by cleave » Mon Sep 10, 2007 7:48 am
It's actually a "decorative" finish for concrete floors.
"Acid staining is not a dyeing or pigment base coloring systems but a chemical reaction. A mixture of water, salts and acid is applied to the concrete surface and later neutralized by a basic solution, of ammonia and water. Although some manufacturers recommend using baking soda and water, this process increases efflouresence and alkali problems once the surface is sealed.
This chemical reaction with the existing minerals in the concrete creates new colors on the concrete surface. Due to inconsistencies in the surface of concrete, acid staining creates a variegated or mottled appearance that is unique to each slab. The thickness of this color change ranges from 1/16th to 1/32nd of an inch."