search  current discussion  categories  glazes - chemistry 

"gastley" borate viscosity problems

updated tue 6 mar 01


Cindy Strnad on sun 4 mar 01


Sorry about the water mention here , but I've found it sometimes works
to add too much water and then siphon it off, add more, siphon it off
several times. This has made some rather thick gerstley glazes workable for

Cindy Strnad
Earthen Vessels Pottery
RR 1, Box 51
Custer, SD 57730

Autumn Downey on sun 4 mar 01

Hello Harold,

You'll likely get lots of answers to this, but I would think a few drops of
Darvan, if you have it - or sodium silicate would deflocculate your glaze.
I didn't have either and used a little trisodium phosphate that was
dissolved in water and it did seem to do the trick. (But it might not be
the best solution.)

I think it's pretty important to only add a small amount of Darvan at a
time. (1 or 2 drops. 5 or so often does it). Sometimes the glaze doesn't
look hugely different, but it does adhere quite differently. And a little
too much deflocculant slows the drying to the point of ridiculous. Testing
this one a piece of bisque after each addition, is sometimes helpful -so
you don't go too far.

Hope you get your glaze problems solved.

Autumn Downey

Yellowknife, NWT

Harold Sarvetnick on sun 4 mar 01

Have a few glazes that have thickened a lot which contain Gerstley- would
love some suggestions to sharply reduce viscosity, that do not include water.
Is there a really strong deflocculant or other additive? or should I just
dump them?

Harold Sarvetnick