By Mark Atkins, LTP Director
Sealing is often treated as the final stage of a tiling project but, in many cases, it’s something that should be carried out before and after grouting. Porous, natural surfaces like stone and terracotta readily absorb moisture and pigments, so grout can permanently stain the tile face if it’s left unprotected. This is particularly important with lighter-coloured or highly absorbent materials, where even a small amount of pigment migration can leave a noticeable change in appearance.
Problems can arise with both cement and epoxy grout formulations, with common issues including “picture framing”, where grout pigments create darkened edges around the tile. If sealer is applied over grout residue, visible swirl marks are also very common and are caused by the residual grout haze being spread around and sealed into the surface during application. The sealer effectively locks the fine grout particles into place, leaving uneven patterns that become more visible as the sealer cures.
To prevent this, you need to apply a penetrating impregnating sealer before grouting. This creates a barrier that helps prevent grout pigments from being drawn into the tile surface. A good quality sealer will penetrate into the tile’s porosity, allowing the grout to be easily removed from the face of the tile.
It’s essential that the tiles are clean before the application of a sealer, to avoid trapping any residue and dust below this first coat. Any contamination left on the surface will affect sealer absorption and may result in patchy protection after curing. Any surplus sealer should be removed from the tile face around 20-30 minutes after application.
Once grouting has been completed and the joint is fully cured, the tiles should be cleaned again, to remove any remaining grout residue. Once dried, a final coat of impregnating sealer can be applied, making sure to cover the grout joints as well. This helps maintain a more uniform appearance, protects the porous grout joint from stains and makes routine cleaning easier.
Taking the time to apply the protection not only preserves the appearance of the installation but also reduces future maintenance. It also improves overall performance, including maintaining slip-resistant properties of textured surfaces by preventing the build-up of ingrained dirt.
