Positive results from a rebel
My first kiln was a Skutt G-27 I believe which is a ceramic kiln holding 3 or 4 shelves about 22″ in diameter. It came with the glass studio I purchased and so I had to work with what I had. I now have several kilns, including a very large one just designed for glass but I must be a rebel here and say that I’ve had many successful 3 shelf firings in the Skutt ceramic kiln for fused glass, and one 4 shelf firing which also turned out fine. One needs to understand the principles of firing and the flow of hot air. I carefully put the pieces which are larger and will require the most heat, or composed of “denser” colored glass (white, cream, etc.), or thick and damned, onto the top shelf. I leave as much room as possible between my shelves and as there are no top elements in this kiln I don’t have to worry about stacking toward the lid and it’s problems. And the lower shelves are for pieces that are faster to mature and require a longer, slower firing schedule. I always leave almost double the soak time recommended when I’m multi layering my shelves and it took me a few firings to understand the need for a very different firing schedule to accommocate the more complex nature of multi shelves. But for production glass…it’s great as it will fire the same amount of glass pieces to completion as my Big Bertha (27 x50″) but it cools down almost a full day faster.
In general the advice you have been given here is good and solid…but some of us are rebels and just have to push that envelope…
Windows listen attentively for the sound of broken glass.