Sealing Slate - Information
There are two types of sealer:
- Impregnating Sealers - (penetrates and sits below the surface, or 'in' it) and
- Coating sealers- a topical sealer that sits 'on' the surface.
Pros and Cons
Coating Sealers:
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. 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 impregnators. 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.
Impregnating Sealers:
By contrast, an impregnator will last 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 millimeter of stone that can absorb the contaminant. However this is normal and we need to understand the role of the impregnating sealer:
Reaction Time
It is all about reaction time. The impregnating sealer's job is to keep the contaminant at the surface (this is key) long enough for you to do something about it (react).
Think of it like this, 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 immediately. Hopefully you answered b! - You ran for the cloth, but you did so, with the comforting knowledge that the protection that had been applied 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 contaminant at the surface long enough for you to clean it away - before it becomes a stain.
Standard vs Professional Sealers
This is where the difference between a standard and professional sealer starts 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.
Our own tests
We tested a variety of sealers; from the most expensive to the least expensive. The results were surprising whilst some of the more expensive sealers did a good job in terms of sealing, they made the slate look too shinny and artificial looking. The least expensive sealers did not actually provide adequate protection although they kept the slate looking natural.
Conclusion, well in our opinion the Larsens professional range of impregnating sealer for our Brazilian slate ticked all the boxes.
