John McMillan wrote:
I have some clay pots that I have brought back from Africa, they
are clay that has been fired in a kiln but not glazed.
The clay after firing is a terrcotta colour.

I need to protect them from the UK elements, rain and frost, no
room indoors!


Some of the pots that Ikea (i.a.) sell appear to be dip painted
with
clear acrylic or silicone. The pots are normally made in Vietnam
or Myanmar or somewhere with even worse safety standards but
certainly
no frost. I've often wondered about this technique myself. If I
got
a porous non-frostproof pot and gave it a couple of coats of marine
grade acrylic varnish, then it would be waterproof and so
frostproof,
wouldn't it?

The Vietnamese ones are under-fired as a rule, yes. But you can't
rely on paint or varnish for waterproofing: with weathering and
expansion and contraction the film will crack -- often invisibly --
and these cracks will let in water. Masonry water-repellent, inside
and out, is the only chance, I'd say.

--
Mike.