Sue Leabu on tue 14 feb 06
I want to try a shino slip/glaze recipe that calls for 10% pyrotrol. Does
anyone know what that is, or what can be substituted? The recipe is in the
card set from the Endless Variations exhibition at Baltimore Clayworks
during the last NCECA, recipe #77 from Steve Sauer.
Thanks!
Sue
Mattawan, MI
steve baker on tue 14 feb 06
Dear Sue,
I used to be the tech services engineer for Resco Products who manufactures Pyrotrol at Piedmont Minerals in Hillsborough, NC. Pyrotrol is a natural blend of pyrophyllite and silica and a little andalusite (40% - 50% - 10% mix). The pyrophyllite is the massive type which means it is more like a hard silica rock rather than the greasy, platy foliated type that Vanderbilt produces under the Pyrax names. It is sized at about true 200 mesh. It is a good replacement for silica (we referred to it fondly as "educated silica') in porcelain bodies because it contibutes some alumina (about 21%) which should increase strength. It is white as a powder, but not really a true white product. In a glaze I would suspect that it would raise and widen the maturing temperature, promote opacity, and contribute some fine impurities that may add character. It is a little hard to find in supply houses who favor the Pyrax material. Cedar Heights Clay is part of Resco, and did stock
it. Call William or Angie there at (740)682-7794 and they can either send you a sample or get one sent. 10# may last you a while. They may also be able to tell you someone in your area who may have some. As far as substitution, my best guess would be kaolin + silica, to contribute some alumina. Pyrax may work, but the physical characteristics are so different. Never heard of putting Pyrax in a glaze, though it may work. Resco should have Eric Nedreberg at NCECA. He's minerals manager for Resco.
Steve
Sue Leabu wrote: I want to try a shino slip/glaze recipe that calls for 10% pyrotrol. Does
anyone know what that is, or what can be substituted? The recipe is in the
card set from the Endless Variations exhibition at Baltimore Clayworks
during the last NCECA, recipe #77 from Steve Sauer.
Thanks!
Sue
Mattawan, MI
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