This Quarry tiled floor is installed in a house that was built circa 1920, well before the invention of damp proof course. Although there was no evidence of damp there was quite a bit of old plaster, trapped dirt and paint splashes on the quarry tiles, the video below gives you a good idea of the state it was in.
Cleaning Quarry flagged flooring
We cleaned the Quarry tiles first with a strong solution of Tile Doctor Pro-clean which improved the floor but struggled to shift the stubborn areas. Something stronger was required to we applied Tile Doctor Grout Clean-Up on the Plaster and Grout followed by a small amount of Tile Doctor Remove and Go to get rid of the Paint Splashes. The floor was then rinsed down with clean water which was then vacuumed off the floor using a wet vacuum and left it to dry overnight.
Sealing Quarry floor tile
The next morning we used a damp meter to verify the floor had dried sufficiently for sealing, it’s always possible to hurry this along with an industrial fan or heat gun for small areas. In this case the floor was fine and we proceeded to seal it using four coats of Tile Doctor Seal and Go which results in a nice low sheen finish as well as providing lasting stain protection, four coats of Seal and Go were needed to seal the Quarry Tiles.
I think you will agree the floor looks transformed.
Source: Quarry Tile Cleaning in Lancashire