“Did you ever do a retest of your Duncan Cover Coats and did you ever photograph the overfired test tiles?”

No, but I’m going to. I’ll probably test to cone 6 and cone 10. I will also expand the test to a vertical surface – and use a cone 6 porcelain and white stoneware (since that’s what I use at home). For cone 10, I’ll test on porcelain and also a white stoneware – not sure which ones yet, because I’m still learning about reduction firing and which clays I like using. I can fire to cone 10 at the Colorado Potters Guild where I’m a member.

I have used cone 10 Babu porcelain and I just picked up a 25lb bag of Zen porcelain that I’m anxious to try out. I know the guild has biz bod, bmix, dover and some other white stonewares – as well as babu, p-60, coleman, and jiki porcelains. I just have to find a couple of cone 10 clays that I like to use.

I just took a quick look at the Mile Hi Ceramic’s catalog and if I were willing to fire to cone 8 in my electric kiln, I could use the clays above – since they’re formulated for cone 8-10, but then I’d have to change all my glazes…

“Did you use the cover coat on greenware or bisque?”

Bisque fire tiles.

“And did you use a clear over them…if so what was the recipe or brand. ”

For my Duncan CC tests, I used 1/4″ flat test tiles and glazed 1/2 the tiles with a homemade clear and left half unglazed. Here’s the link to the tests http://coloradoartstudio.com/2008/07/10/duncan-cover-coat-results/

My recipe for clear is one that’s floating around in cyberspace. This was taken from a notebook binder that Lana Wilson gives workshop attendees.

Gerstley Borate: 50
Kaolin: 20
Silica: 30

It’s brushable – though gets cloudy when applied too thickly.