Ampersand Claybord is an interesting support. It soaks up paint like a sponge, which is great when you are using a method like K.Y.Craft does (airbrush an underpainting of watercolor, seal, then paint with oil.) But try and use straight oils on it and the paint soaks in so fast its like using egg tempera. Frustrating. So I've been attempting to create some texture on a claybord panel by alternating rubbing-in gesso with water mixable oil paints. The result is a very nice, smooth- textured, mottled look, like an old adobe wall.
I rubbed each layer very hard, so the overall surface is still quite smooth and should work well with a detailed painting. (Note: I darkened this image a bit so it would show up here. The actual result is more neutral.) I wanted to create a background with some interest without it being too busy.
It took me over two hours to create this look by building up about nine or ten layers. First I painted a thin layer of gesso over the super smooth panel to give it some tooth. (I know. That defeats the purpose of the claybord.) I didn't let it dry completely. Instead, I rubbed it in with wadded-up paper. (Coffee filters are great for this. They don't fall apart like most paper and they aren't absorbent like paper towels. And they are inexpensive.) I then rubbed on a layer of Indian Red, wiping it off almost immediately. Another layer of rubbed-in gesso and then a very light glaze of lavender, wiped on, then off. After that, alternating rubbings of gesso and a color. ( I used indian red, burnt sienna, raw sienna.) Each layer of paint was thinned with Liquin. I went slowly so each layer would partially dry before rubbing. It was pretty good exercise. My arms are aching!