Actually, I am pretty sure I've seen some pots which were slip-glazed & some
which were self-colored.

Iris, You've been reading!* The term is "vitrification." I've read this* "no
glaze inside or bottom so pot can* "breathe" thing three times in bonsai
magazines last year!
Perhaps you alone can rest the* urban legend! :)

Along with the legends about irregular shaped gravel and humidity trays, no
doubt.
I have about three or so pots which are glazed on the inside. The bonsai do
not care in the least.
I didn't necessarily read this stuff recently. I majored in arts & crafts 55
years ago, including four years of ceramics. Khaimraj has a great deal of up
to date information on the subject.
Iris

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