Sealing
Buying time rather than building a barrier. The stone trade corrects the name itself: these are impregnators, and they are repellent rather than stain-proof.
In detail
A sealer applied to a porous surface — stone, grout, unglazed tile, concrete — does not close the pores. The stone institute is unusually direct about this, calling the products impregnators and describing them as repellent rather than a sealer, making stone more stain resistant and specifically not stain-proof. What they do is slow absorption, which extends the window in which a spill can be blotted up before it becomes a stain. That is genuinely valuable and it is a different promise from the one the word implies. Three consequences follow. A sealed surface still needs spills dealt with promptly, and the trade's instruction to blot immediately rather than wipe applies unchanged. A sealer is a wear item that has to be reapplied on a schedule set by traffic and cleaning, not once at installation. And sealing does nothing at all about etching, which is the acid dissolving the stone itself rather than a stain sitting in it — a sealed marble worktop etches exactly as an unsealed one does. A paving manufacturer adds a further caution for outdoor use: it does not stipulate sealants, and warns that one affects colour, appearance and slip resistance.
Why
- Sealing is explained by Porous and non-porous surfaces
- Sealing is explained by Capillary absorption
- Sealing is explained by Etching versus staining
Sources for this page
Sources
Care & Cleaning of Natural Stone
Natural Stone Institute · Trade or professional body
Relied on for: That sealers are impregnators, repellent rather than a sealer, making stone more stain resistant and not stain-proof, and that etch marks are not a cleaning problem but a re-polishing one. (states this directly)
Cleaning & Maintenance Guidelines — Gardens & Driveways
Marshalls plc · Manufacturer documentation
Relied on for: That the manufacturer does not stipulate sealants outdoors, that a sealant affects colour, appearance and slip resistance, and that it must be reapplied over the life of the paving. (states this directly)