Thursday, April 1, 2010

Another Learning Experience

As was mentioned in an earlier post, my latest dichroic glass piece cracked. My thought is that I wrapped the metal clay around the glass too tightly. I should have left a little space around the glass to account for the shrinkage. I also mentioned to my students that they could cut a hole in the backing behind the glass (which I forgot to do!) The reason for cutting the hole was to use less clay and to let light through. I do believe the hole also gave the glass a place to go when it was molten, since mine was the only one that cracked. (Everyone else had a hole.) Oh well, another learning experience. At least the crack was in such a place that is isn't at all noticeable.

The second piece was a glass cab I made with frit at the Glass Blower's Center in Hilliards, Pa. I thought I'd try it with metal clay. The piece was wrapped with a coil first and then fired to test it. The glass came through the first firing with very little change. So...... I attached it to an already fired piece, thinking it would be fine. For some reason it changed color (like the beach glass does) and I think it got some devitrification (there is a cloudy spot.) Funny though, for this particular design the cloudy green spot seems to fit. Now I've got to find a chain that also works with it.

The last photo is Phil's finished piece. He decided to add a patina to it. Hard to believe that this was Phil's first piece.


Zoe Nelson said...

Hi Alice - I've fired hundreds of DG cabs with silver clay and never had a problem. What temperature are you firing to? Sometimes I put a hole in the back of the clay, sometimes not. If you're firing below the melting temp. of glass (about 1500F) then the glass cab acts like a "stop" for the clay shrinkage - similar to how a ring pellet would work. I think there might have been a flaw in the glass to start with.

Alice Walkowski said...

Hi Zoe, I thought about it being flawed also. I fire at 1470F as I've read you should. My students glass distorted a little as if it wanted to come out over the clay, which is why I thought maybe my kiln was firing too hot. I'll try again this week and see what happens. Thanks for commenting.

Zoe Nelson said...

I fire glass at 1300F for 1 hour and everything is hunky-dory. (Sorry - should have said that in the first post!)

Alice Walkowski said...

I'll give that a try. Does the glass fuse to the metal at that temperature? The glass split parallel to the back of the piece which is why I think maybe it was defective. It acted like the bottom layer didn't fuse totally. Once it was glued, the crack wasn't visible to the eye.