There is often confusion over different types of sealers. Below is a small article from a very good friend of mine explaining the differences. It is not geared to any particular brand. I hope you find it useful:
TOPICAL or IMPREGNATING SEALER
There are two types of sealer: Impregnating (penetrates and sit below the surface, or 'in' it) and Coating - a topical sealer that sits 'on' the surface. There are pro's and cons to both. Coating sealers sit on the surface, so they are almost always visible, they tend to leave a shine, gloss or low satin sheen, some people think of this as a wet look. This can have the effect of slightly enhancing the colour - and is largely a matter of personal taste as to whether it suits or not). Coating sealers also, seem to make the daily cleaning easier, why?, because they form a physical barrier between the stone and the contaminant. On the down side they are not always as good at resisting certain contaminants (like cooking oil) as their below the surface counterparts. Also, as they are on the surface, they are in the wear zone and so it is the sealer that take the wear (from foot traffic and cleaning chemicals) rather than the tile - so, they wear off much faster, depending on circumstances and the particular sealer, they may need reapplying as often as every other month or as infrequently as 1 to 3 years. So, with coating sealers you get easier cleaning, but more ongoing maintenance, with a bit of a shine.
By contrast, an impregnator will last much much longer (up to 10 or 15 years in some cases). It will not leave an artificial surface coating/shine/gloss etc. It is not in the wear zone so not subject to the effects of traffic and cleaning (to the same extent). The down side, if there is one, is that as it sits in or slightly under the surface, it does not form a barrier on the top. There will always be a fraction of a milimeter of stone that can absorb the contaminant. However this is normal and we need to understand the role of the impregnating sealer:
It is all about REACTION time. The impregnating sealer's job is to keep the contaminant AT THE SURFACE for (and this is key) LONG ENOUGH for you to do something about it (react). I would use an analogy from the carpet world here: You have a new wool carpet, the sales assistant sold you some form of protection treatment for the carpet. You knock over a glass of red wine - do you a.) sit back and say "I'll get to it tomorrow, it's been protected..." or b.) you still run for a cloth and mop up the spill imediately. Hopefully you answered b! - You ran for the cloth, but you did so, with the comforting knowledge that the protection that had been aplied to the carpet, had bought you sufficient time for you to react. - This is what a sealer does for tiles and stone.
Think of an impregnator as a safety net just under the surface to hold a spill or contaminat at the surface long enough for you to clean it away - before it becomes a stain. This is where the difference between a standard and a premium sealer start to become evident. A premium sealer will have much greater resistance to things like oils and the reaction time will be measured in terms of hours rather than minutes.
Sorry if that was a little long-winded but hopefully it explains what sealers can and cannot do. And also shows that what-ever sealer you use, cleaning up oils (which are incredibly efficient at penetrating into stone) at the the earlierst convenience is always the best way to prevent staining.
Reproduced by kind permission of:
Ian Taylor
Celtex Agencies
Kev Martin
Marble Life Ltd
