[Clayart] Mica question for Snail and other mica info.

Vince Pitelka via Clayart clayart at lists.clayartworld.com
Sat Aug 30 07:42:42 EDT 2014

Gina Mars wrote:
"Hi All and Snail, I have read most of the mica  posts and I was wondering About the part when you said put on the terra sig and fire it and then apply It again after bisque. I have rarely used it and thought you really need to burnish a piece And bisque it. I thought the terra sig would not work after it's bisqued?"

Hi Gina -
Applying terra sig to bisqueware is always a little precarious, and even with a thin layer it often chips/peels.  Applying it to bisqueware is odd, since it's so much more effective to apply it to dry greenware.  Applying it to damp or leather-hard greenware is risky because the polished terra sig finish has very little capacity for shrinkage and crinkles on a microscopic level as the piece dries, disrupting the shine.  

I hope this doesn't sound picky, but if you have to burnish it to get a shine, then it's not a real terra sig.  Burnishing implies polishing by compressing/rubbing the surface with a hard, smooth, unyielding object like a shiny stone or the back of a spoon, and of course you can get a shine on any claybody by doing that.  A good terra sig can be polished to a high shine with a piece of grocery bag plastic, a soft brush, or a very soft piece of chamois - anything that gets the particles to lay flat and reflect light. So much of the way terra sig behaves depends on whether or not it has been properly prepared.  I certainly don't claim to have come with the best terra sig recipe, but I regularly get positive feedback from people who love it.  For anyone interested, my terra sig article is on my website (link below).  
- Vince

Vince Pitelka
Appalachian Center for Craft
Tennessee Tech University
vpitelka at dtccom.net 

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