Natural Stone Porous Materials Protection Cleaning D.I.Y.

The worst stains and what causes them

Efflorescence is a white powder that can appear on the surface of materials due to salt minerals contained in water.

Many home and business owners enjoy the benefits of natural stone, whether as flooring, wall cladding or countertops.

By employing a high-quality impregnating sealer, such as STAIN-PROOF Originalâ„¢, it’s possible to keep natural stone well-protected from stains while also making surface cleaning easier.

However, an important part of surface protection is understanding what materials cause the most damaging stains to natural stone.

The Marble Institute of America (MIA) breaks down the worst offenders into 10 categories.


Oil-based stains often come from cooking, making them particularly problematic for kitchen countertops. These include stains from grease, cooking oil and milk.

These stains can also come from other seemingly innocuous household items, such as cosmetics.

Stains that are oil-based will darken stone and generally call for some kind of chemical dissolvent to remove them.


Organic stains can be comprised of a wide variety of natural materials, from coffee and tea to leaves and bark.

These types of stains typically leave a pinkish-brown mark. Since there is no shortage of organic materials outdoors, these stains may be more likely on stone located on the exterior of a building.

In these cases, removing the cause of the stain may be all that is required, as rain and sunshine can naturally bleach out stains.

If the stains occur inside, the MIA recommends cleaning with 12 percent hydrogen peroxide and a few drops of ammonia.


Inorganic stains are generally attributed to metal rust stemming from materials like iron, copper and bronze.

These stains are orange to brown in color and typically resemble the shape of whatever left them, be it a nail, screw or can.

Deep-seated inorganic stains can be incredibly hard to remove and may result in the permanent staining of the stone.

However, the MIA recommends using a poultice comprised of kaolin, fuller’s earth, whiting, diatomaceous earth, powdered chalk, white molding plaster and talc.


Biological stains are caused by living materials like algae, mildew, lichens, moss and fungi. A diluted cleaning solution containing water and half a cup of either ammonia, bleach or hydrogen peroxide is recommended.

However, remember not to mix bleach and ammonia, as this can create a toxic gas that can be lethal.


Ink stains often come from the ink found in pens and markers.

Bleach or hydrogen peroxide is recommended for light-colored stone. Lacquer thinner or acetone should be used for darker stones.


Small paint stains can be scraped off, but the MIA recommends commercial liquid paint stripper for heavy stains.

However, acids and flame tools should never be used to remove paint stains, as this can cause a damaging and dangerous reaction.


Water stains can come from everyday activities, such as setting down a glass or spilling water when washing your hands.

The MIA recommends removing water stains by buffing with dry steel wool.

Fire and smoke

Fire and smoke stains can be common occurrences for natural stone fireplaces.

While a thorough cleaning is recommended, smoke remover products are also available.

Etch marks

Etch marks are created when acid is used on some stone surfaces. Calcareous stones such as marble and limestone are particularly susceptible to etch marks and stains.

You can attempt to use polishing powder and buffing to remove etch marks, but deep marks and stains may require the services of a professional stone restorer.


Efflorescence is a white powder that can appear on the surface of natural stone due to salt minerals contained in water. When water from below the surface of the stone rises and evaporates, efflorescence remains.

Using water to clean efflorescence is not recommended, as it is only a temporary solution. You can dust, mop or vacuum the powder, but this may need to be done many times as the stone continues to dry.

If the problem continues, there may be a moisture problem with your stone that requires professional attention.

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