I have wanted to make a large bowl for a very long time. I thought I could do it, but the more I read, the more I was hesitant to try.
I am by nature an analyzer. This means I like to read everything I can about something before jumping in. You could argue that thinking provides data. On the flip side, too much data can be paralyzing and make you think perhaps you can’t. And so was my internal debate with making my first large fused glass bowl using a large bowl mold (the Kentucky Mold from Blue Fire Molds) which I bought at last year’s Glass Conference in Las Vegas. Five months later, I finally decided to take the plunge.
My first challenge was to make a large 12-1/2 inch fused glass flat plate and well, my first attempt cracked which I lamented in last week’s blog. I decided to go simpler with my second attempt and I made sure to follow good annealing practices! The mold itself is 12-3/8 inches and I was told by Blue Fire that it would be best to have my glass plate slightly larger than the size of the rim of the bowl. My second attempt worked great.
The most challenging part of a large bowl is the slumping process* because it is very easy to have it slump lopsided as I have read many complain about in the fused glass forums. There are plenty of great recommendations available ranging from:
- Ramping the temperature very slowly (50 degrees per hour) from 1050 degrees F to 1225 degrees F,
- Fusing the bowl in multiple steps by starting with a very shallow mold and then going deeper with each subsequent slump,
- Using a donut mold on top of the bowl mold so you end up with a lip and then you can cut off the lip and polish the edges.
All excellent suggestions. If I had a shallow bowl mold, I think I would have started with option 2 above, but since I don’t, and option 3 sounds like a lot of work, I opted for option 1 and took it very slowly. I checked regularly starting at 1050 degrees to see how it was slumping and I was amazed when it appeared done at 1130 degrees F. It is very hard to get a good look inside the mold at such high temperatures to tell if the bottom of your glass is flat and laying on the bottom of the mold, but it looked good, so I moved the kiln program forward to the annealing process.
I could not wait for it to cool and I could take the bowl out of the mold. It worked! I will have to admit that I am feeling pretty lucky. I think having the edge already a little wavy helped. And I am also hoping to buy a shallow bowl mold and try the multi-step process in the future.
I love the look of the large bowl where you can see the light through it and the sun casts the colors onto the table. Well worth the plunge!
* A quick definition of slumping is to fire glass at a lower temperature than fusing temperature, and allow the glass to conform to the shape of a mold (typically ceramic or stainless steel).
NOTE: I learn much of what I know from reading other websites, classes and blogs and hence, I haven’t really invented anything new here. But I am sharing what I found to work and not work. If you have found other ways to do something similar to this, please share!