A potential client has a stone patio that had well water leave silica buildup on it (attached are pictures where you can see the white haze). He has since switched to watering everything nearby with reverse osmosis water so if I can remove it the problem won’t come back again.
The question is though, typical acids do not remove silica and I’m wondering if anyone has had any luck with another product or method outside of our usual arsenal?
You’re probably looking at mechanical removal rather than a chemical solution. Remove as much loose material as possible with vacuuming/blowing, then use a pH-neutral stone/tile cleaner with a soft-to-medium nylon brush and scrub until your arms are ready to fall off.
Nmd80. See if that will work for you.
A chemical (like HF) that will remove the silica scale from the surface will also attack the silica in the stone which will etch and permanently discolor the stone. Sidenote, HF is not a nice chemical, it can do permanent damage to your nervous system if ingested. Moot point here anyway since the substrate is silica based too. If this is primarily silica buildup, then I agree with OhioFloMo that this is mostly a mechanical removal process.
A chemical like Redjess suggests will work if the primary components in the buildup aren’t silica. NMD80 is along the lines of any other regular acid based cleaner (think muriatic) and won’t touch the silica component but if its hard water staining then you’d rightly question the homeowner’s claim its silica - surely staining is at least partially based on calcium carbonate/magnesium/efflorescence. In that case NMD80 or something similar would be a good choice but still running a test spot would be prudent before committing to the entire patio.
Thank you and everyone else for the replies. Since I don’t have an NMD80 I think what I’ll do is softwash it with 2-3% rinse off and then pressure wash with 1200 psi at 190° and then see what I’m dealing with after the initial cleaning. I’ll bring a nice big nylon brush to scrub it a bit and I do have some F9 Efflo I could try. Hopefully I get lucky and it’s not silica, maybe just some calcium buildup or some funky efflorescence. I will post before and after pictures of my own and share the results with everybody.
Is it a white/haze/residue or actual granules? I thought I saw more granules while zoomed in…
I’m not sure, the photos were sent to me from the client and being that it’s an hour away I have not been there to see it in person yet. He seems to think that it is silica from the well water leaving Silica behind before he had it fixed to be reverse osmosis. It was sealed initially and many years ago he stripped it and cleaned it with the stripper that was available at the time and used a nylon brush to remove the silica deposits.
