Sep 23 2014


In part one on stained concrete I talked about the importance of prep work. We had just finished masking off the walls three feet up.

I originally planned to use 1/4″ wide automotive masking tape to mimic grout lines on the dining room floor, giving it a tiled look. The tape would not allow the acid to react or stain to take. At the last minute I changed my mind and didn’t do it. We were beginning to wear down from all the work and I wasn’t completely convinced I liked the idea of faking the look of tile. Looking back, I am glad I didn’t take that time and effort. Instead, I just kept a few dividing lines between the living room and dining room that had already been started. With all the prep work done, it was truly time to get started.

The excitement was high at this point. Finally all of planning and prep work came to this moment, the sizzle of the stain as it hit the concrete. I am not exaggerating about that, you can actually hear it sizzle!

The process of staining concrete is actually acid etching. The stain is acid and pigments. So the sizzle was actually the acid eating away at the top surface of the concrete. I used Kemiko’s Stone Tone “Black” acid stain.


Kemiko’s Stone Tone “Black” acid stain.

To apply the stain, I used a garden chemical sprayer. For the first application, I sprayed a thin layer of the stain diluted with water onto the concrete and let it work. The key here is let “IT” work. I had to resist the temptation to mess with it when the stain didn’t go exactly where I thought it should. Just like the crack I talked about in Part One, leaving the stain alone is part of the natural charm. If it concentrates into dips in the concrete, the best thing to do is to just let it happen. In the finished floor, the only places that don’t look good are the ones I tried to “fix” while the stain was doing its work. The second application was the same as the first, just with the opportunity to apply heavier on areas that appeared lighter during the first pass.

After both applications were dry, I noticed a residue left on the concrete that needed to be cleaned off. Basically, it was a lot of rinsing with water, scrubbing with a deck brush, and removing the dirty water. When I was done with all that, I did it all over again. I knew I was getting close to done when the water starting coming up off the floor clear.

Stained Concrete in Living Room

After floors were stained. The rust colored spots are residue that must be removed.

Technically at this point I was done with the process of concrete acid staining. The concrete was permanently colored but it was dull and felt rough to the the touch. For the finished smooth, vibrant look I really needed a sealer. As I said in the first post, this project was painful and this is the point where it got rough. I had done so much research on the first part of the process, the staining, that I didn’t have a game plan for the second part, the sealing. It was the last day of a four day weekend, and we were desperate to wrap up before Monday. So my dad and I headed to Home Depot to see what we could find.

As we were looking through products, a random guy offered advice saying he had used a water based polyurethane on his garage and it worked beautifully. I was hesitant but had no better ideas so, off we went to check out. Thirty minutes later we were WOWing at the richness of the wet concrete floors. Excitement was high and work progressed quickly. We had it done within an hour. But as the sealer began to dry, an ugly white haze began to form. Some areas began to peel while others looked mediocre.

Wrong Sealer

Good for wood floors, terrible for concrete. No matter what Home Depot guy says.

Stained Concrete With Wrong Sealer

The greenish yellow haze to the left is the sealer releasing from the concrete. In some places it flaked off completely.

A sinking feeling come over me the more I looked at the finished work. I knew this was a step backward, but how far? The weekend had now come to an end. It would have to be a worry for another day.