Most acid stains are a mixture of water, hydrochloric acid, and acid-soluble metallic salts. They work by reacting chemically with the hydrated lime in the stain producing color in the concrete.

When acid stain is applied to a concrete surface it creates a mottled, uneven, translucent color. This coloring process gives the surface a look similar to weathered stone, slate or marble. Since each concrete slab has a slightly different chemical combination colors in concrete can vary. Acid Staining unlike paint is not a coating. Therefore, the color becomes a permanent part of the surface and will not chip, flake or peel. Since acid stain is translucent cracks and other imperfections in the slab give a weathered look of character.

Stain manufacturers differ on when to apply stain. Some say that a new slab must cure for 28 days before work is started. Others suggest 14 days. Installers sometimes prefer to do their work as soon as possible after the concrete is placed.

When choosing how to apply stain, keep the following things in mind:

• Colors are more intense if stain is applied soon after concrete is placed. Stain diluted with water and applied immediately can often achieve the same results as full-strength stains applied later.
• Water drives the chemical-stain reaction. To achieve color consistency, make sure the moisture content of the concrete is roughly the same for every placement colored. If one concrete placement is stained 2 days after its placed, then other placements should be stained when they are 2 days old for color consistency.
• Staining, sealing, and covering finished work before other construction trades return to the area saves on cleanup, achieves a better-looking installation, and makes damage repair during the rest of construction easier to handle.
• More Concrete Staining Issues

Acid staining is not a dyeing or pigment-base coloring systems, but a chemical reaction. A mixture of water, mineral salts and a slight amount of muratic acid is applied to the concrete surface. This chemical reaction with the existing minerals (primarily lime) in the concrete over a period of one to four hours creates new earth tone colors on the concrete surface. The concrete surface is later scrubbed to remove excess stain and neutralized by a basic solution of ammonia and water or baking soda (less likely to cause whiting later) to help raise the ph level back to normal level. Due to inconsistencies in the surface level of concrete floor, acid staining creates a variegated or mottled appearance that is unique to each slab. The color penetration ranges from 1/16 to 1/32 of an inch. Older exterior concrete surfaces may not color as well as interior surfaces because the environment has leached or percolated out the mineral content. As well, any exposed aggregate (rocks) in worn concrete will not accept staining

Proline Dura-Stain Chemical Acid Stain: is a chemical reactive stain developed to permanently transform ordinary concrete surfaces into the beautiful, variegated look of polished stone.

CSI ChromaStain: CSI ChromaStain is a ready-to-use, penetrating, acidic stain that chemically reacts with cured concrete to produce permanent, variegated or translucent color effects. CSI ChromaStain penetrates new or existing concrete to chemically form insoluble, colored precipitates that remain in the concrete’s pores, which means the color won’t chip or fade. CSI ChromaStain may be used with other cementitious materials and natural stones and will provide a unique look and final color to each surface.