I've been trying to fire some glaze test tiles, and as of this morning, I've failed twice.
When I first got my (used) kiln I fired it empty to cone 8 to see if it would work, and it did. Everything went fine. I followed the directions that came with it.
Then I put in round one of test tiles. They all exploded on me, because when the kiln sitter shut off from firing #1, I forgot that all of the power switches were still switched to on. It probably ran for 20 mins before I shut it down.
I made more tiles, and put them in yesterday. However, even after 11 hours of firing, the kiln wasn't getting up to temperature. I was trying to fire to cone 6. I put in a cone 5, 6, and 7 to observe. Cone 5 may have slightly bent, but I'm not sure.
The only difference I can think of is that for this firing I left the bottom peephole open. The directions say to only leave the top peephole open during firing. I also left the bottom open because I needed to see the cones, and I assumed that the open 1" hole would make little difference. During the final hour of firing last night, I closed the peephole in hopes that it would help, but no progress was made in that hour.
Could it be that the peephole being open kept the kiln from getting up to temperature?
I'm really frustrated, and I don't really want to make another set of 20 glaze test tiles for them to get screwed up again. Any ideas?