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Posted by Bob Masta on October 2, 2006, 8:59 am
Please log in for more thread options On Mon, 2 Oct 2006 09:49:23 +1000, "David Coggins"
>
>> Hmm, I'd be really surprised if the dry-and-regrind changed anything.
>> if the problem is solubles. They'll probably redissolve immediately
>> the next time they see water. (They were originally bound to
>> something else in the glaze, but once they have become free salts
>> it will be just as though you had added the salts in the batch.)
>>
>
>I am no chemist, so I could well be wrong. Certainly if a frit or other
>ingredient has broken down into base materials it will be a waste of time.
>
>I understood that some glaze ingredients, although insoluble over the short
>term, would very slowly dissolve into the water over a long period of time
>(years). Supposedly these would be reclaimed if the glaze was dried and
>reconstituted. Dry, regrind and remix was the recommendation from a large
>premixed glaze manufacturer here in Australia (Cesco) - perhaps this applies
>to fritted glazes only? I must admit that we have only rarely done this, as
>the effort usually outweighs the cost of buying or making a new batch.
>
I am no chemist either, but once the soluble is dissolved in the
water, drying out will surely just leave it as a powdered salt.
I would not expect it to be re-bound to the original minerals just by
drying together with them. What would most assuredly work (if
you were stranded on a desert island with only this glaze and your
kiln) would be to calcine the whole works into a do-it-yourself frit.
I wouldn't think a properly fritted glaze would ever release anything
much into solution... after all, the reason for making a frit in the
first place is to make sure those pesky solubles are no more... their
metals become part of the glass, and their carbonates, etc, are
driven off.
But I agree that it makes a lot more sense to just start over from
scratch, in most real-world situations.
Best regards,
Bob Masta
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