The consuming public gravitates to perfection so the industry tries to fulfill the desire

Original story at Marble Institute of America

Should natural stone be sealed? In some cases it makes perfect 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.

Marble Institute of America Statement of Position on Sealing Natural Stone Countertops

Most granite countertops do not need to be sealed. Before 1995 there were very few quality penetrating sealers on the market and there were very few cases of staining. Both prior to and after the availability of penetrating sealers, no cases of food poisoning, radon, or food preparation issues associated with treated or untreated granites have been reported. If a homeowner cleans their countertops after each meal, they will rarely, if ever, have staining or clean ability issues with granite. All this being said, many granite countertops receive additional benefit from being sealed. That benefit is the further reduction of moisture migration into an already moisture resistant surface.

Should natural stone counters be sealed? In many cases it makes sense to seal marble and granite countertops with a quality sealer. The product should have a life expectancy of ten to fifteen years and be of an oliophobic (resistant to water and oil based stains) nature. Once properly sealed, the stone will be more resistant against everyday dirt and spills.

In today’s natural stone industry, many species of granite receive a resin treatment at the factory where the blocks of granite are cut into slabs and then polished. The treatment is used to fill micro fissures, indentations and other minor characteristics that are found in many natural stones. The reason for the resin treatment is to address what most consumers consider as imperfections, but in reality are “birth marks”. The consuming public gravitates to perfection, defined as no “birth marks,” and so the marble and granite industry tries to fulfill the desire.
Both resined as well as unresined slabs will outlast most of our lifetimes. Granite should, and in most cases will, be the last countertop surface a person will buy, providing a strong return on investment. The bottom line: Sealing resin treated countertops may increase the resistance of the already resistant nature of stone (adopted 11/8/06).

Dimension Stone Design Manual, Version VII, page 3-5, 3-6

Factors to consider prior to determining if the stone should be protected:

• What are 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 the stone is located (e.g. countertop, floor, wall, foyer, bathroom, etc)? Residential or Commercial?
• What type of maintenance program has or will the stone been subjected to?

The type of stone, its finish, its location, and how it is maintained all need to be considered when determining how to protect the stone. The MIA recommends that these factors be reviewed with the end-user during the decision making process.

Different types of Products

Make sure you understand the differences between the common product types available on the market. The products typically fall into two major categories: Topical Sealer/Coatings and Impregnators.

Topical Sealers are coatings (film formers) designed to protect the surface of stone against water, oil, and other contaminants. They are formulated from natural wax, acrylic, and other plastic compounds. Coatings are classified into two general types: strippable and permanent:

Strippable coatings are formulated to be easily stripped or removed from the stone. These coatings are made of polymers such as acrylics, styrene, and polyethylene, and are usually water-based. Many of the janitorial coatings available on the market are water-based, polymer-type products designed for resilient tile floors and not for stone. Read the label carefully and/or consult with the Manufacturer prior to application.

Permanent coatings, once applied, are very difficult to remove. They’re made of solvent-based or water-based polymers such as polyurethane and epoxies. These are not normally recommended for stone.

When a topical sealer is applied, the maintenance program often shifts from a program focused on the stone care to a program focused on the maintenance of the sealer (for example: stripping and reapplication).