full 960 60/150 700 0
As you can see, several huge bubbles. Barely any little bubbles (yay-trying to find the silver lining
In addition, glass stuck in mold! Had been properly kiln washed. Seems like it's mechanically stuck in mold. I'm assuming the mold is toast???

[JestersBaubles]

How many layers of glass? Dana W.

[charlie]

if it's mechanically held (by the swirls probably or a slight undercut, turn it upside down and suspend from 1" posts on the edges of the mold only. slowly heat up to annealing temp as a top temp, and listen. if it's not fused to the mold, it should drop off sometime before you get to 1000.

[Shelley Lewis]

Dana,
Two layers plus a little frit on top

Charlie,
Thanks. Will give it a try to save the mold

[charlie]

[quote="Shelley Lewis"]Dana,
Two layers plus a little frit on top

[/quote]

well, i guess it does need holes. the bubbles came from trapped air. if you get the glass off, note where the bubbles where, and drill small holes there (and perhaps elsewhere in the swirl).

[Brock]

And then fuse the blank on a shelf, then slump onto the mold.

[Bert Weiss]

This happened because expanding hot air was trapped beneath the glass at a time when the glass was soft enough to blow bubbles with. Next time, do your full fuse on a flat shelf. Then slump on the mold at a much lower temperature.

So, first, do what Charlie said, and if the hold is mechanical, the glass should fall off as everything expands in the heat. Hopefully around 300ºF. If the glass is stuck to the kilnwash/mold, you must revisit your techniques or your batch of kiln wash.

Glass has a tendency to do those blowout bubbles when part of the glass is 6mm or thicker and part is thinner than 6mm, and, it is hot enough, to be soft enough, to blow out bubbles. When Spectrum forms sheets, they tend to be thicker towards the outer edges, so thinner in the center of the sheet. This creates the possibility that you will have thin places in your layup. I am of the opinion that the thinner (cheaper) Spectrum is a false economy, when you are trying to get away with a 2 layer layup. Spectrum sells by the square foot and Bullseye by the pound, so it is not surprising that that Bullseye is a more consistent 3mm thick. This is not a factor when you are working thicker than 2 layers.

[Shelley Lewis]

Thank you everyone for your help! I was able to remove the glass without heating it after all. This was my first (and possibly last) attempt using a fusing mold. From now on, I think I'll flat fuse first, even if the mold states it is for fusing.

[beninfl]

So how would you know if a mold is suitable for fusing, and slumping? I thought you could only slump with molds, not fuse........ (Super novice, here).

[Brock]

So how would you know if a mold is suitable for fusing, and slumping? I thought you could only slump with molds, not fuse........ (Super novice, here).

Not a bad question though. Personally, I've never fused in a ceramic mold. I have made blanks using kiln furniture and fiber paper when making thicker pieces. Just fuse on the shelf, and use the mold for slumping. Easy . . .

[Laurie Spray]

It would be interesting to see a pic of the entire mold.

[Brock]

http://www.warmglass.com/phpBB/viewtopi ... 11#p351211