On Saturday, 20 March 2021 at 13:07:31 UTC, Fredxx wrote:


I'm sorry for not replying earlier and thanking you for your excellent
description. Breezing seems to be be a term that has gone out of
fashion, hence no hits.

I do some bronze work, and so aware of gentle heating of ceramic mould
through the 100C mark, to drive out moisture and minimise cracking. I
wasn't aware that pottery, once fired, absorbs water though common sense
suggests it would. I accept that glazes can enclose the ceramic, but in
the lady's example, could some patches of unglazed ceramic be left to
allow the escape of water vapour?

Of course Ceramic moulds can be intentionally made with increased
porosity to assist the pour.

I hear what you say about 'improperly formulated' and I read this as
glazes that would absorb microwaves, rather than making a choice where
absorption is minimal.

Some pottery is fully vitrified, hence unable to absorb water - such as stoneware and porcelain.

Years ago, a place of work had a hotch-potch mixture of crockery in their kitchen. One particular range, a very dark brownish red, was positively dangerous. They would get hotter than their contents.