Black stains around sealant (sealant staining)

Along the sealant of windows and joints, black stains spread into the stone or tile.

Key points

Black stains around sealant (sealant staining) are oils from the sealant that have migrated into the stone or tile and soaked in, with dust then sticking to them. They do not come off by scrubbing the surface. We carry out stain removal that draws the oil out of the stone, and apply a treatment that makes it harder for dirt to soak in. If the sealant keeps releasing oil, the stains may come back.

The photograph is one example. We decide on the cause after checking on site.

Possible causes

Oil contained in the sealant migrates into the surrounding stone or tile and soaks in
Dust sticks to the oil that has seeped out, making it look black

What we check on site

Whether it is surface dust or oil that has worked into the stone
The type of sealant and how far it has deteriorated
The type of stone or tile, and how far the stain has spread

We do not decide on the cause, or whether the work can be done, from photographs alone.

How we deal with it

Draw the oil out of the stone with stain removal suited to the cause (this can be a time-consuming step)
Apply anti-soiling treatment that makes it harder for dirt to soak in
Advise separately if the sealant needs to be replaced

What it cannot do

If oil continues to come out of the sealant, the stains may appear again
It does not fix deterioration of the sealant itself

Before you try it yourself

Rubbing the surface alone will not remove oil inside the stone. Strong solvents can damage stone and sealant.

What affects cost and time

It varies with the depth and extent of the stains, the height and scaffolding, and the type of stone.

The on-site survey and estimate are free. Where there are costs, such as for distant locations or when scaffolding is needed, the installer in charge will tell you in advance.