Sealing Natural Stone
Several factors must be considered prior to determining if the stone should be sealed:
•What is the hardness, density, and durability of the stone?
•How porous is the stone and how fast will it absorb a liquid (also referred to as the absorption coefficient)?
•Is the stone expected to be in frequent contact with a staining agent?
•What type of finish was applied to the surface?
For example, a polished surface is more resistant
to staining than a honed surface.
•Will the sealant affect the color or other aesthetics of the stone?
•If a resin was applied to the stone, how will the sealant react with the resin?
•Where is the stone located (e.g. countertop, floor, wall, foyer, bathroom, etc.)? Residential or commercial?
•What type of maintenance program has the stone been subjected to?
The type of stone, its finish, its location, and how it is maintained all need to be considered when deter-mining how to protect the stone. In some cases it makes sense to seal the stone. Once properly sealed, the stone will be protected against everyday dirt and spills. In other cases, it is best to leave the stone untreated. Topical sealers can alter the surface texture and finish as well as build up on the surface, creating a layer that is less durable than the stone. Generally, topical sealers are not recommended in exterior applications because they can trap moisture within the top layer of the stone, which may lead to surface deterioration during
freeze/thaw cycles. StoneTex recommends that care be exercised in the application of any chemical to a stone’s surface. Although normally innocent in and of themselves, some sealers have reportedly reacted with some cleaning/maintenance chemicals and/or with components within the stone surface,causing some reactions.
If you have decided to treat your stone, make sure you understand the differences between the types of sealers available on the market:
•Topical Sealers are coatings (film formers) designed to protect the surface of the stone against water, oil, and other contaminants. They are formulated from natural wax, acrylic, and other plastic compounds. When a topical sealer is applied, the maintenance program often shifts from a program focused on stone care to a program focused on the maintenance of the sealer (for example: stripping and reapplication).
•Impregnators are water- or solvent-based solutions that penetrate below the surface and become repellents. They are generally hydrophobic (water-repelling), but are also oliophobic (oil-repelling). Impregnators keep contaminants out, but do not stop the interior moisture from escaping. These products are considered “breathable,” meaning they have vapor transmission.
Vanity tops and food preparation areas may need to have an impregnator applied. Check with your installer for recommendations. If an impregnator is applied, be sure that it is safe f or use on food preparation surfaces. If there are questions, check with the product manufacturer. Before sealing, always:
•Read the Manufacturers Warranty and Instructions.
•Contact the manufacturer prior to application if you are unsure or need clarification. The woodworking analogy of ‘measure twice, cut once’ applies.
•Consider the life span of the application (1-year, 2-years, 5-years, etc.) – keep a log of each application.
•Don’t switch from one product to another without fully understanding any potential issues. Not all products are alike – again,consult with the manufacturers.
•Consult with your stone professional as necessary.
•Ask yourself, does the stone need to be treated in the first place?
Make sure you understand the difference between the types of sealers available on the market.
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