I don’t know what took me so long to do this project as the results are so valuable. I have three small to medium kilns and have learned over the years which kiln works best for different goals. Ann is a small 8” kiln and works best for jewelry pieces, small dishes, business card holders. Betty, my 14” glass kiln, is my workhorse and where I fire all larger plates. Cindy, is a tall ceramics kiln that my husband resurrected from an auction listing of “bricks”, and is great for vases and frit molds. However you may notice that my descriptions are pretty general, because while I had this high level knowledge, I didn’t really have any specific data to validate the above or help me make decisions on different pieces.
I saw a Facebook post about someone making test tiles and I was reminded that I had put this off for too many years. I took the lull after my Art Festival where I needed to get other things done in my life to make the test tiles. They don’t take much time at all to make, but they take up a lot of time in the kilns to fire each to the right temperature so this was a perfect time to do the test tiles.
I used a Bullseye Technote, Knowing Your Kiln, for the design of the tiles incorporating a high viscosity color – white, with a low viscosity color – black as well as adding frits and stringers of different sizes. Note that the technote is really more for finding hot spots in your kiln which I think would be a different good test for Betty, but I took the test tile design for my kiln temperature test purpose.
The results are so interesting and will help me considerably in the future make decisions for each project on the firing schedule and top temperature. On each tile, I have written the top temperature and either A, B or C for Ann, Betty or Cindy. As you can see in the pictures, a nice contour fuse in Ann is 1425 degrees F, in Cindy it is 1450 degrees F, but in Betty it is only 1375 degrees F.
I had assumed the difference in temperatures between Betty and Cindy was only 10 degrees and so if I was making a large number of something like these dichroic picture frames, I would use both Betty and Cindy and set Betty 10 degrees lower than Cindy and they just never looked the same. Now I know why!
When you get the chance, you really should do your own set of test tiles as I am quite sure over time these tiles for reference will save me time and glass money with more successful projects.