I made a lot of porcelain pots these past two Saturdays, but alas two of them cracked.
Aaargh. I so love the result of frost porcelain when it has not cracked during its drying in the greenware stage or during its firing in the kiln. And so I did some research on how to not get cracks.
1) Join only pieces of similar dryness and reinforce all joints with extra clay and compress them together with a rib. Compression, compression, compression.
2) Slow and even drying is critical. Periods of rest, where the pieces are wrapped in an airtight chamber to slow drying and redistribute moisture, help. Also restrict movement of the piece during the drying phase.
3) Turning your pots over once they're hard enough to pick up without damaging, may help as it exposes the underside to air.
4) Put your pottery on a shelf or a rack to help the airflow circulate evenly around a piece evenly and prevents certain areas like the underside from holding on to their moisture longer than others.
In looking at the cracked piece above, I think the cookie on which I adhered the rounded slab was so much drier. The bottom and the wall weren't of similar leather hardness or moisture content. Oh well. That wall was so much wetter than the bottom. Live and learn. Here's hoping this bud vase survives drying.
And this larger than a soup bowl too.
I kind of wished that I hadn't adhered that rectangle wider than the circumference of the bud vase on the bottom. I kind of wished that I made the rectangle flush with the walls of the vase. But I worried that it would topple over too easily. Oh the design choices that must be made for a pot to function.
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