So the firing speeds that we normally use are too fast, and the remaining water in the pot turns to steam and BOOM! Thick pots need a slower ramp up in temperature during the first 200 degrees, to make sure they dry out. This is why people preheat overnight.
What length of preheating would you recommend for hand built items including coil and slab?
Also I just finished a sculpture of a dog sitting it is about 8x8 inches. I tried to get much of it to the same thickness throughout but there were places where it just had to remain a bit thicker. I plan to let it dry for about a month in my studio with a dehumidifier running to try and lower the overall humidity. When I go to bisque it how long of a preheat would you suggest I try?
Huh.. one month and dehumidifier running? Talk about overkill and massive waste of energy
Set your kiln to 82C (180F) and let it sit there for an hour or 2 and it will be fine.
I use ambient to 82C in 30 min and then few hours for drying (only if needed)
If you have a top loader, you can stick your hand in there and feel is it "steamy" or not.
I had this 45x38 cm (before firing) coil built vase in the kiln for 4 h ... just in case, because I finished it only few days earlier and it was dry outside but not in the inside.
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So I used:
* ambient to 82C - 0.5 h
* 82C-82C - 4 h
* 82C-600C - 5 h
* 600C-1200C - 4 h
* 1200C-1200C - 0.25h
* cool off
I did not to bisque fire, because there was no need and this clay is fine at 1200C
Someone told me that preheating for longer than 20 minutes was a waste of time and energy, ...
If it still steams, it needs more time. Period.
And the energy wasted is way less than "wasted" on building the piece, blowing it up and then building another one and so on...