Acid stain has been around for a long time, and most decorative concrete contractors have stained a floor at least once. The process seems so simple, in fact, that many homeowners tackle it as a do-it-yourself project.
While the application itself is relatively simple, there’s a lot more to turning out a complete job than meets the eye. One of the most crucial yet neglected facets involves properly cleaning the residue between the staining and sealing phases.
It’s no wonder this step is neglected. It isn’t detailed in many manufacturers’ literature. Their tech data sheets say to clean and neutralize the residue, but they don’t say how to do it properly. The way most literature reads, simply mopping the floor repeatedly with a neutralizing solution is adequate. According to the instructions, when the rinse water is clear, the floor is clean.
Having used acid stain in commercial environments for several years and seeing firsthand the problems associated with insufficient cleaning, I maintain that this is not the case.
The difference between cleaning and neutralizing
First, cleaning and neutralizing are two entirely different processes. One renders the surface neither acidic nor basic; the other removes all foreign matter.
To put it plainly, residue can be pH-neutral but still present on the surface. Whether or not it’s neutral, it’s still a foreign substance that can affect the topcoat bond. If residue isn’t aggressively removed, it can shorten the sealer’s lifespan or even cause it to delaminate from the slab.
Just like painting over dirt, sealing over residue is a bad idea. Yet that’s exactly what most people do.