I found an article online with some interesting and useful information. Here is a synopsis.
Concrete acid stain can be applied to new or old, plain or colored concrete surfaces. They are available in 10 basic colors, though more can be created by combining them. Although they are often called acid stains, acid is not the ingredient that colors the concrete. Metallic salts in an acidic, water based solution react with the concrete to permanently color of the surface. Siliceous aggregates such as gravel or sand, do not react with the stain. Surfaces containing a higher content of cement will react more than one with less cement yielding more intense colors.
Since each surface is different, results may vary from one surface to another. We always recommend testing a small area to determine how the final result will appear. Note that the final color will not be apparent until the sealer has been applied. With wood stain you can still see the grain of the wood through the stain, acid stain is very similar to wood stain as you can see all defects or finishing marks through it, that said, it can give the look of the concrete character, but this depends upon your tastes…I personally am of the believe that little dings, dents, and scratches give Frankie more character, but to each their own.
Factors that may affect the final results include:
- Cement properties and amount used, Admixtures and type of aggregate used.
- Concrete finishing methods, concrete age, and moisture content
- Porosity and Texture of the surface
- Weather conditions when the stain is applied
Concrete acid stain finishes do not require much equipment for the application. The applicator usually uses a garden sprayer that is completely plastic. Some prefer a fine bristle brush or a combination of both. All equipment that will come in contact with the acid stain, such as sprayers, must be resistant to acid. Brushes to apply or spread the stain must be resistant to acid, and also colorless bristles.
Workers must have the proper safety equipment, including acid-resistant gloves, goggles, boots and masks to filter the acid fumes. A good quality wet vacuum is recommended for cleaning. Golf spikes are also recommended because footprints will show through and create undesirable markings in the final appearance.
Surface preparation is considered the most important step in any decorative concrete application. It is important for the immediate and long term performance of all decorative concrete applications. Poor surface preparation can turn a simple process in to a difficult and lengthy repair.
First you will need to throw some water on the surface in several places to see if the concrete accepts the water. If it is not absorbed by concrete, you may have a sealer on your surface. If so, you will need to strip the surface using EnduraPrep Coatings Stripper. This stripper is ideal for removing coatings such as paint or acrylic stains and colorants. If there is not a sealer on the surface, but it will not absorb water, then your surface is too dense. This is usually caused by over troweling of the surface when the concrete was poured. It is very important to condition these types of surfaces to accept the acid stain. Surface conditioning is often the key to success. If it does not accept the water, it will certainly have to be conditioned. Sometimes, very dense surfaces must be conditioned twice. When the surface is conditioned properly, it should feel like sandpaper of 120 grit. To use EnduraColor Reactive Concrete Stain, DO NOT USE hydrochloric acid on the surface because it would deprive the concrete of the necessary minerals to react with the acid stain. There are products on the market which can condition your concrete floor for receiving the acid stain.
The surface must be clean and free of grease and oil, drops of paint, taping adhesive residue, caulk, cement, or any other surface contaminants. All that remains on the surface will affect the final result of the surface.
If patching is necessary, you should use a material with low shrinkage that will accept the stain. The final result will always show these patches. The owner must be aware of this. You might consider doing a concrete overlay if you have many patches, or holes due to carpet tack strip removal.
Decorative patterns with templates can improve the appearance of stained surfaces. The timing of these operations, however, depends on the desired effect. When you want the final appearance to be as even as possible in color, cut lines and patterns after staining is complete. Stains penetrate differently around cuts and indentations. If you want there to be a color change at a pattern line, cut the line first to form a barrier to stain movement. If sawed joints will be grouted, complete the staining and sealing before grouting to help prevent the stain from coloring your grout.
Patterns are usually arranged in pencil or chalk. Mark only where you will cut. Also don’t use chalk that is difficult to remove. Many tools are available for cutting pattern lines in concrete. Most installers use grinders and hand saws with tables, riding against a guide. A 1-1/2 “extruded aluminum” L “angle, available in most hardware stores, will make a good guide. Diamond blades for dry cutting do minimal damage to the edge of the cut. Dust Collectors that attach to grinders and saws are very useful to acid stain applicators.
If patterns are cut before staining, cut just before cleaning the surface prior to staining. Saw dust containing free lime can bind to the surface, causing distortion. If cut after staining, do so after the first coat of sealer has been applied.
We have stained the concrete flooring of many homes and businesses in the Austin area. If you live in Austin, or surrounding area and area interested in getting a quote for concrete stain for your home flooring, or business for that matter, we would love to hear from you!