When a surface is stained, the discoloration is likely due to liquids carrying impurities into the capillaries of the natural stone or other manmade surface such as concrete, grout, brick or other surfaces. The liquid then evaporates or dries and leaves the “stain” under the surface. Cleaning the surface with a cleaning product is the first thing most people try to remove the discoloration. The second, if that does not work, is a poultice.