When I am firing my electric kiln, I start with the lid propped open about 2 inches and the top peephole out. Then at around 1000 degrees F I shut the lid. The top peephole is open the whole time. I understand that the lid needs to be propped to allow moisture and gasses to escape in the early stages of firing. My questions are:
1) is 1000F an appropriate temp to close the lid?
2) Is it necessary to prop the lid on a ^6 glaze firing as well as the bisque, or only during the bisque (^06)
I have been firing this way for a couple years and the pots always come out well. However the lid has badly cracked on both the inside and outside, necessitating repair with kiln cement. I have a large electric Skutt Kiln (I think it's the 1227). Even with my repair, it is all fractured and occasionally falls onto the pots below. The metal handle is also badly rusted and corroded, an issue I didn't notice when I bought this kiln used a couple years ago.
I notice when I close the lid on an 1000F kiln it makes a soft settling crackling noise. I am curious if the cracking lid is from thermal shock when it goes from hot room temp to 1000F. Because of this, i wonder if it's better not to close it so late (and hot) in the firing. Perhaps it's just time for an envirovent.
Is it normal for a lid to start to deteriorate like this? The newer versions of my kiln are made with the hydraulic lid lifter, which I assume lifts it more evenly, without the torque from supporting it on just one part. Please let me know if anyone else has had this cracking lid issue.