I was mixing a batch of Steven Hill's Strontium Crystal Magic (warm) and was tired and in a hurry when I got to the Bentonite.  I read across the line wrong and added 2.8 instead of 2.3% bentonite (2.8 is the amount of yellow iron oxide.)

I understand that the effects of bentonite on flocculation reach an optimum peak and then fall off again as the percentage increases.  And I've also read that even messier things may happen.  What I don't know is the breadth of the curve of optimum effect. 

If I need to increase everything else to reestablish percentages I can do that, but I'd rather not if the effect is negligible.

I've just finished a "booth", have a compressor and a sprayer of sorts and am anxious to try spraying glazes.

Here is a humorous article that I wrote elsewhere with pictures of the "booth".

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Im not sure on the answer for the bentonite.. If it was me, I would not make any adjustments, just knowing that the glaze will be a little thicker. I imagine.  Now that spray booth looks like something I would make.  Straight to the point, and easy!  Now tell us after you use it, does it do the job?

J

Chemistry wise there's such a small difference between 2.3% and 2.8%, unless it something like cobalt oxide.

Bentonite used to seal the bottom of ponds and used as a drilling mud additive is rather weak stuff, compared to brand name Veegum or Bentones which have perhaps 10 fold or 15 fold the suspending effect.

I always got the impression that 2.3% Veegum was quite a bit too much with strontium crystal magic. But I've never seen Steven Hill mix it up in person, so I really have no idea.  But when I've run across the occasional recipe calling for 4.5% bentonite I've found it safe to assume they didn't use a very powerful bentonite.

I've only noticed a difference when a recipe calls for a very small amount of clay and I've used bentonite instead. In those cases there's a much higher ratio of silica to alumina in bentonites, say 3 to 1, than there is in clays, which are closer to 1 to  1.

I will give a follow-up on both the glaze and the booth.  It will be interesting to see how long it holds up, and whether my exhaust system works.

juli long said:

Im not sure on the answer for the bentonite.. If it was me, I would not make any adjustments, just knowing that the glaze will be a little thicker. I imagine.  Now that spray booth looks like something I would make.  Straight to the point, and easy!  Now tell us after you use it, does it do the job?

J

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