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deflocculants & copper carbonate

updated wed 25 sep 02

 

Marni Turkel on tue 24 sep 02


A while back I posted a note about trouble I was having
deflocculating a glaze I use that contains copper carbonate. For the
last 2 years or so the copper carb available to me is imported and
really gels up this glaze. I was using Darvan 811 which is
specifically designed for slip clay since I have it around in
quantity. Every few days I had to add more deflocculant to the glaze
and eventually I had a batch get weird and lumpy. I finally had
enough of the problem and decided fix it.

I called the tech guy at Vanderbilt (manufacturers of Darvan
products). He doesn't usually deal with glaze problems. His take on
it was that copper carb was really hard to deflocculate and that
Darvan 7 would be more stable. I switched to Darvan 7 and it is much
longer lasting than the 811 in this application.

I decided to just stop using the copper carb and have switched to red
copper oxide. If you've never tried to mix red copper and water, it
is new experience. I think it was John Hesselberth who said he never
uses it because it is so hard to wet. I am using a non-foaming
agricultural wetting agent, putting it in water with the red copper a
few hours before I want to mix the batch and that is working fine.
The glaze does not gel up, I have no problems with the application. I
used to use 3.5% copper carb, I now use 2% red copper. The raw glaze
on the pot is a pink color that is easily distinguished on the ware
shelves. Most of the other glazes I use which are varying shades of
black or dark, dark grey in the raw state. This lets me easily
separate pieces that would be fumed from the copper in this glaze.

This might not be important to many of you, but it is a major victory to me.

Marni
--

Marni Turkel
Stony Point Ceramic Design
2080 Llano Rd 1B
Santa Rosa, CA 95407

Phone: 707-579-5567
Fax: 707-579-1116
http://www.marniturkel.com