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aging deflocculants?

updated wed 21 apr 99

 

Janet H Walker on sun 18 apr 99

Can anyone tell me the shelf life of Darvan #7?

It never occurred to me until NCECA to even think that it had a
shelf life, after all it is an inorganic chemical. But someone
in a panel said that Darvan #811 was effective for only a week
in and that Darvan #7 lasted longer.
So here I am with a slip that is not deflocculated at the "correct"
percentage Darvan #7. Yes, I can add more. But it makes me wonder
whether this particular Darvan has been on the shelf too long.

Also, does anyone know whether all the suppliers sell the same
"strength" of stuff? I mean, it comes as a liquid so you use a
pipette to measure, for example. But is 0.7% of the dry weight of
1000g slip material always the same VOLUME of Darvan #7?

Am I confused? You betcha.

Jan Walker
Cambridge MA USA

Louis Katz on mon 19 apr 99

At the Archie Bray we had some Darvan that had changed color. It was old
(maybe ten years) and had turned slightly coca cola colored. It still
seemed to work like new.
Louis

Janet H Walker wrote:

> ----------------------------Original message----------------------------
> Can anyone tell me the shelf life of Darvan #7?
>
> It never occurred to me until NCECA to even think that it had a
> shelf life, after all it is an inorganic chemical. But someone
> in a panel said that Darvan #811 was effective for only a week
> in and that Darvan #7 lasted longer.
> So here I am with a slip that is not deflocculated at the "correct"
> percentage Darvan #7. Yes, I can add more. But it makes me wonder
> whether this particular Darvan has been on the shelf too long.
>
> Also, does anyone know whether all the suppliers sell the same
> "strength" of stuff? I mean, it comes as a liquid so you use a
> pipette to measure, for example. But is 0.7% of the dry weight of
> 1000g slip material always the same VOLUME of Darvan #7?
>
> Am I confused? You betcha.
>
> Jan Walker
> Cambridge MA USA

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Louis Katz
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David & Diane Chen on tue 20 apr 99

Well I have been following this flocculation thing with a fair amount of
interest, and was understanding most of it. But, does the Daravan additive
and flocculation discussion that Barney initiated with his crawling problem
apply to slips or glazes or both?