Question

What is the most reliable, user-friendly, low-VOC, water-based concrete stain available?

Asked by Danna Groden
Overland Park, KS

We are considering Sim Stain, SoyCrete, and Rainbow SS. Do they require any floor preparation other than starting with a clean, non-sealed concrete surface?

Answer

Joel Hirshberg

Answered by Joel Hirshberg

Fairfield, IA

Green Building Supply - your eco-friendly home center

November 22, 2011

Dear Dana,

In order to answer your question fairly and accurately, someone would have to use all three products independently and review their effects over time. I know of no organization that does this type of testing.

  • Therefore, it is up to you to do your own testing of each product and make your own choice.
  • Of course you should read reviews and talk with the manufacturer, however, the bottom line will be how the product works on your concrete.

What I have learned from selling colored stains and sealers for the past 14 years is that coloring concrete is not a DIY type project and is best done by professionals. The number of variables required to get a good consistent result are usually too challenging for most homeowners and here's why:

Before application, most all stained concrete products require that the surface of the concrete be:

  1. clean
  2. dry
  3. neutral pH (7-9)
  4. porous

While these appear to be simple criteria, below are some reasons why they may not be as easy as they appear.

Clean means no dirt, paint, adhesives, drywall mud or sealers that might prevent the stain from penetration. The floor must be washed with a mild detergent. Ideally use a 3000 psi pressure washer. If you are indoors use a damp mop as pressure washing may not be possible.

Be sure to check with the contractor who poured the concrete, if you can find him, as sealers are often used routinely after a concrete pour.

  • One way to check is to simply drip a small amount of water on the floor to see how long it takes to absorb.
  • If it sits there for 1/2 hour or longer, then you may need to use an acid etching solution or a mechanical grinder to remove the sealer.
  • If it soaks right in within a few minutes, then the floor is clean enough.

Dry means more than just dry on the surface. If there is any water inside, it will prevent the stain from soaking in. If it is humid, cold or damp, this could take longer. Be patient. Even if it appears dry on the surface, moisture may still be inside the concrete.

  • There are moisture meters or calcium chloride tests you could use to be sure. If you wait at least two days during warm weather or three days during cool weather it should be fine.
  • Note: New concrete, even though appearing dry, is still very wet inside. Therefore, you must wait a minimum of 14 days until it has dried inside. This can be accelerated with heat, fans and good ventilation.

Neutral is measured with a pH strip or electronic meter. The alkalinity or acidity of the concrete makes a huge difference in how the stain reacts and will produce either a beautiful color or erase the color altogether.

  • Newly poured portland-based concrete has a very high pH of around 14.
  • It can take 6-12 months for the pH to naturally subside depending upon exposure to water, humidity, etc. If you are in a hurry, there are mild acids that can be used to reduce the pH quickly.
  • Older concrete usually has a neutral pH but you have to test it.

Porosity varies widely in new and old concrete. Because concrete cures over many years, the older it is, the harder and denser it becomes. Older homes usually have very porous concrete in the basement or outdoors. But newer residences and commercial buildings often use power-troweling techniques that compress the concrete that make it super smooth, dense and difficult to penetrate. The new WalMarts, for example, have highly polished power troweled floors that resist moisture and colorants.

  • There are mild etching products available to open the pores if necessary, but these cost money and require more labor.
  • That's why many stains are applied or mixed in during the pour and not afterwards.

Choosing the right color may seem relatively easy but what you see in a brochure or on a website will rarely be the color that appears on the floor. Here's why: concrete is mixed differently throughout the country and at different times of the year. The type of cement, lime, stone and other chemicals can vary significantly and as a consequence, will interact differently with each brand of colored stain.

Stains are often different from sealers. If you are considering a stain to help control moisture in your basement, then be sure to read the manufacturers instructions and warranty. Most stains require a sealer to be added afterwards to protect the stain from fading or dissolving. This is true of most tinted concrete and many after-stain products on the market. Be sure to consider the extra costs involved.

Regarding VOCs, all of the above products you mentioned claim their product to be low VOC. I tried to look up their contents in the MSDS provided, however, the first company lists products with names that don't even show up in any chemical database, the second and third claimed their products were proprietary and would not reveal their contents. Unfortunately, this means, you have no real way to compare one against the other nor can you tell if they contain any toxins.

  • Many people have discovered, often after it was too late, that low VOC does not mean non-toxic.
  • Many manufacturers hide toxic ingredients or cover them up with masking agents. The labels may sound good, but there may be chemicals that off-gas for a long time.
  • Unfortunately, our government has allowed companies to get away with this so you have to test things for yourself.

TEST, TEST, TEST. Before you take on this challenge, you need to research your concrete as best you can, test the moisture and pH levels, open up the pores if necessary and then and only then, test the stain to see how it performs.

  • Depending upon how dirty, wet, acidic or dense your concrete is, this task could take days or weeks to perform.
  • It may end up costing far more than you expected and it may not look anything like what you expected.
  • I know that does not sound too encouraging, but you need go into this project with your head up so you are not disappointed.
  • Some people are in such a hurry and want results so badly, they often side-step proper preparation or don't test the concrete properly and the results are not as they expected

Our company, Green Building Supply, offers a competing product called GBS Colored Sealer.

  • It's a water-based non-toxic, ultra-low odor stain and sealer combined.
  • While we consider it a superior product, it still requires all of the above steps for it to work perfectly.

In sum, colored concrete stains can produce a beautiful floor, but they require serious floor prep. If you can afford a professional who has the tools and knowledge to do what the manufacturer requires, then by all means consider using this as an alternative floor covering.

If not, then take a look at other flooring options as there are many eco-friendly products now available.

If you have further questions, please call or email:
joel@greenbuildingsupply
www.greenbuildingsupply.com 

 

For more information:

Read "Is concrete flooring eco-friendly? What's the best way to finish it—stain, paint, polish?" a Q&A answered by Brad Hubbell.

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