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It's very likely that in the process of using sandpaper to clean your tiles you removed the majority of sealant from the Saltillo terra cotta surface, creating a surface which more easily captures dirt. The best bet is to strip, clean and reseal these tiles. If you go the DIY route, you'll have to strip the remaining sealant using something like Aldon Premium Stripper to begin with a clean slate (adding to the remaining preexisting sealant may result in a poor bond between the tile and the sealant protectant). This should remove all dirt and remaining sealant; if a water based sealer was used, a more gentle stripper can be used.

Don't know which sealant was originally used? Here are some detailed tips that might help:

Tips to help identify the family of an unknown sealer:

1. Apply some lacquer thinner to a test area.


2. If the old sealer dissolves completely and tends to penetrate into the surface it could be a solvent based penetrating type. Reseal with another solvent based penetrating sealer.


3. If there is little or no effect on the sealer, it could be a silicone (or other unknown type) and must be considered a high risk situation for any resealing. Consider using Aldon "Lifeguard" only. See also water based penetrating sealer below.


4. If the lacquer thinner makes the old sealer tend to come apart and leave a residue of rubbery particles (like pencil eraser particles) it could be a water based coating type. If so, after stripping it off, water drops should readily and uniformly absorb into the surface. If they do, any of Aldon's sealers can be used. But, categorize the surface as being less absorbent than unsealed material of the same kind. If in doubt, use a solvent base penetrating type.


5. If there is no reaction or change from the lacquer thinner, it might be a water based penetrating sealer. That means there will be sealer below the surface after stripping and the ability to absorb a new sealer, or bond with a new sealer is a concern.  You can test our Same Day Sealer as it is also a water base penetrating type.  To make a change to a new type sealer for any reason, use only Aldon SBS Sealer as it is a solvent base penetrating sealer with the best abiltiy to penetrate into the surface and the best ability to bond with a sealer of an different or unknown type.  However, do a small test area first to confirm there are no surprises.

When you're ready to seal, you can use something like Aldon S-B-S sealer, an acrylic based sealer that does not yellow and has a low gloss shine. Remember to do all these steps on small patches before moving forward. And if this seems daunting, an expert like LA's Best Tile & Grout Restoration may be your best bet.