Pretty much the only likely chemical reactions are ones that give off CO2.

Something like a bicarbonate reaction with acid Not saying that's what it is, just more likely. See if the gas puts out a match. You could see if adding a bit of vinegar speeds up the evolution of the gas.

Only other possibilities, both fairly farfetched would be hydrogen (match wil light it - stand back) or hydrogen sulfide (which would be really obvious).

Robert

On Fri, Jan 28, 2022, 08:44 Bryan Johnson <bryj@cheqnet.net> wrote:

When I tumble polish bisqued colored porcelain jewelry I need to "burp" the
barrels after an hour or so due to the gas given off by the porcelain. What
is the gas?
It doesn't happen after high fire.
Bryan
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