Surface Preparation

It has been said, "Every step successfully completed leads to the successful completion of the next step." This is certainly the case with chemical-stain work; proper surface preparation is a vital step.

Variablilty, not uniformity, is the current trend. The natural look appeals to many architects and owners.

First, throw a little water on the surface in several locations to see if the concrete absorbs water. If it doesn’t, curing agents or sealers may be blocking the entry of stains and must be removed. Also remove any grease and oil, paint drops, taping compounds, caulk, or other surface contaminants.

Scraping, applying solvents or stripping agents, sanding, and grinding are the principal removal methods. To pick up contaminants more easily, use stripping agents that will mix with water. If you choose to grind the surface, avoid making grinding marks that will reflect through the colored finish by using either a cup grinding head with a fine-grit (diamond or black abrasive) or diamond pad. Use a light touch, laying the cup flat on the concrete and moving it in small-diameter circles until the blemish disappears.

If a slab must be patched, use acrylic-modified, low-shrinkage materials that will accept stain. These patches will always show in the finished product, and the owner should be made aware of this.

To open up the surface for stain penetration, many installers prefer to sand floors using floor buffing machines with #60, #80, or #100 paper or screen-mesh sandpaper that allows dust to pass the pad. This process can add its own pleasing effect to the final appearance by accentuating high and low areas on the surface. (More material is removed from high spots, giving them a richer color.)

The final preparation step involves carefully washing the surface with water and detergent. Don’t use acid to clean the surface because it will diminish the effect of the stain. It’s best to scrub with a buffing machine using strip pads (preferably black) and to pick up the effluent with a good-quality wet vacuum. The surface must be clean and free of streak marks, footprints, and all residues. Anything remaining on the surface will affect stain penetration.


continue – Sawing and Patterning