The surface of plasterboard often has seams, fillers, and leveling compounds that absorb paint differently than the paper surface of the board. Painting directly onto the board can therefore make it difficult to achieve an even finish.
An easy and affordable solution is to attach lining paper or wallpaper liner over the board. Lining paper is generally easier to paint, and a single coat over it may be sufficient. However, light shades or the desired level of opacity may require a second coat. A thin layer of clay plaster also provides a suitable surface for the paint to adhere to.
Standard primers or base coats are not recommended, as clay does not adhere well enough to all primed surfaces. If you wish to apply a base coat, you can use Savella’s Clay shade. It is a textured and highly opaque shade, over which the desired topcoat is applied.