Stone or concrete staining is the process by which color is added to stone or stone-like materials through the application of an acid wash. This color is permanent, as the acid etches it directly into the face of the stone rather than simply applying color over the stone. The application process is relatively simple, requiring only a paintbrush and spray bottle.
Clean off the area you wish to stain with your soap and water. The stone should be as clean as possible to ensure a good acid etching.
Mix the acid stain according to the manufacturer's directions in your spray bottle or garden sprayer.
Spray the stone with the acid solution.
Brush the acid solution around on the stone with your brush. This will both work the acid into the stone as well as give it a more "random" appearance, enhancing the aesthetic value of the piece.
Allow the stain to dry, then apply a second coat in the same manner as the first.
Mix a cup of baking soda into a bucket of water and pour a small amount of the mixture over the acid after the second coat has finished drying. Brush the mixture over the acid. Concrete-Stain.com recommends this to neutralize and rinse away any remaining acidic traces.
Wash the stone off with clean water after applying the baking soda mixture.