I did a test with ceramic magnets to see if they lost their magnetization
and how much and at what temperatures. I have only been able to find two
brands of ceramic magnets. One type does not actually have a brand name,
but has Made in China Ceramic magnets on the paper inside the bag with the
magnets. The other type is Mangelsen's Craftpro Ceramic magnets, made in
Taiwan. Both sizes were 1/2"X3/16". If you have some magnets and can't
tell if they are ceramic or ***, If you click the ceramic one to your
tooth, it will have a glassy sound to it compared to a dull sound for the
*** magnets. Some of the round *** magnets are hard and it can be
difficult to tell by feel.
I first tested how far apart the magnets had to be from metal or another
magnet to "jump" for its attraction. I set up a Olfa cutting pad with
inches marked under a piece of 1/4 inch glass. I used glass so there would
be as little drag as possible. Then I put it on a wooden table which had no
metal parts. The No-brand China magnets would jump or move when put up to
3/4 " from another magnet, but if one inch away, there was no attraction
noticed. The Mangelsen's ceramic magnets could be 1 1/2" to 1 3/4" from a
metal or another magnet and jump to the object.
First test, I marked the two different types of ceramic magnets. I put
them on a glass container sitting two inches above the metal rack and then
spaced them three inches apart on another piece of glass and placed in the
oven and left for two hours at 300 degrees. Allowed to cool in the oven and
when removed, I placed them at the same spots on the glass covered Olfa
grid. All magnets "jumped" or showed the same attraction as before baked.
Second test, I baked another set of the same type of magnets for two hours
at 550 degrees. Allowed to cool in the oven and performed the same test.
The Mangelsen's magnets showed exactly the same strength as before baking,
however the No brand China magnets had to now be less than 1/2" from a metal
source or another magnet before they moved.
I have already tested the *** magnets and have found that with heating to
clay curing temperatures, the magnets completely lose their attraction.
One other thing, after adding the clay, you will have a little reduction in
magnetization, due to the space taken by the clay between the magnet and the
metal it may need to adhere to. I now use magnets which are double the
strength that I originally thought that I needed.
Hope this is of help to you for using magnets in your pre-cured clay.
Web site http://www.FoundCollection.com/~victoria/sb/