scary microburst
Posted: Thu Sep 12, 2013 3:47 pm
I am making a bartop for a local hotel. There are 3 pieces, one 84" x 25" x 30mm, and 2 pieces 26" x 30" x 30mm, with one radiused corner. There is a faux marble painting on top of the bottom 10mm layer. I had the 2 smaller pieces fusing in the kiln. I started about 9:30 PM. Around 7:30 the next day, it started raining, so I went down to the shop to get some things out of the way of the rain. The next thing I know there is lightning and the power goes right out. The firing schedule is a half hour from the end of the anneal soak and drop 100ºF. These are each 4.8 hours, so it had been annealing for 9 hours. I threw the breakers off, so if the power went back on the controller would not try and return where it left off. Power was off for 2 hours. When it came back on, the air temp had dropped below where the program would have it after the next segment, but not too far off. I decided then, that I wouldn't try and heat it back up. Within 15 minutes, the power went out again until around 3AM. This morning, the temp was around 220. I cracked it open and waited until it was 150 to open it up. So far the glass is intact. I think that it will be OK, based on the theory that once far enough below the strain point, you just have to avoid cold shock during the cool down, and stresses will be based on the anneal cycle. The one place I could be wrong here is that the glass could have been close to or above the strain point, sitting hotter than the air. The next step is to grind and polish edges. I am assuming this will show me if there are excessive internal stresses or not.
I am not used to working with dams. This was made from scraps and bricks lying around the shop. It worked well except the 1/4" strip abutted by bricks got some devit. It will polish out.
I am not used to working with dams. This was made from scraps and bricks lying around the shop. It worked well except the 1/4" strip abutted by bricks got some devit. It will polish out.