WarmGlass.com

Hello,
I'm very new to glass art. I bought a kiln that is on excellent condition. Nothing fancy. It has 2 swithes and a timer. I use cones and I do know that the bottom is cooler then the middle. I'm experimenting with 1.5 liter bottles. I put 2 on the bottom at cone 016. Both came out good. No hazy appearance. Here's what happened.
I fired around 3pm, it shut itself off an hour later, took them out around 9am the next day. After an entire day of just sitting on the kitchen counter one of them cracked at 9pm last night. I did a clear one and a dark green one. The green one cracked. I've seen the schedule for slumping and it's very precise and I do believe I need a pyrometer. This was only my 3rd time firing it up and the other bottles I've done didn't crack. Any advise on how to resolve this problem? Also, looking for a good book for a beginner on fusing, etc. any suggestions?
Thanks, Karen

First off, about books...

Contemporary Warm Glass by Brad Walker. He's our host here and his book is very user friendly and comprehensive. You can buy it here, look up at the banner above and click on the Contemporary Warm Glass Book button.

I would say it's not annealed properly. Stress in the glass from improper annealing can show up right away, or years down the road before it cracks.

You have to anneal the glass to remove internal stresses in the glass and you will learn how to anneal from the tutorials on this site, or with your new book.

Karen,

If I understood your post correctly I'd say totally fusing a 1.5 liter bottle in one hour is WAAAAY too fast.

There used to be a tutorial on the board regarding firing bottles.

My suggestion, SLOW DOWN.

Judy

Karen.. I fired in a simple kiln for years.
There are two sizes of cones, so make sure that you're using the smaller ones. I found that 013 are perfect for fusing, and 015 for slumping.
I turn one burner on for several hours in a medium position. You want to keep it under 500° for at least an hour.....
then turn both switches on until it reaches temperature. At this point you can open the door to peak..but shut it and don't open it for anything.

Good luck...... You should have fun with small pieces of jewelry.
Marty