1/2 cup bleach
1 cup talcum powder
In a glass or enamel bowl, make a paste of the bleach and talcum powder. If cleaning a vertical surface, brush the paste on with a paintbrush and then keep it moist long enough for the bleach to work. After the paste is applied, cover the surface with plastic wrap, sealing the edges with masking tap. Leave on for 24 hours.
Place old newspapers under the surface, remove plastic wrap, and brush the dried paste off with a stiff brush. Rinse thoroughly with a solution of 1/2 cup Soft Soap and 1/2 cup baking soda in 4 cups warm water. Rinse again, if necessary, and dry. Repeat the entire process if necessary.