This is a coil pot I made quite a while ago... finished it back in June, I think. I glazed it using an orange underglaze, which has a matte finish, and then a glossy glaze sponged over top. The glossy glaze is called "riverstone" and it's a green with shades of brown in it. I wanted the crevices to be the orange matte and then all else to be riverstone...
This was my first experience with underglaze, and it taught me a lot. First of all, the color the underglaze looks before firing is very similar to what'll it be after firing. Underglaze has no glass in it; it's basically colored clay. I thought the orange I was using was too yellow, but having been used to the typical glazes, I didn't really question it. A typical glaze for pottery, that which contains glass, undergoes a chemical reaction during firing, and the color you paint onto your piece before firing doesn't always resemble the color you expect once it's out of the kiln. The orange underglaze came out a dark yellow... kind of a baby poop yellow. I didn't like it at all.
So I took the pot back into the studio, and I mixed red and yellow underglaze for orange, painted it on and then sponged on more riverstone. Painting glaze onto an already glaze-fired pot is not easy. Picking it up and moving it isn't easy, either, because the glaze painted on the glossy areas tends to rub off when you touch it.
Since it's a large piece, about 20 inches or so in height, it took a while to make it into a firing at the studio. I had actually forgotten about the pot... probably so as to prepare myself for it not turning out after its 2nd glaze firing. When Sammy and I got to the studio Saturday morning, it was done. And I am super happy with it... I like the orange so much more than the previous color. The orange is a nice contrast with the river stone glaze.