Ceramic Bead Project Namibia
It started out as trouble, but lead to discovery.
It was December in Africa, where most businesses close down for a month to 6 weeks, and my glaze was not working! Plus I was desperate to get beads finished for my up coming trip to the USA.
After pulling out my hair, crying, praying, screaming.......I remembered my conversation with Deb LeAir about Terra Sigilatta. She makes the most beautiful tiles and not a bit of glaze.http://www.debleair.com/. She had been kind enough to share her technique with me, but I had never actually tried it. Now I was motivated !
Terra Sigilatta is a super refined slip, and has a soft, semi gloss finish, without glaze.
There is a bit of effort initially, but it goes far, and I found it worth the effort. In fact, actually, I'm now in love with it.
White Terra Sigilatta recipe:( From Judy Moonelis via Deb LeAir)
14 cups water
1000grams EPK (kaolin)
500 grams ball clay
7.5 grams Tri Sodium Phosphate ( I could not find this, but successfully used 1 T. Sodium Silicate, and 1 tea. soda ash instead)
Mix the chemicals and the water. Sift in the ball clay and Kaolin. Let slake for an hour or so and then mix really well. I used one of those mixers that fit on your drill. Transfer to a clear glass or plastic container. Let sit undisturbed, (neither shaken nor stirred), for a week, or until you see three distinct layers. The top layer will be water, the middle Terra Sigilatta, and the bottom sludge that you discard.
1. Use a turkey baster or siphon to remove the water layer . From experience, I recommend if you siphon, that you use a long narrow tube. Otherwise you will taste it. 2. remove the terra sig. the same way. 3. throw away the sludge 4. It will be quite thin at this point, so let it sit open to evaporate some liquid and thicken up to something like thin cream. 5. when it's ready, stir, and paint 2 or three coats on bone dry clay, or even bisque. 6. polish with your fingers 7. Bisque at cone 06 8. antique and then fire at cone 04
note: if you are not doing an antiquing step, you don't even have to bisque.
1/3 cup white base
2 T commercial stain or oxide
1/4 tea. 3134 frit ( not necessary if using oxide) Personally I had no luck with the stains. whether it's because we don't have Mason stains here, or because I could not find the exact same frit......don't know? However, I'm quite pleased with the white and with the white plus oxides.
There are a lot of articles on the web about Terra Sigilatta, and many recipes. Some are a bit complicated like the ones needing a hydrometer. Well, in Africa we don't have all the fancy stuff, we make do, and sometimes it even works out better that way.
I experimented adding water and chemicals to my slaked scrap bucket of terra-cotta clay. It made a lovely Terra Sigilatta. The main difference was that the three layers developed in a couple of days instead of a week like the white base recipe.
And my glaze? Turns out, the organic stuff that made the glaze able to be brushed on, had gone bad. A new batch of glaze and we were back in business. But now with a whole new product in addition to the glazed beads.