Prepping concrete for acid staining before getting started is critical to success but how this is done can make or break a project. Here to discuss how to and how not to prepare concrete for acid staining is Shawna Turner, General Manager for Direct Colors.
Amie Nolen: It seems like surface preparation is the most important step of the process. Can this be a big problem for customers if they don’t do it right?
Shawna Turner: Absolutely. Not all concrete can be acid stained but most can if the concrete is properly profiled using the correct product or method before staining. Determining which method or product is best can be the biggest challenge.
AN: Could you explain what it means to profile the concrete?
ST: Sure. Profiling the concrete simply means to change the surface texture to allow for better acid stain penetration. Profiling can be accomplished by either a chemical or mechanical means. Chemical profiling using an acid stain approved etcher such as our DCI Hard Trowel Floor Prep will open the pores without interfering with the later acid staining process. Mechanical profiling would involve a concrete sander or grinder which might be used on extremely smooth or heavily contaminated floors. For example, floors with glue, paint and drywall mud over most of the concrete should probably be mechanically profiled using a grinder because the cost of a chemical strip would be greater than the cost of renting the machine.
AN: What products should not be used to profile concrete?
ST: That’s a pretty easy question to answer. If the etcher is intended for use with anything other than acid stain, don’t use it. That would include water based stains, sealers, epoxy coats, paint and anything else not specifically called acid stain. Acid based cleaners and etchers used in conjunction with other coatings actually dissolve the minerals in the surface of the concrete necessary to support the reaction between an acid stain and the concrete. Without those minerals, the acid stain will sit on the surface and be washed away later in the cleaning process. So if you have previously cleaned your concrete using a muriatic acid and water solution, the slab will either not stain at all or stain very unpredictably depending on how the solution was originally applied and how strong it was. I really can’t emphasize enough that you’ve bought a concrete etching product from a local big box store, don’t use it if you want to acid stain later. Really that’s the bottom line.
AN: Ok. That is straight to the point. How would a customer know aside from obvious surface contaminants that their concrete needs profiling in the first place?
ST: Most indoor concrete and some outdoor poured in the last 10-15 years was likely finished using a machine trowel. We discuss this in some detail on the first page of our How to Guide for Applying Acid Stain. A simple water test will often reveal whether water will readily absorb into the concrete or bead on top. If beading does occur, the surface needs to etched using our DCI Hard Trowel Floor Prep before acid staining. Basement and garage floors are generally the smoothest floors in the house and will more likely than not require etching prior to staining.
AN: So what happens next for customers that have used an acid based etching or cleaning product on their concrete?
ST: I would recommend either Tinted Concrete Sealer or a Tinted Concrete Sealer and DCI Concrete Dye combination to create more color variation and movement on the floor similar to an acid stain finish. If you’re working with outdoor concrete, I suggest our Liquid Colored Antique and Sprayable Satin Finish Sealer. We have a wide color selection and it is extremely easy to apply. I’ve used this product at home on my walkways and patio and have been very happy with it.
If you are in some doubt as to whether your concrete will stain or not, try an acid stain sample bottle and make sure. It’s always a good idea to test the quality of your concrete regardless and it never hurts to try. You’ll find acid stain samples and samples of all our products on our website at http://www.directcolors.com/samples-and-kits/.
AN: Thank you, Shawna, for setting us straight on prepping concrete for acid staining. No doubt this will help a number of homeowners avoid a costly DIY mistake. For more information on acid staining floors and outdoor concrete, visit the blog and featured projects pages of our website, www.directcolors.com.
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