This short post on the difference between concrete acid-stains and water-based stains is a supplement to our main post on how you stain concrete.
What is the difference between concrete stain and acid stain?
Acid-based concrete stains interact with the ‘cream’ or top layer of concrete which is a fraction of an inch thick. The reaction with the minerals in the concrete leaves a permanently bonded color that will not chip or peel but must be clear-coated later. Acid stains create a swilling look that is highly desirable and found in many high-end homes. It works on untreated concrete, even if it has a tint, such as the common terra-cotta look. Of course, this will factor into your final color. Always do a test spot! These require a clear coat finish.
These are much easier to apply and does not require clear-coating like acid-based concrete stains. They also come in more colors. Much less preparation is required and it leaves an even, paint-like color. There is some staining of the concrete, but much of the color comes from acrylics that bond to the top of the slab, like paint.
The full details Water Based Concrete Stain vs. Acid Stain
- don’t fade or peel like paint. There was a time all concrete stains used dyes in alcohol, etc and always faded even without sun.
- come many warm, earthy tones and can be mixed to create an infinite variety.
- intentionally leave inconsistencies in the slab: a variegated or mottled appearance, which is subjectively very attractive.
- is compared to, and tries to simulate granite or marble.
- is often used in very ‘high-end’ (meaning expensive) homes.
- require a clear-coating to bring out the depth and to protect the color (and for protection).
The clear-coat I recommend in my main post on staining concrete is one that when needed, does not require any sanding. It re-emulsifies and bonds very well. I recommend (in that post) a top-flight company that makes the full range of products that all play nice together: from prep solutions to the sealant.
Acid concrete staining is a chemical reaction penetrates and changes the actual chemical makeup of the minerals in the slab up to 1/16 inch deep, unlike water-based stains that fill the concrete’s pores and leave a film, somewhat like paint.
Acid stains are made up of metallic salts in an acid and water mix that stain the concrete. The result is random, translucent swirls. The look has deep tones and a simulated marbling look.
- are user-friendly and very safe.
- as easy to apply as paint.
- are available in a wider variety of colors.
- generally require less prep than acid-based stains.
They do not have to be clear-coated (in fact the makers often recommend that you do not clear coat them).
Prep and Application Differences
The prep for acid-based stains must never include muriatic acid etching or grinding, but this is an option for water-based stains. (Some thinkers in the world of paint don’t like the idea of acid-etching, others do. It’s only used to create a roughness “profile” that can accept the coating of your choice: water-based stain, epoxy, paint, etc.
Application methods are not very similar: the acid-based stain needs time to react and darkens with reaction time. Then the acid must be neutralized and rinsed and then sealed. Water-based just dry and that’s it.
The water-based stain goes into the open pores of the concrete somewhat: but it’s also like paint in that it leaves a film or coating on top. No chemical reaction takes place. However, in time, the stain could crack, unlike the acid stain.
Water-based stains are generally low in VOCs (volatile organic compounds) which is a dangerous compound (I have written about VOC’s here). This is not essential reading, but good to keep in mind for life.
If you want a respirator, I simplified the complex world of filters respirator filters and masks here.
After they cure, acid-based stains are as safe as any cured paint. The VOCs they give off while curing are all gone, so always apply and allow to dry and cure with steady ventilation.
Now back to the details of concrete stain. It contains our favorite products and the ‘how-to’ steps for each type of concrete stain.