Do not let the drying temperature go above 212F /100C. (the boiling point of water) or it could explode. The lid/door is open to make sure the pot doesnt get too hot.
About "air pockets" in leatherhard paperclays.
In leatherhard state clays moisture evaporation is incomplete. If wet clays are heated too fast...the mini droplets of water boiling turn to steam that expands before it has a chance to find a path of escape- and risk of explosion is hig. Moisture can find exit out of the interior of ceramic paperclay via the stringlike fiber openings of the paper fiber (cellulose) explained in science section of this site. Risk of explosion is far less with paperclay than with traditional clay as a result. Poking air holes and so on, is rarely needed. Explosion in paperclay can happen but it very rare in a properly balanced body with enough paper in it.
"Toast" dry a fresh soft slab in kiln or direct sun to harden. Extreme example shown here to give the idea above
drying: force dry: dont baby it
Why can we let paperclay dry uncovered, in open air or even near a heat source or direct sun?
Let the natural stress of air dry, or force dry shrinking of the form tell you what sort of movement stress to expect when it moves again in the fire. Its the best "preview" mode ever.
Any weak areas will show up right away. And you get to repair or reinforce them! And the more you re-wet spot areas on the piece for alterations, this also "pre- stresses the structure" just like possible uneven heating inthe kiln will do. By the time you load the dried finished form into the kiln for the real fire stress, you have a very stable form. you have patched its weak areas. Your structure can survive. You saw it expand and contract naturally a few times successfully before it even entered the kiln.Read more more to this in my books.
Traditonal clay construction requires a worker to constantly monitor moisture content, assemble all parts at leatherhard state- usually in a hurry of some kind, then slow dry the whole works carefully and evenly. This process can take weeks, but paperclay is different.
Fact: All big forms will continute to "move" as they shrink and contract in drying after they pass through the leather hard state maybe 10-20%.
In paperclay, therefore, I consider the leatherhard stage to be in fact unstable compared to bone dry. I prefer assembling and working with the super stable- pre shrunk, and strong bone dry state parts.
A ceramic form moves in ultra slow motion when compared to the human form. Paperclays likewise "breathe" in "slo-mo" and the forms expand, pause, contract, pause and move through time, temperature, weather, and more.
The greenware state of traditional big clay is very vulnerable to the kind of catastophic fracture that can't ever be repaired. Compensation for cracks was always part of the process.
Fact: At bone dry the forms "pause" and can't shrink further until kiln heat is applied. In the heat, the sculpture forms first expand a bit at quartz inversion heat (1060F or so) and then contract or shrink as the clay particles gradually melt, merge, vitrifies or matures. (If there is too much heat for too long a time, of course all clay will warp, slump, and at worst melt into a puddle.)
Makers who understand the direction and timing of the two contraction and expansion movements can get precise control with paperclay.
With small works the movement is less obvious. Even so, I love to catch suprises before the fire when I can fix them at bone dry without losing the piece.
Work in Progress: My in progress dried forms with wet joins getting stress tested and force dried in direct sun. Forms like this would be far too fragile to even handle, if made in conventional clay and wet joining dry to dry is not possible. Paradox is that my method saves the total time from start to finish result out of the kiln too.