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volatizing cobalt

updated thu 31 oct 96


Eleanora Eden on thu 10 oct 96

Hi Judy and all,

There was a time that all my decoration was a cobalt slip and I once had
a kiln load where it all seemed to volatilize and land up any old place
it was really dreadful.

In examining the work with a more experienced potter he pointed out that
I had serious "black-coring", or carbonizing of the clay body, in that
firing. This seems to becaused by too much reduction too early in the
firing, as frequently discussed on this list.

So my conclusion was that as well as turning the body a charcoal grey
color the over-reduction caused the brushed-on slip to separate from the
glaze early in the firing.

After that I made sure not to reduce in early stages and didn't see this

Hope this helps. This was about 25 years ago and if the experience can
live on and help others that would be nice.


Eleanora Eden 802 869-2003
Paradise Hill
Bellows Falls, VT 05101