Is is possible for glass to get too hot?

[roykirk]

I've got some volcanic ash laying around the shop and for a Sunday project I wanted to experiment incorporating some ash in to glass fusing to see what results I can get. The problem is that volcanic ash doesn't melt until around 2000 F. I can get my kiln that high, but I have no idea what happens if you try to get glass that hot. Will I still be okay if I cool slowly and anneal properly?

[Brad Walker]

The glass will get more and more runny the higher the temperature. By 2000F it will be more like a liquid than a solid and you will most likely need some sort of container (crucible) or barrier (dam) to keep it from running off the shelf. The ash will melt and mix with the glass at temperatures above 2000F. When cooled and annealed, the mixture will solidify.

As I recall, after the eruption of Mount St Helens, a number of glass blowers made objects that combined glass with volcanic ash.

[roykirk]

Thanks for the advice! I'll give it a try today and see what it looks like.

[roykirk]

Didn't end up working. The ash did fuse with the glass in an interesting manner worthy of further exploration, but the glass completely welded to the shelf and then spiderweb cracked on cooling. I'm guessing that my kiln shelf paper wasn't designed to deal with temperatures like that and sort of disintegrated. Back to the drawing board!

[Brad Walker]

I'm guessing that my kiln shelf paper wasn't designed to deal with temperatures like that and sort of disintegrated.

If you used thinfire paper, it's only good up to about 1525F.

If you used fiber paper, each paper has a rating for its maximum temperature.

Firing in a crucible would have probably worked better than on the shelf.