Stamped Concrete Guide: Tips for Working With Acid Stains

Applying acid or water-based concrete stains can transform old, dirty concrete surfaces into art. Plus, this type of project is easy to manage once you have the right stain, tools, and equipment. When it comes to acid stains, they can be a bit more challenging to apply than water-based. In this blog post, we’ll highlight some acid stain application tips you can follow to ensure a successful (and safe) project.

Let’s start first by comparing acid and water-based stains, as well as discussing why acid stains tend to be more difficult to apply.

Acid-Based Versus Water-Based Stains

Both acid and water-based concrete stains can yield impressive results. However, there are some key differences between these two products that can help you to determine which will be the best for your projects. Let’s look closer.

Acid-Based Concrete Stains

Concrete acid stains are typically a mixture of metallic salts, water, and hydrochloric acid. Acid stains are reactive, meaning they chemically react with the calcium hydroxide (hydrated lime) contained in the concrete. This reaction lightly etches the surface, and allows the metallic salts to penetrate into the concrete, creating permanent effects that will not chip, peel, or fade.

Please note that acid stains contain volatile organic compounds (VOCs), which make them more dangerous to work with. They also come in a limited array of colors. Additionally, these colors tend to be more neutral “earth” tones.

Typically, acid-based stains are good choices for exterior concrete surfaces, or any concrete surface in harsh environments.

Water-Based Concrete Stains

Concrete water stains are non-reactive, meaning they do not lightly etch the surface of the concrete like acid-based stains do. They do not penetrate into or permanently change the color of the concrete. Rather, they sit atop the concrete surface, like paint, but thinner. Water-based stains are much lower in VOC content and are therefore safer to work with. They are also available in a much broader color spectrum than acid stains. Water-based stains are great choices for interior concrete surfaces, or for homeowners looking for bolder, brighter colors.

Which Stain is Right for You?

Choosing the wrong stain is one of the most common mistakes you can make. If you’re not sure whether or not you need an acid or water-based concrete stain, view this chart below.

The biggest difference between acid and water stains is how they interact with the concrete. Acid stains are reactive; the metallic salts in the acid stains react with the lime in the concrete, which causes the color to permanently change. Water-based stains, on the other hand, are non-reactive and sit on the surface of the concrete. In general, acid stains are more durable and better for use on exterior concrete surfaces.

Materials You’ll Need for an Acid Stain Project

If you’ve determined that an acid stain is the better option for your project, keep reading. Before you start your project, you’ll need to gather a few tools, both for safety and efficiency. These tools include:

• Acid Stain
• All-Purpose Cleaner
• Bristle Brushes
• Mixing Buckets
• Chalk Line
• Concrete Sealer
• Funnel
• Grinder
• Grit Brush
• Mop
• Floor Cleaning Machine
• Painter’s Tape
• Plastic Shoe Covers
• Rubber Gloves
• Safety Glasses
• Low-Pressure Sprayer
• A Certified Ventilation Mask/Respirator
• Wet/Dry Vacuum

Once you’ve gathered these materials, your first step is to prepare your concrete surface.

Preparing Your Concrete Surface

This step is crucial to the success of your project!

Unlike thicker paint that is opaque, acid stains are much thinner and translucent. That means that oil, grease, dirt, and other materials remaining on the surface will very likely show in the final product. Therefore, it is critical to be extra thorough when cleaning and prepping your concrete surface.

Use strippers, grinders, scrapers, and brushes as needed to completely remove any surface stains you don’t want to show through after you apply the stain. Additionally, if your concrete surface has a wax or sealer on it, you’ll want to remove it before applying any stain.

Safety Tips Before Application

As we previously mentioned, acid stains tend to be a bit more challenging to apply than water-based stains. This is because the stains permanently change the color of your concrete, which means that getting it done right the first time is vital. Secondly, acid stains are corrosive and contain high VOCs, which is why you need to wear a respirator, rubber gloves, and safety glasses. Lastly, to prevent inconsistent coloring, we recommend having another person help you throughout the process.

Applying Acid Stains

To ensure a successful and safe application of acid stain, it’s important to follow these steps:

1. Evaluate the stain before you apply it. You’ll want to have a sample that perfectly matches the surface material and color of the concrete you’re staining. Apply the acid stain to the concrete sample first to gain a better understanding of the total burn/reaction time, as well as the final color of the concrete after the stain has been applied.
2. Once you’re ready to apply the acid stain to your concrete slab, you’ll want to mask off doors, door frames, walls, and other areas that you don’t want stained.
3. Add water to the stain to achieve the desired dilution ratio.
4. Check the sprayer’s steam by spraying into a bucket first.
5. Apply the first coat of stain with the sprayer.
6. While you’re spraying the stain across the surface, make sure the other person helping you is using a push broom to evenly distribute the stain.
7. Respray after brushing to diffuse the brush strokes.
8. Use a brush or sponge to coat areas that require precise control.
9. Now, allow the stain to soak into the concrete and dry. It should feel dry in about 15 minutes, but requires up to 24 hours (sometimes 48) to fully cure, depending on the atmosphere. If you want more intense coloring, wait a few hours and then repeat the application procedure.

Cleaning & Neutralizing the Concrete

The job isn’t over yet! After the stain has cured, clean the entire surface thoroughly with water until it runs clear. When using an acid stain, you must neutralize the entire surface with baking soda or TSP that has been dissolved in water. Water-based stains do not require neutralization.

Sealing the Concrete

Lastly, you’ll want to apply a concrete sealer. In general, acid stains don’t require sealers like water-based stains do, but we do recommend it. Sealers add an extra layer of protection to concrete surfaces, which not only extends the longevity of the stain, but also the concrete.

After the baking soda or TSP solution has thoroughly dried, you can apply a concrete sealer. Two coats are generally better than one. Always follow the manufacturer’s instructions. After sealing the pad, you may also choose to apply a protective coat.

More Tips & Tricks for Acid Stains

You don’t want to make mistakes during a concrete staining project, especially if you’re using acid stains. You can avoid some of the most common mistakes, including blotches, visible brush strokes, and streaks, by following these tips:

• Don’t try to handle this job on your own. Attempting to both spray and brush the stain yourself will cause coloring issues.
• Do respray the surface with more stain after it’s been brushed in.
• Don’t skip the safety equipment. Contact with high VOC solutions can cause severe skin reactions, headaches, and eye irritation.
• Do check the spray stream in a bucket first.
• Don’t skip the neutralization process. Some manufacturers may claim that neutralization is not needed for certain acid stains, but the neutralization process can help to increase the longevity of the stain.
• Do spray and brush the acid stain in a circular motion.
• Don’t overspray on sloped concrete surfaces, as that can cause puddling. Instead, lightly spray on the stain.
• Do evaluate the stain first. The final color of your concrete surface will not be the same as the color of the stain when it’s in the bottle.
• Don’t use any metal equipment during the application process, as the acid stain will react to it.
• Do thoroughly plan ahead with the person assisting you during this project. You’ll want to ensure that no one is walking on the stained surfaces throughout the application process.
• Don’t continue with the application process if the stain is fizzing. The acid stain is most likely reacting to a contaminant on the surface that was not removed during the cleaning process. You will need to stop and clean the surface again.
• Do allow the stain to dry for a full 24 hours before adding a second application, if a second application is needed.
• Don’t use a solvent-based cure and seal when staining interior concrete, as it is flammable and hazardous to inhale.
• Do evaluate the sealer you use as well as the stain before applying to your surface. The sealer can change the color of your stain, so evaluating beforehand will ensure no surprises.

Have Questions? Contact Stamped Concrete Today!

Are you starting a concrete staining project? Get everything you need from Stamped Concrete, the leading supplier of acid stains, high-quality concrete staining tools, and other concrete products. Click here to view our complete inventory. If you have questions about concrete staining, or need help finding the right products, contact one of our professionals today!