Cleaning the stain
Cleaning the stain residue off of the floor is the least fun and most laborious part of the project. In a way this is great because it really isn’t that hard. It is, however, critical to remove all residue before the sealant is applied. Excess stain residue is a major cause of sealant failure.
Neutralize the stain residue.
The leftover stain is still very acidic, so it needs to be neutralized. This can be easily (and cheaply) accomplished with a mixture of baking soda and water. You can either mix the baking soda in a mop bucket and apply with a clean mop or you can sprinkle the baking soda on the floor and scrub it in. In the example project we chose to scrub in the baking soda.
Scrub the floor.
Some of the stain residue will be fairly stubborn. We used the same vinyl brush to scrub the floor. This process might take two or more passes in order to get the residue loose. Its a good workout, but don’t cut corners.
Remove the liquid from the floor.
After you have scrubbed the ever-living-&%@$ out of the floor you need to suck up the water. We highly recommend a powerful wet vac from a rental store. They aren’t very expensive to rent for a day and they really get the water off of the floor.
Rinse and repeat.
To ensure that you have removed all residue from the floor, you should repeat the process of scrubbing, rinsing and sucking at least twice. Do not worry about hurting the stain. If your project is working the stain is soaked into the concrete and will not scrape off or be damaged in any other way.
Clean Cloth Test
How do you know if all of the residue is off the floor? Use the Clean Cloth Test. Take a relatively clean piece of fabric (or even a heavy duty paper towel) and wipe it around on the floor. The stain will ruin fabric, so choose your test cloth wisely. If you see residue on the cloth then scrub, rinse and suck!
Let the floor dry.
After you have thoroughly cleaned the floor it will need to dry out completely before sealant is applied. Generally, this means 24 hours. Be patient and let your floor dry out all of the way! You are almost done.
Next: Applying the sealant.