Stone sealer

Stone Porosity

All natural stone is porous, which means it has interconnected capillaries through which liquids and gases can move. In fact, porous materials act like a hard sponge and actually suck in liquids over time, along with any dissolved salts and other minerals. More porous stone, such as sandstone will absorb liquids relatively quickly, while denser volcanic stones such as granite are significantly less porous and may take an hour or more to absorb oils and water-based liquids.

Stone as a Building Material

Since ancient times, stone has been popular as a building and decorating material. Its strength, durability, excellent insulation properties, ability to be shaped, and the variety of stone types and colours make it an exceptionally versatile building material.

The porosity and makeup of most stone does, however, leave it prone to certain types of damage if unsealed.

Staining is the most commonly occurring damage, which occurs when oils and other liquids are sucked deeply into the material through its system of capillaries, where it can be impossible to remove.

Salt Attack occurs when salts dissolved in water are carried into the stone. The 2 most common types of salt attack are efflorescence and spalling.

Acid Attack. Calcite-based stone such as marble, limestone and travertine react with acidic substances on contact, breaking down the surface and leaving dull marks or even deep furrows over time. This is known as acid etching. Even mild household acids, including cola, wine, vinegar, lemon juice and milk, can damage these types of stone. The milder the acid, the longer it takes to etch calcite-based stone; stronger acids can damage the stone in seconds.

Protecting Stone

The longevity of stone can be extended if it is effectively sealed against the ingress of damaging liquids and minerals such as salts. The ancient Romans often used olive oil to seal their stone, which provides some protection against the ingress of water and against general weathering by the elements, but stains the stone permanently.

During the renaissance Europeans experimented with the use of topical varnishes and sealers made from ingredients such as egg white, naturally occurring resins and silica, which were clear, could be applied wet and harden to form a protective skin.

Modern Stone Sealers

Modern stone sealers are divided into 3 broad types:

1) Topical sealers - generally made from urethanes or acrylics. These sealers are effective but, being exposed on the surface of the material, they tend to wear out relatively quickly, especially on high-traffic areas of flooring. This type of sealer will usually also change the look and slip resistance of the surface, especially when it is wet. These sealers are not breathable, do not allow the escape of water vapour and other gases, and are not effective against salt attack, such as efflorescence and spalling.

2) Penetrating sealers - the most common of which use siliconates, fluoro-polymers (e.g. Teflon) and siloxanes, which repel liquids. These sealers penetrate the surface of the stone enough to anchor the material to the surface. They are generally longer lasting than topical sealers and often do not substantially alter the look of the stone, but still can change the slip characteristics of the surface and do wear relatively quickly. Penetrating sealers often require the use of special cleaners which both clean and top up the repellent ingredient left on the stone surface. These sealers are often breathable to a certain degree, but do not penetrate deeply enough (generally about 1mm) to be effective against salt attack, such as efflorescence and spalling.

3) Impregnating sealers - which use silanes or modified silanes. These are a type of penetrating sealer, which penetrate deeply into the material, impregnating it with molecules which bond inside and repels water and / or oils from within the material. Some modified silane sealers impregnate deeply enough to protect against salt attack, such as efflorescence and spalling.

External links

* [http://www.marble-institute.com/consumerresources/care.cfm The Marble Institute of America]
* [http://www.flooringguide.com/how-to/stone/sc003.php3 FlooringGuide.com]
* [http://www.brightstn.com Brightstone Stone Care]