Glossarhea
Sep. 21st, 2014 10:15 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
offcntrMore terms…
Overglaze and underglaze. Decorative pigments mixed with glass-forming minerals, sometimes clay or a binding material. Some go on the pot and are covered with a clear glaze. Some go on top of the glaze and fuse into the surface in firing. Guess which is which.
Temmoku, celadon. Stoneware glazes, originally from Asia, using iron oxide as a colorant. Celadons are about 2% iron and can be jade green, blue green or olive. Temmoku has about 10% iron, and is generally glossy black when thick, rust red when thin. There are variants with different visual effects, oil-spot, hare's fur. I don't mess with them because I can't paint on them.
Cobalt. Ceramic colorant, usually in carbonate form. Unfired, it's lavender colored and I use it straight as an overglaze. Fired, it's blue. It's one of the constants of the universe: death, taxes, and cobalt blue. Except on rare occasions, where it makes lavender crystals. We don't talk about that.
Raw glazing, single firing. Most people who learn pottery in school fire pots twice. The first, bisque firing is to an intermediate temperature, usually around cone 06, that fixes the clay while leaving it porous. Pots are sturdier and easier to handle, and can be dipped in glaze without risk of them dissolving back into clay. After glazing, they're fired to a higher temperature, cone 10 in my case, which vitrifies (makes glassy) the clay and glazes.
With a little care, however, you can dispense with the bisque firing. Glazes can be applied to raw (unfired) pots, either in the leather-hard or bone dry state. In the former case, you'll need to reformulate the glaze with more clay in it, so it shrinks with the pot as it dries. With bone-dry pots, you can use the same glazes as with bisque. You'll warm up the glaze kiln a little slower when single-firing, but in some situations--wood-firing, for instance--you'd do that anyway.
I used to be a dedicated practitioner of single-firing, from Tuscarora right through graduate school. Working in a crowded Craft Center changed my mind, and now that I have to transport pots from my home studio to the cooperative where I glaze fire, I absolutely bisque fire again.
Overglaze and underglaze. Decorative pigments mixed with glass-forming minerals, sometimes clay or a binding material. Some go on the pot and are covered with a clear glaze. Some go on top of the glaze and fuse into the surface in firing. Guess which is which.
Temmoku, celadon. Stoneware glazes, originally from Asia, using iron oxide as a colorant. Celadons are about 2% iron and can be jade green, blue green or olive. Temmoku has about 10% iron, and is generally glossy black when thick, rust red when thin. There are variants with different visual effects, oil-spot, hare's fur. I don't mess with them because I can't paint on them.
Cobalt. Ceramic colorant, usually in carbonate form. Unfired, it's lavender colored and I use it straight as an overglaze. Fired, it's blue. It's one of the constants of the universe: death, taxes, and cobalt blue. Except on rare occasions, where it makes lavender crystals. We don't talk about that.
Raw glazing, single firing. Most people who learn pottery in school fire pots twice. The first, bisque firing is to an intermediate temperature, usually around cone 06, that fixes the clay while leaving it porous. Pots are sturdier and easier to handle, and can be dipped in glaze without risk of them dissolving back into clay. After glazing, they're fired to a higher temperature, cone 10 in my case, which vitrifies (makes glassy) the clay and glazes.
With a little care, however, you can dispense with the bisque firing. Glazes can be applied to raw (unfired) pots, either in the leather-hard or bone dry state. In the former case, you'll need to reformulate the glaze with more clay in it, so it shrinks with the pot as it dries. With bone-dry pots, you can use the same glazes as with bisque. You'll warm up the glaze kiln a little slower when single-firing, but in some situations--wood-firing, for instance--you'd do that anyway.
I used to be a dedicated practitioner of single-firing, from Tuscarora right through graduate school. Working in a crowded Craft Center changed my mind, and now that I have to transport pots from my home studio to the cooperative where I glaze fire, I absolutely bisque fire again.