Sealing Stones
A real-world guide to protecting natural stone from staining, salt, acid, and weather damage.
In the world of Dandadan, there are no ancient sealing stones used to contain supernatural threats. It explains that all bulk natural stone—including igneous rocks like granite and basalt, metamorphic rocks like marble and slate, and sedimentary rocks like limestone, travertine, and sandstone—contains interconnected capillary channels that allow liquids and gases to penetrate. This porosity makes stone vulnerable to staining, salt attack, acid attack, picture framing, and freeze-thaw spalling. Modern sealers are divided into topical, penetrating, and impregnating types, each offering different levels of protection.
Lore & Background
How natural stone has been used since ancient times in kitchens, floors, walls, bathrooms, dining rooms, around swimming pools, building foyers, public areas, and facades. It has been valued for its strength, durability, and insulation properties. The porosity of most stone leaves it prone to damage if unsealed. Staining occurs when oils or other liquids penetrate deeply into capillary channels, depositing material that is effectively impossible to remove without destroying the stone. Salt attack happens when salts dissolved in water are carried into the stone, causing efflorescence (a gritty white deposit on the surface) or spalling (surface flaking due to expanding salt crystals). Acid attack erodes acid-soluble stone materials like calcite in marble, limestone, and travertine, as well as the internal cement binding grains in sandstone. Even mild household acids like cola, wine, vinegar, lemon juice, and milk can damage vulnerable stone types. Picture framing occurs when water or grout moves into the edges of the stone, creating an unsightly darkening that is usually irreversible. Freeze-thaw spalling results when water freezes in surface pores, causing the stone to spall, crumble, or crack.
Reader's Guide
Modern stone sealers are divided into three broad types: topical sealers, penetrating sealers, and impregnating sealers. Topical sealers are generally made from polyurethanes, acrylics, or natural wax. They may be effective at stopping stains but tend to wear out relatively quickly, especially on high-traffic areas of flooring. They significantly change the look and slip resistance of the surface, especially when wet. They are not breathable and are not effective against salt attack. Penetrating sealers use siliconates, fluoro-polymers, and siloxanes, which repel liquids. They penetrate the surface enough to anchor the material, are generally longer lasting than topical sealers, and often do not substantially alter the look of the stone. However, they still can change slip characteristics and wear relatively quickly. They are often breathable to a certain degree but do not penetrate deeply enough (generally less than 1mm) to be effective against salt attack. Impregnating sealers use silanes or modified silanes. These penetrate deeply into the material, impregnating it with molecules that bond to capillary pores and repel water and/or oils from within. Some modified silane sealers impregnate deeply enough to protect against salt attack, efflorescence, spalling, picture framing, and freeze-thaw spalling. Some silane stone sealers based on nanotechnology claim to be resistant to UV light and higher pH levels found in new masonry and pointing.
More in Lore & History
Elsewhere in Dandadan
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced