While integral colors and color hardeners are used to change the color of concrete as it’s being placed, stains and acetone dyes are used to change the appearance of concrete after it’s placed.
Stains
Stains give concrete a marbled look with varying shades. Traditionally, they were acid-based. Now, water-based stains are used more widely because they are environmentally friendly and require less labor though they're less vivid than their acid-based counterparts. Acid-based stains require contractors to neutralize the concrete with a vinegar or baking soda solution and wash off excess residue from the chemical reaction with the calcium. It’s important to first perform a “hit test,” or sample, with both acid- and water-based stains to ensure the concrete color is as intended. Samples should always be done in inconspicuous areas.
Acetone Dyes
These are similar to stains and are commonly used on polished floors. The acetone carries the dye across the surface and dissipates quickly, leaving the dye, or solids, behind as the color. No additional labor is required. Dyes leave a more consistent color while acid stains leave a marbleized antique color. Dyes are also used for stenciling.
Choosing Between Stains and Dyes
There are many color options. So why would a contractor choose one or the other?
Acid Stains
Acid stains rely on a chemical reaction between the stain and calcium in the concrete. Since levels of calcium vary across the surface, colors with acid stains are not uniform. Each piece of concrete will have its own unique color with a multi-colored marbled look. If the floor has been cleaned with muriatic acid, the acid may not "hit" to provide a vivid color.
Acid stains can be polished but polishing can result in color loss. Dyes are preferred when polishing.
Water-Based Stains
These provide a more consistent color and do not require neutralizing since they are not reliant on a chemical reaction. They're environmentally friendly, more controllable and faster to install. They can also be used for a marbled look if using multiple colors to highlight areas.
Acetone Dyes
Acetone dyes deposit color just as acid stains, but there is a major difference. While the acid stain reacts with the surface of the concrete to create the color, the pigments in acetone dyes are actually absorbed into the pores of the concrete slab. This results in remarkable differences in color between these two options.
Dyes provide colors that are as pale or as bold as you would like – it all depends on how much you dilute the solution before applying it.
Acetone dyes can be polished once application is complete, providing a high gloss finish.
If you want crisp clean color lines, or you plan to use multiple colors, acetones dyes will be the better option. Dyes are preferred for using with stencils to create logos.