PA Frogskin Glaze

[Kathy Ransom]

I am not certain of the origin of this glaze but I got it from the Prince Albert Arts Center and I believe they got it from the Saskatoon Potter's Guild.

 

Custer Feldspar 22

Gerstley Borate 22

Neph Syen 22

Silica 26

Wollastonite  3

EPK  3

Titanium Diox  2

 

Red Iron Oxide  3

Copper Carb  4

Bentonite  2

 

I sprayed the glaze, applying continuously and working around the piece until the glaze started to run.  This gave me a somewhat thick coat which fired to a nice glossy brown with very funky green spots.

[Cyndy Littleton]

Jeff,

    What did you bisque at after the glaze fire? 06?

Cyndy

[Jeff Poulter]

Usually it is a fast ^06.  If I have something in with a real bisque, then it goes to ^04 on a slow bisque.  It is the time spent up around 900c that allows the RIO to crystallize into the red that you see.  I normally do a 45-60 min hold @ 962c on the way down & that helps, but putting it back in the bisque draws out even more red.  jhp

[Brent Farler]

I second Jeff's comment on throwing it in with a bisque firing , strange but true. The red or iron crystals form at that temp, below that you get green and brown and at higher temps you get black. I have taken ugly greenish brown bowls and included them with a bisque and gotten same ugly bowls but red, ok my bowls have improved but Jeff's vases still trump anything I throw

[Norm Stuart]

This is Frogskin on porcelain fired to ^6 with a very slow-cool from 1,800 F to 1,500 F at 50 F per hour.

I've usually found iron containing glazes lose a lot of iron to clay-binding on white clays. Applied on iron-rich clays, the glazes lose none of their iron resulting in a much different coloration.

I just applied "Clear Base Blue" on iron-rich Amador clay and pulled out some pieces which were golden brown without a hint of blue or green.  On this white clay tile the golden brown is clearly visible only on the breaks in surface texture.

6.0%  Rutile

3.0% Red Iron Oxide

1.0% Cobalt Carbonate

0.8% Copper Carbonate