Choosing a Topical Colorant: Pros and Cons

Stain can be a choice in choosing a topical colorant - like this stained concrete floor in a restaurant. — When applied, stains penetrate the concrete and react with its chemistry, creating a permanent color. Photos courtesy of Jennifer Faller, Concrete InSite

Architects, designers, customers, owners and most of your staff use the words dye and stain interchangeably. Is there a difference when it comes to choosing a topical colorant? And if so, why does it matter?

Turns out the answer is yes and it matters. Stains are ground, insoluble pigment particles suspended in a carrier solution. On the other hand, dyes are a nano-sized soluble chemical (powder) dissolved in a solution.

Pigment in stains doesn’t dissolve in water. It suspends.
Dye is like salt. It dissolves in water.

Therefore, when you apply stains, and they penetrate the concrete, they react with its chemistry and create a permanent color. Think of the rust stain in your garage.

And when you apply dyes, they penetrate the concrete and stay where they’re left when the carrier (water/solvent) evaporates.

Concrete dyes are another choice when choosing a topical colorant - such as this retail space that was colored with dyes for concrete — When applied, dyes penetrate the concrete and stay where they’re left when the water or solvent-based carrier evaporates.

Stain features and benefits	Dye features and benefits
Acid- or silicate-based carrier Reacts or bonds with concrete Permanent color UV stable Not affected by MVER (calcium chloride test that measures concrete moisture content) Interior or exterior Muted primary colors and earth tones	Water- or solvent-based carrier Penetrates deeper Both easier and faster application Easier to recolor Unlimited color choices Vivid colors Can reapply

Stain limitations	Dye limitations
Limited color density, mostly muted The acid in the stain may either pit or fragment the surface shine Harder to work with Acid stain produces unpredictable color Won’t cover stains, although may somewhat mask them Doesn’t seal or coat the surface Requires a higher level of PPE	Not UV stable; no exterior installations Not alkalinity stable Not reactive/permanent Porous concrete may cause the color to move May not penetrate well with cement replacements such as fly ash or slag Can be affected by MVER >3 pounds/1,000 feet² per 24 hours Doesn’t cover stains, although may somewhat mask them No warranty Doesn’t seal or coat the surface

Acid stain concrete in a grocery store. — Acid stain produces unpredictable color.

Choose the better colorant for each job with confidence, by asking educated questions.

Find out the concrete slab’s age. The age of the slab helps us to determine whether someone placed a moisture vapor barrier underneath the slab. If the slab is 20 years old or less, it’s likely there’s a moisture barrier. It’s certainly unlikely if it’s older than that.

Also, ask if the building is currently conditioned 24/7 and if it always will be. Then do a calcium chloride test if a dye is the design choice.

Yes, the old-fashioned test is better in this case. This is because the vapor-drive is what matters not the percentage of relative humidity (RH). Why? Because the dye can’t tolerate alkaline concrete. If the surface stays dry, it’ll be fine.