When potters paint on pottery, it is rarely done with what other folk would call paints. We potters tend to paint using other ceramic materials. For myself, I used a variety of underglazes and sometimes slips and oxide stains for painting on clay. All of these fuse to the clay body when fired to maturity, so they are not likely to wear or flake off.
1. Use Underglazes to Paint on Pottery
You can get effects similar to watercolor paintings if your underglaze is both thin enough and has enough colorant in it not to fade over much. For watercolor-like effects, I personally use AMACO's semi-moist underglaze pans. I find them much easier to control than the liquid underglazes when I want wash effects.
For more acrylic-like effects, I use liquid underglaze and work with a much heavier, painterly style. A lot more underglaze ends up on the clay surface in this style. Generally, I also work in layers, since many underglazes are not at full-strength until you have three layers of them on the clay surface.
Be prepared: Dark colors will come through overlying layers, even if you cannot see them prior to firing.
2. Use Slips to Paint on Pottery
I'll also use white or colored slips I make up myself from my clay bodies. (I usually simply save the slip created when I throw.)
Slips are best used on wet greenware. Because of this 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 go back into the painting using underglazes (or other engobes) to strengthen visual impact or further define the image.
3. Use Stains to Paint on Pottery
Oxide stains are wonderful for painting flowing lines as well as adding color to areas. Stains can be commercially prepared stains, which often use fritted material to make them both safer to handle and more chemically stable. Or stains may simply be oxides in water...but you need a good handle on what glaze will go over it. Some oxides are fickle and will change color dramatically depending on what other elements are in the glaze. For example, chrome oxide is generally considered a green colorant but if there is tin in the glaze, it can go pink.
4. Painting with Glazes
One of the ways potters have been painting on ceramics for a very long time has simply been to paint using glazes themselves. This includes glaze-on-glaze painting, such as seen in the majolica traditions, as well as painting various areas with different glazes.
The problem with painting with glaze is that it is more likely to flow during the firing when it is molten. This can cause designs to sag, become indistinct at the edges, or even disappear into an underlying glaze completely.
5. Non-Ceramic Options
We are not limited to ceramic materials if we are not making functional ware. Also, all non-ceramic options are likely to flake or peel off if the piece becomes wet or is placed permanently outdoors.
For ceramic artwork, I have seen people use two main non-ceramic materials to paint with. The one that seems to be most often used is acrylic paint. The other is fingernail polish. Both have the advantage that they are not water soluble once they have dried.
One of the main problems with using these materials to paint on pottery is, besides their lack of functionality, that they often visually flatten and compromise the surface of the clay they cover. It is very hard to visually integrate these fully with the clay in a piece of ceramic art.