Most weeks I receive calls from people asking how to remove a sealer residue. Sealer residues occur when an impregnating sealer is incorrectly applied. Impregnating sealers (or penetrating sealers as they are sometimes known) are intended to be in or below the surface of the stone rather than ‘on’ it. So, the correct application involves applying the sealer to the surface, allowing a short time for penetration (this might be around 5 minutes, depending on both the sealer being used and the material being sealed) then any surplus sealer, remaining on the surface should be removed with something absorbent, ideally a white paper or cotton towel.All too often though, for various reasons thiscleaning away of surplus, whilst still wet, does not take place. Reasons include not reading the instructions and my favourite: “I’ve been using sealers for years, always done it like this and never had a problem.”

A sealer residue can appear in a number of ways: as a dry, white powdery deposit; streaky marks or shiny spots; with some sealers, the residue can take the form of a wet or greasy coating. There are a number of ways in which the problem might be rectified, depending on the circumstances.

For example, if a solvent sealer was used, it is sometimes possible to use a little more of the actual sealer, the solvent carrier-fluid it contains can sometimes re-dissolve the residue allowing it to be wiped away with an absorbent cloth.

For other residues, we would recommend the use of Nanoscrub. First apply a little water to the affected area, and then add a little Nanoscrub and scrub. Rinse well and dry down with paper towels. For really stubborn or thick residues that have been left for some time, a stripper may be required. In such situations we would recommend Sealer & Coating Remover, applied neat and left on for a minimum of 30 minutes before scrubbing with a white nylon pad.

Apart from the last remedy (using a stripper) the others should not result in the need to re-apply more sealer afterwards. So, it need not be the end of the world if a sealer residue is left on the surface, but it is of coarse better to avoid the problem altogether, by applying the sealer correctly in the first place.