What happened?

[Geri Comstock]

The other day I wanted to make some thick pieces of glass out of some old BE scrap I had. The colors I was using were transparent neolavendar and clear irrid. I've done this before with success, and so I'm completely baffled what happened this time.

I used BE dams for two smaller pieces, both in neolavendar. I used thicker home made dams cut out of Thorley shelves for the clear glass piece. All of the dams were well coated with kiln wash; I didn't use paper to line the dams.

I used kiln brick (the same kind my kiln was built from) to support the dams so they wouldn't fall over. Heh. That's happened before.

I ramped slowly (200F) with a 45 minute hold at 1180 to get rid of trapped air bubbles, up to 1530 and held for 30 minutes to get the glass flow evenly in the dams. The final glass pieces were about 1/4 - 3/8" thick.

When I opened my kiln the next morning, a surprise awaited me. The neolavandar glass had literally eaten through the kiln wash into the BE dams and had broken into little bits. A couple of the dams broke in half. A few others had large areas peel off where the glass had eaten into them.

The clear irrid glass I'd fired using homemade dams didn't do this. It was a larger piece than the ones I did with the BE dams, if that might make a difference.

Is there something about neolavendar glass that does this? I've done this same firing before with no problem... Could it be that the BE dams are too thin or something for this kind of application, since it didn't happen with the thicker homemade ones?

The kiln wash I was using was the High Fire version of Hotline. I've used it for 10 years and have never seen glass eat through it before. When I'm finished with this last batch I have, I'll be switching to BE kiln wash.

Baffled Gurl

[Bert Weiss]

The other day I wanted to make some thick pieces of glass out of some old BE scrap I had. The colors I was using were transparent neolavendar and clear irrid. I've done this before with success, and so I'm completely baffled what happened this time.

I used BE dams for two smaller pieces, both in neolavendar. I used thicker home made dams cut out of Thorley shelves for the clear glass piece. All of the dams were well coated with kiln wash; I didn't use paper to line the dams.

I used kiln brick (the same kind my kiln was built from) to support the dams so they wouldn't fall over. Heh. That's happened before.

I ramped slowly (200F) with a 45 minute hold at 1180 to get rid of trapped air bubbles, up to 1530 and held for 30 minutes to get the glass flow evenly in the dams. The final glass pieces were about 1/4 - 3/8" thick.

When I opened my kiln the next morning, a surprise awaited me. The neolavandar glass had literally eaten through the kiln wash into the BE dams and had broken into little bits. A couple of the dams broke in half. A few others had large areas peel off where the glass had eaten into them.

The clear irrid glass I'd fired using homemade dams didn't do this. It was a larger piece than the ones I did with the BE dams, if that might make a difference.

Is there something about neolavendar glass that does this? I've done this same firing before with no problem... Could it be that the BE dams are too thin or something for this kind of application, since it didn't happen with the thicker homemade ones?

The kiln wash I was using was the High Fire version of Hotline. I've used it for 10 years and have never seen glass eat through it before. When I'm finished with this last batch I have, I'll be switching to BE kiln wash.

Baffled Gurl

Geri

It sounds like the neolavendar simply stuck to the dam. Once it has stuck it does not anneal like when unstuck. The lack of annealing caused it to break up. The sticking caused it to tear apart the mullite.

Was the kiln wash fresh or reused?

The strangest thing I ever encountered was with some strange European 1/4" white. Kind of a vitrolite copy. It didn't even stick, as I recall but it crumbled. I was told that it essentialy totally devitrified to the point where it was no longer glass.

[Dani]

Maybe it's a strange year for glass. I had a fused bowl that I used for a cat water bowl.... been doing that job for over a year... break recently. The bottom just flat fell out into the sink re-filling it. Like it rotted out over time, bizarre as that sounds. I know that didn't really happen. But, that's exactly what it looks like. Curious.