On Wednesday I was able to warm the garage a little, up to 37, loaded the kiln with work to refire. Cone 6. I programmed in a slow cool with an hour hold at 1800. I have a Skutt 1018 with controller. Things started to look sketchy when after entering the program I hit the review button. The numbers flash by on the display VERY quickly. I rechecked the program about 5 times. Apparently I missed something. Through the evening I watched the firing, then I fell asleep, mistake. When I woke up and checked the kiln it was holding at 1640 F. I have no idea how long it had been at this temp. I'm guessing around 8 hours. One problem I have with this kiln is no matter how I place the witness cones I can't see them during the firing. Being new the peep holes are very small, haven't been worn down any. So I shut the kiln down and waited. I cracked the garage door to help cool down. The garage was very toasty at this time. Once the kiln had reached 540 I quickly cracked the kiln lid to peak in. I was expecting everything to be melted down. Surprise. No melt down of pieces. Last night I unloaded the kiln and took stock of my long hold experiment.
The first pic is of a bowl from a previous firing. I posted about it here: http://community.cer...oles-old-glaze/
The Third pic is same bowl after refiring and long hold. Color is a brown with hints of purple. I had mixed glaze with a few drops of elmers glue and applied over the blisters. barely visible, you can see some of the blisters now just look like unglazed spots. I was using recycled clay, standard 240. I wonder if there was some foreign material in the clay that caused this. On the other items in the kiln being refired it was hit or miss. Items with vertical surfaces fared better that those with flat or or angled surfaces.
Second pic is cone pac from firing. Cones 4, 6, and 5.
Another item in the kiln was some heart pendents. These look pretty good. They are a red glaze. A few were stuck to the bottom of the bead holder I had constructed as the nicad wire had sagged. Conclusion at this time, an 8 hr. soak isn't going to melt everything to the kiln shelf, but some colors look over cooked.