dkat on mon 11 apr 05
Our Pinnell's Weathered Bronze Green had been settling like rock. We had tried increasing the Bentonite and that didn't work at all. I mixed up a Tbsp on Epson salts in a cup of hot water til dissolved. Took about a Tablespoon of this and added it to the remaining 1/4 of a 5 Gallon bucket and MAGIC! No settling at all. The next batch that was mixed up was added the the 1/8th remaining glaze and it is still as smooth and unsettled as can be imagined.
Dave Finkelnburg on mon 11 apr 05
dkat,
You may want to read up on the double layer theory to understand what's really happening when you put Epsom salts in your glaze.
The simple explanation is that adding enough dissolved "salt" to a suspension will increase the viscosity of the suspension. If you add too much, to a too-dense suspension, though, you can make a thick pudding that won't pour except in big clumps.
The double layer thickness is a function of ionic strength of the solution the ion is in, and the double layer thickness determines how close particles can get to each other. If particles can't get close enough to be attracted to each other by electrostatic forces you have a dispersed suspension--one that behaves like water, very thin, almost as if there were no solids present. My understanding is the salt helps the particles get closer to each other, so they start to coagulate and thus don't settle into a dense, hard layer in the bucket.
Good potting!
Dave Finkelnburg
dkat wrote:
Our Pinnell's Weathered Bronze Green had been settling like rock. We had tried increasing the Bentonite and that didn't work at all. I mixed up a Tbsp on Epson salts in a cup of hot water til dissolved. Took about a Tablespoon of this and added it to the remaining 1/4 of a 5 Gallon bucket and MAGIC! No settling at all. The next batch that was mixed up was added the the 1/8th remaining glaze and it is still as smooth and unsettled as can be imagined.
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