Will sealing hide stains on pavers?

A clear sealer treats a stain the same way it treats the clean paver around it: it goes on top and stays there.

SEK-Surebond's site preparation bulletin, TB.6, names the result when cleaning is skipped: dirt, spots and residue on the substrate end up sealed in, which the bulletin calls an unsightly look. Whether a driveway can be sealed without a cleaning at all is its own question, under sealing a driveway without cleaning it first.

A sealer does not sit neutral over what is there. ICPI says most sealers darken the paver surface and bring up its color, and Euclid Chemical, writing about concrete sealers, says a sealer highlights differences in the surface texture. A stain is already a difference in the surface, so a finish that deepens and highlights gives it no cover.

Whether sealing makes a paver stain proof is answered under does sealing make pavers waterproof, and how far a given surface's color shifts under whether sealing changes paver color.

ICPI puts the order without a hedge: “All dirt, oil stains and efflorescence must be removed prior to sealing.”

Techniseal gives the reason from the sealer's side. Its Protectors need to penetrate the concrete pores, and ground-in dirt and efflorescence block that, so ground-in residue left behind is also a patch where a penetrating Protector cannot soak in. The full preparation sequence, and the drying condition after it, are under how paver sealing works, step by step. What a degreaser is, and what removing oil from pavers involves, are covered under oil stains on pavers.

For the stain that will not come out, ICPI's stated option is not a sealer: “When pavers have stains too difficult to remove, replace them.”

Once the sealer cures, getting at a stain means getting through the sealer first.

ASCC, writing about concrete sealers, adds a second problem with sealing over a spot: “sealing over these spots may result in poor adhesion or inadequate penetration of the product.” A stain sealed in is not only still visible; the sealer over it may not hold as well as the sealer around it.

A pale haze or line that shows up after sealing is a different fault from a stain, covered under the white line at a sealed edge. None of this is a reading of what is on a particular driveway; it is why the trade cleans first and seals second, and why a stubborn stain is worth pointing out before any sealer goes on.