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Print Article Protecting natural stone — and showing consumers how
to properly care for it — not only preserves the beauty of natural surfaces, but it
will also help you protect your hard-earned reputation.
It all starts with understanding the science of stone.
There are many different types of natural stone, just as there are many different types of wood. Each type has characteristics that determine its hardness, durability, chemical resistance, type of finish and even translucency (the ability of light to shine through). By understanding these characteristics, we can make better decisions in the use, maintenance and care of stone.
Why is there so much variation — even in one specific type of stone? Natural stone is not manufactured according to strict laboratory standards. Stone is created in the earth as a product of natural forces. Its origin and composition depends on constantly changing factors such as time and place, heat, pressure and chemistry. This is what makes each stone a unique work of art.
Consumers often assume that natural stone is “stain-proof;” however, all stone is permeable to some degree. In fact, DuPont lab testing shows that all natural stone, including granite, is permeable, and that the lighter and more uniquely patterned natural stones — such as Kashmir White Granite — stain easily. A simple accident of spilling wine or oil on the surface can stain an unsealed countertop in minutes, sending the dissatisfied customer complaining to their supplier.
The best way to prevent staining on natural stone is to treat the surface with a protective sealer. This creates a protective barrier that repels spills on the surface, allowing time to wipe them away. Otherwise, the liquid may damage the stone and leave behind unsightly stains.
All untreated natural stone used in construction is permeable to some degree and should be sealed. It is important, however, to understand that the majority of impregnating sealers used to seal natural stone do not prevent etching of calcite or calcium carbonate based stone by acidic liquids. These stones include limestone, travertine, marble and onyx.
The hardness of a stone is no indication of its permeability to liquids. The factors in determining a stone’s permeability has much more to do with the stone’s composition (silicate or calcium carbonate) and its origin (igneous, metamorphic or sedimentary).
Stones such as granite, gneiss, sandstone, slate, quartzite and schist are made up of silicate minerals. Silicates will have similar chemical resistance characteristics as glass. They are generally not acid sensitive and are relatively hard and/or durable. Limestone, travertine, onyx and marble are all composed of calcium carbonate minerals. They are all acid sensitive and are generally softer than the silicates.
Igneous means “born of fire” and would include any rock formed by the cooling and crystallization of magma (molten rock) or by the consolidation of volcanic ash. Granite is an example of igneous origin. Metamorphic means “changed in structure” and would include any rock that has been altered by temperature, pressure and/or the chemical activities of fluids. Slate, quartzite and marble are metamorphic in origin. Sedimentary means “the cementing of grains,” and would include any rock that is composed of an aggregate of solids derived from preexisting rocks, the precipitation of mineral matter from solution or extracted from solution by organisms. Rocks exposed to weathering or degradation are broken down into smaller particles and may be transported by wind, water or ice and eventually deposited as sediment. Sandstone, limestone, travertine and onyx would be examples of sedimentary origin.
