When to Stain Concrete

The work of other trades also can affect staining results. For instance, dry-wall dust on a surface to be stained will react with the stain, coloring the surface differently wherever it’s present. And spills of grease and oil, other lime-based materials, paint, or caulk before or after staining will produce unwanted color variations. A good relationship with the owner or project manager helps to prevent such mishaps. Project management should ensure that the floor isn’t damaged before or after staining and keep other trades away from areas where surface preparation and staining are in progress.
If an installer other than the concrete contractor applies the chemical stain, the contractor and installer must agree on the following:

• Pour schedule. To get a rich color, some installers begin staining with diluted materials as early as a day or two after the concrete has been placed. For uniform results, they need to stain each placement at exactly the same age.
• Jointing method. For slabs requiring sawed control joints or pat-tern lines, dust or sawing slurry must be removed before any of it bonds to the slab. Otherwise, stain color at the joints will differ from the color of the rest of the surface.
• Finishing process. Although Jones likes to work on a hard-troweled surface, some installers prefer finishes that more readily accept the stain. Uniform finishing throughout the job helps to ensure more uniform stain penetration.
• Curing method. Do not use plastic sheeting, liquid membranes, or wet curing methods because they can trap moisture and cause efflorescence.

It’s often best to install chemical-stain finishes and a first coat of sealer, and then protect the floor surface with a cover before allowing other trades on the floor. Unfortunately, any protective material will affect the final appearance of the stained floor to some degree, usually by leaving an outline of its shape on the floor and by darkening the surface a bit. Don’t use any cover material that doesn’t allow water vapor to escape. Breathable cloth tarps are perhaps the best covers for preventing discoloration caused by the work of other trades.

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