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hot mugs

updated mon 30 sep 96

 

ClayBarron@aol.com on sat 31 aug 96

A friend asked me why some of the mugs she has get hot in the microwave and
some don't. I thought it was probably due to water that was absorbed into
the mug during use or washing but I wasn't really sure. Anyone have any
thoughts on this?
TIA! Bill Bryant - Summers over, school is starting and it is HOT!

Nan Dufresne on sat 31 aug 96

>----------------------------Original message----------------------------
>A friend asked me why some of the mugs she has get hot in the microwave and
>some don't. I thought it was probably due to water that was absorbed into
>the mug during use or washing but I wasn't really sure. Anyone have any
>thoughts on this?
>TIA! Bill Bryant - Summers over, school is starting and it is HOT!
>
>The hot cup is due to a hollow handle. I haven't found out why the whole
cup gets hot, but do check that the handle is completely filled with slip now.

Nan Dufresne,NE WI

LEE on sat 31 aug 96

If I'm not mistaken, the mugs are getting hot in the microwave due to
their metallic content.

To test if something should be used in the microwave,
put the piece (mug) in the microwave oven with nothing in it AND next to it
a cup of water in a microwave-safe container. Put the oven on high for
about three minutes or until the water gets very hot or boils.

Afterwards, carefully reach into the oven and touch the empty mug. If
it is hot, you probably shouldn't use it in the microwave. (I'm not
sure whether it is hard on the cup or bad for the oven...I think the
oven might be getting the abuse).

Patsy Catsos on sat 31 aug 96

If there is a lot of metal in the glaze, the mug may get too hot to handle.
I had this problem with a cone 05 glaze that had a lot of copper carbonate
in it.

Patsy Catsos
Cape Elizabeth, ME

John Jensen on sun 1 sep 96

I made a series of mugs four years ago which are the only ones I've ever had to
get hot in the microwave. They were made in a white stoneware and with a clear
glaze and a little decoration with cobalt and copper. The clay was a commercial
body formulated to fire from cone 6 to cone 9; but it was in fact a bit
underfired and overly absorbent at cone 6, which the end point I fired to.. It
never occured to me till now that the moisture in the clay might be reason the
mugs got hot. This is the best explaination I've found..

John Jensen in Annapolis

Barbara Webb on mon 2 sep 96

In my Microwave cookbook it says to put one cup of water in a container
and zap it on High for three minutes. The water should boil and the
container should stay warm enough to touch comfortably. If the container
is too hot to touch comfortably, the book says it is not recommened for
use in the microwave. It does not explain why that is or what types of
containers you could expect to fail this test. Since I read this I test
new claybodies before I make things that I know people would stick in
there. I know this isn't much help but maybe it will give you a starting
point.
Barbara Webb
barbara@fujikura.com
Marietta, GA USA

On Sat, 31 Aug 1996 ClayBarron@aol.com wrote:

> ----------------------------Original message----------------------------
> A friend asked me why some of the mugs she has get hot in the microwave and
> some don't. I thought it was probably due to water that was absorbed into
> the mug during use or washing but I wasn't really sure. Anyone have any
> thoughts on this?
> TIA! Bill Bryant - Summers over, school is starting and it is HOT!
>

Leslie Ihde on mon 2 sep 96

I always thought clays that get hot in the microwave have more metals in
the body- iron etc. After all, you can't put anything metal in a
microwave for that reason
Leslie
Vestal, NY

Ron Roy on mon 2 sep 96

Hi Bill,

I think some of the clay in the mugs is vitrified enough to keep water out.
When water is present in the clay it will heat up in a microwave.

Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849

BobWicks@aol.com on tue 3 sep 96

Hi John:
My experience tells me that high fired wares will be microwave safe and not
be overly hot while lower fired wares are moisture absorbanat and will be
intollerably hot. The principle is that the clay must be fired high enough
so it will not absorb water.

Hope this explains things for you.
Bob

Ron Roy on tue 3 sep 96

>----------------------------Original message----------------------------
>I always thought clays that get hot in the microwave have more metals in
>the body- iron etc. After all, you can't put anything metal in a
>microwave for that reason
>Leslie
>Vestal, NY

My dinnerware (porcelain with Tenmoku glaze) works fine in a microwave -
the glaze has 7.5 % red iron oxide in the recipe. It is easy to test using
the 2 cups one with water and one without. If you are testing make sure the
ware is soaked overnight - pots fresh from the kiln will not have had a
chance to take on any water - which I believe is the real problem.

Ron Roy
Toronto, Canada
Evenings, call 416 439 2621
Fax, 416 438 7849