Beverly Crist on wed 14 mar 01
I use the same glaze as your cone 04 satin matt except with ferro frit 3134
instead of gerstley borate or laguana bortate and I don't have a problem with
crystals. Here's the recipe (not sure where I got it) -
Rice's Satin, cone 04
ferro frit 3134 38
lithium carb. 10
neph. sy 5
add: 2 talblespoons liquid CMC per 1000 gram batch
I like it mixed with 16% red iron oxide for a soft matt brown.
John Hesselberth tested it with copper and the glaze blistered on his clay
body. I've had it blister with copper on certain clay bodies as well, so
you'll have to do some testing. But, I don't have a problem with crystals in
my glaze bucket.