iandol on tue 13 jun 00
Ok here is the deal =85 I have been told by a large hand
full of educators that ceramic ware is microwave
safe..=20
Hello Anji, sorry for the delay. Mistyped the URL
Although Stoneware is regarded as being fully vitrified, which yours =
most likely is, there is always the suspicion that it has a degree of =
porosity which remains. About one percent. This is inevitable because =
during the sintering phase, residual air in the interior of the pot is =
sealed as the grains of clay, silica and felspar fuse. The volume of =
pottery decreases during firing because most of the air is squeezed out =
but that one percent remains. But if this residual porosity remains as a =
slight continuous network water can be absorbed into the ceramic. This =
water changes to steam under influence of the radiation and it=92s =
volume increases a few hundred fold or so. Eighteen grams of water, as a =
gas, can occupy twenty two litres of space, give or take a bubble or so. =
This can cause stress and make a glaze craze, very common in earthen =
ware used for baking. But microwave energy is a bit more instantaneous =
which may explain the Big Bang.
Iron rich glazes absorb microwave energy and this can cause a pot to =
feel hot. And those exposed unglazed areas would allow for greater =
adsorbtion of water.
There should be notes in the archives about tests for pots which are to =
be used in a microwave situation. I microwave our coffee mugs twice a =
day. Cone 8 Stoneware with a clear gloss glaze. No problems. Been in use =
for about eight years now.
Hope this helps,
Ivor.
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