Linda Arbuckle kindly submitted the following comments:
"In response to the article about microwaving…. I’ve
had some stoneware cups heat up enough in the microwave to make
the handle uncomfortable to hold. I find wood/salt/soda pieces are
often not vitrified and have this issue, but it’s also happened
with reduction-fired wares. I have heated fake bacon strips on a
porcelain plate and had it crack in 2 (too much localized heat for
a dense body), while earthenware baking dishes have been no problem.
I do microwave Stan Andersen’s majolica plates regularly with
no problems. I don’t think it’s accurate to advocate
no microwaving for earthenware as a group while recommending stoneware
and porcelain carte blanche. It just isn’t so. Depends on
the clay body, firing, and glaze.
I daily microwave my majolica-glaze earthenware cups to make tea
(they do have terra sig on the foot), and they do not explode or
heat up in any uncommon way. They haven’t even crazed.
I think there’s a lot of “iffy” advice out there
about earthenware. The advice on DO microwave stoneware and porcelain
and DON’T microwave earthenware is like everything else in
ceramics: it all depends.
So many of the pottery “sources” knock earthenware w/o
really having solid facts. When I was a student, many of the high-fire
gurus indicated there was nothing worth doing in earthenware, and
even then, leaded was the only way. As an aside, Pete Pinnell has
some interesting info on clay body strength. I’ve appended