problem and confusion with shower sealing/finishing

[WilliamB]

I'm seeking some advice on how to seal, finish, or more generally treat what I think is a limestone shower to prevent staining and etching that has appeared just a couple months after I last polished and sealed it. I've read a lot of threads on this forum and the general advice in articles on the main site, but am left fairly confused about whether to seal or not, what type of sealer to use, etc. I am a newbie layperson and have not done stone work before, other than taking my badly etched polished marble kitchen countertop down to a honed finish. Here's details:

- History: The shower is 13 years old, in a condo that we bought 3 years ago. I have been thinking of it as limestone, but am not certain. Due to a fair amount of etching, dull tiles, white streaks, etc I bought a variable speed buffer/polisher and some diamond pads from amazon, and sanded it down then brought it up to a glossy polish using MB22 polishing powder. I scrubbed the grout and treated it with a StoneTech anti mildew spray, then sealed everything with StoneTech Heavy Duty Sealer (a water based sealer with fluorinated acrylic copolymer that says it's appropriate for polished stone). The final state wasn't perfect (you can see some circular polishing marks on one of the wall tiles in attached pics), but I was happy with it, and it was a huge improvement, nice glossy finish on most of the tile.

- Problem: Just a couple months after this polishing, a lot of the shelf and floor tile is dull, and you can see a lot of etching on the floor tiles. The white vertical streaks on the wall tiles have started to reappear; I admittedly didn't do as good a job on sanding down and then re-polishing the wall tiles, but they were still better looking 2 months ago. We now squeegee the floor daily, but the walls only get fully squeegeed every few days due to both of us having jobs & sometimes tight/early morning commutes. It's a fairly dry climate here (San Francisco), so after the morning squeegee even the grout dries out about in about 3-4 hours.

- Questions: So what have I done wrong that caused the rapid degradation in finish on the floor, shelf, and wall? Should I have used a solvent-based sealer like the Miracle 511 Impregnator recc'd on johnbridge.com? In some places on this site, even in one of the johnbridge.com articles, I read that we shouldn't seal shower floors because that traps moisture in the tiles ... so maybe I shouldn't be sealing at all? Or do I want to be using some sort of finish that will provide a protective coating, or an enhancing sealer? Or is the only remedy to do a full repolish and then commit to squeegee and towel dry every square inch of tile after every single shower? (we're generally careful and clean, but that is honestly not going to happen with that level of rigor)

In case the uploaded pics aren't sharp enough, I've put higher-res pics here:
photos.app.goo.gl/TSqbNcab2wNgWHFg7

Many thanks for any insight,
William

[John Bridge]

Welcome, William,

I'm not sure what type of stone that is, and it sounds like you used the right type of sealer. I'm hoping someone more knowledgeable than I comes along.

[WilliamB]

Well thank you John. Honestly, the sealer I used (the water based StoneTech) didn't seem to make much of a difference. I was kind of hoping someone would tell me I should use 511, but maybe that's not appropriate for a shower floor.

[John Bridge]

511 is fine. Good stuff.

[Tile & Stone Guild]

Do you have and SDS info on the MB 22? It doesn’t appear to be a traditional acid base or tin oxide formula. It may be it’s more of a coating or temporary polish that needs upkeep. It’s hard to keep polished looking good in a shower if you don’t keep it dry in between uses.