Methods you can use to paint clay pottery include:
UnderglazesSlipsOxide stainsGlazesAcrylic paint or fingernail polish
For more acrylic-like effects, you can use liquid underglaze and work with a much heavier, “painterly” style that puts a lot more underglaze on the clay surface. With liquid underglazes, It is best to work in layers, since many are not at full-strength until you have three layers on the clay surface. Be prepared: Dark colors will bleed through overlying layers, even if you cannot see them prior to firing. There are three advantages to using slips:
It is much easier to fully clean off mistakes.Slip painting better matches the clay’s shrinkage, which in turn means less worry about heavier applications popping off during drying or firing.Because the slip painting gets bisqued along with the pot it is on, you can add additional color using underglazes (or other engobes) to strengthen the visual impact or further define the image.
One problem with this method is that the glaze is more likely to flow when it becomes molten during the firing. This can cause designs to sag, become indistinct at the edges, or even disappear into an underlying glaze completely. Two non-ceramic materials can be especially useful for this kind of painting. Acrylic paint is most commonly used, but fingernail polish can also create effective results. Unlike other paints, both these materials have the advantage of being non-water-soluble once they have dried. Besides the lack of functionality, using acrylic paint or fingernail polish has another principle drawback: They can visually flatten and compromise the clay surface they cover. It can be quite hard to visually integrate these materials fully with the clay.
