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Posted by Bob Masta on October 4, 2006, 8:37 am
Please log in for more thread options On Wed, 4 Oct 2006 06:45:04 +1000, "David Coggins"
>
>>> > Hi Everyone,
>>> > Can glazes go bad?
>>>
>>> Yes ... over time some ingredients of a glaze can get slowly dissolved in
>>> the water. When the glaze is applied to the pot, the dissolved ingredient
>>> is
>>> absorbed into the clay and out of the glaze mix. Hence, the glaze mix is
>>> no
>>> longer complete, and all sorts of problems follow.
>>
>> I was not aware of this. It leads me to ask a question.
>>
>> I am in the habit of keeping 5 gallons of glaze. When the level in the
>> bucket goes down so much that it is hard to apply through dipping, I
>> mix more and add it in. Is it the case that I am susceptable to this
>> problem? I probably go through 5 gallons of my more popular glazes
>> once a year, but others can take longer.
>
>If you are not having any trouble with your glazes, I wouldn't worry about
>it - we have glaze mixes ten years old which are still OK. It probably only
>happens with a small number of ingredients - and in my experience only on
>low fire glazes.
>
My understanding is that colemanite (Gerstley borate and
the like) is supposed to be infamous for this. I use a lot
of this in my glazes and have never noticed a problem, but
then I tend to mix small batches.
Solubles tend to be fluxes, so if they go into solution
and hence are able to penetrate into the body, then
I'd expect the rest of the glaze to have a harder time
melting, and maybe look more matte.
Just a thought....
Bob Masta
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