If you want to accent your carving with a brown wash, try 2 Tablespoons of Hazelnut Mason Stain, 2 Tablespoons of Gerstley Borate, and one cup of water.
Brush the stain into carved grooves on bisqued pots. Enhance areas with underglazes.Let dry, and sand with a green scrubby . You can fire without glaze for a rustic surface, or apply a transparent glaze over the surface, or accent with colored glaze.
* for a black wash, substitute black mason stain