GRANITE COUNTERTOPS: Care and Maintenance
Granite is a porous stone and the degree of porosity varies depending upon the exact mineral make up of the particular granite you have selected. However, being porous does not mean that you should be unduly concerned with bacteria growth. Bacteria require several things in order to thrive and grow: oxygen, water, sunlight, nutrients, and a substrate to form on. The minerals in granite are toxic to bacteria. As a result, there is no habitable environment for the bacteria to live and grow on a granite surface.

Since granite is porous there are special surface treatments available to make the surface less permeable to water and oils. This surface treatment is called a "sealer." There are two types of sealers, topical and penetrating. Wolde Flooring recommends the penetrating sealer for granite countertops. Topical treatments work better on Marble or Travertine, stones that need more surface protection against scratching.

Topical treatments are available in either a strippable water base or a permanent oil base. Both types are designed to sit on the very top surface of the granite and seal it against water or oil penetration. Topical treatments may make the surface of the stone darker in appearance. The topical sealer will also make the surface appear to have a higher gloss and it can be buffed. To reapply the sealer, the old sealer would have to be removed causing more effort and time to do the job. The permanent topical sealer is more problematic to remove since it is designed to be permanent but may not be depending upon use. Follow the directions of the manufacturer to remove the sealer. Since the topical sealer sits on top of the stone it prevents the stone from breathing so it is possible to trap moisture in the stone. If you select a topical sealer for granite make certain that the manufacturer recommends its use on granite.

Wolde Flooring recommends a penetrating sealer that is either water or oil based and designed to be used on granite. This type sealer will penetrate the stone and reside a few millimeters below the surface in the intercrystalline boundary areas of the stone. These products do not actually "seal" the stone and are more correctly referred to as a repellent rather than a sealer. But they are commonly referred to as sealers and they do create a hydrophobic (water repellent) and oilophobic (oil repellent) barrier but this barrier is air permeable since it is not truly a sealer thus allowing the stone to breathe. There is a preference for the oil based due to its ability to penetrate deeper into the stone than the water based. But there is also an environmental consideration; the water-based products are friendlier to the environment. Either will do the job. There is no need to remove the old sealant when applying a new coating. Make certain that the sealer you select is water and oil repellent and not just "resistant." Silicone, fluoropolymers and siloxane are commonly used in penetrating sealants. Silicone and siloxane work well in repelling water while the fluoropolymers work well in repelling oil based liquids.

Granite is a very durable stone and for the most part is carefree, but as a natural product there are some helpful suggestions that will keep your granite looking like the day it was installed.

Do not use any type of cleanser since the abrasives in the cleanser over time will remove the final polish from the stone making appear dull. Other items that could be detrimental to any stone's surface are citric acids, oils, wine and ink. The effect is not permanent in granite but could be in other types of stone such as marble or travertine since they are calcium carbonate based.

For application follow the directions of the manufacturer.

The applications are all similar and fairly simple generally recommending three steps:

1. Apply with a dry clean cloth spreading evenly over the surface
2. Remove any excess sealant from the surface
3. After the recommended period of drying time wipe the surface with a clean dry cloth.

The question you probably have is when should the sealer be applied? Premier Surface's technicians will seal the stone when it is installed. When should you seal it again? If you prefer a time-based criteria then our standard recommendation is to seal it twice a year, actually it probably needs it only once per year but by saying twice there's a better chance of getting it done once. If you prefer a performance based indicator for when you need sealer just place a few drops of water on a part of the countertop that is exposed to a lot of use. If the drops penetrate the surface within five minutes this is an indicator that the surface should be resealed.

When searching for a sealer product Premier Surface's recommendation is to look on the label to make certain that it is for use on granite, it is an impregnator type and it is safe to use in food preparation areas. 

Remember that this sealer is to stop various types of liquids from penetrating into the stone. Liquids that penetrate the surface can cause spots and stains. However, the stains, if they occur can be removed. The primary issue in removing stains is to know what type of liquid or material caused the stain.

Removing Stains

Here are a few helpful hints in removing stains from granite

The first step is to try the simple method, if that doesn't work then please refer to the section on poultices.

1. Oil based stains (cooking oil, cosmetics, grease, tar)

• An oil based stain will darken the stone and normally must be chemically dissolved so the source of the stain can be flushed and rinsed away. Clean gently with a soft liquid cleanser, household detergent, ammonia, mineral spirits or acetone.

2. Organic Stains (coffee, tea, fruit, tobacco, food)

• May cause a pinkish-brown stain and may disappear after the source of the stain has been removed. Clean with 12% hydrogen peroxide.

3. Ink Stains (magic marker, pen, ink)

• Clean light-colored stones with bleach or hydrogen peroxide. Clean darker stones with acetone or lacquer thinner.

4. Paint Stains

• Small amounts can be removed with lacquer thinner or scraped off carefully with a razor blade. Heavy paint coverage should be removed with a commercial liquid paint stripper. DO NOT USE ACIDS OR FLAME TOOLS TO STRIP PAINT FROM STONE.

Poultices for Stain Removal

In the event that the stain is not cleared with the above actions then it may be necessary to use a poultice type of treatment. A poultice is a warm moist substance placed on the stained area to draw out the causal factors in the stain it is composed of a mixture of chemicals combined with an absorbent material formed into a thick paste. The poultice is spread over the area to a thickness between ¼ and ½ inch using a wood or plastic spatula. The poultice is then covered by plastic and left in place between 24 and 48 hours. As the chemicals dry they will pull out the stain into the absorbent material. The application may have to be repeated to thoroughly remove the stain. Poultice materials include kaolin, fuller's earth (an absorbent clay), whiting, diatomaceous earth, powdered chalk, white molding plaster, and talc. Approximately one pound of prepared poultice will cover one square foot. Do not use whiting or iron type clays such as fuller's earth with acid chemicals; the reaction will cancel the effect of the poultice. A poultice can also be prepared using white cotton balls, plain white paper towels, or gauze pads. Premixed poultices are also available. 

Poultice Mixtures for Various Stains

1. Oil-based Stains

• Poultice with baking soda and water or one of the powdered poultice materials and mineral spirits or a commercial degreaser.

2. Organic Stains

• Poultice with one of the powdered poultice materials and 12% hydrogen peroxide solution, or use acetone instead of hydrogen peroxide.

3. Paint Stains (water-based)

• Poultice with one of the powdered poultice materials and a commercial paint remover.

4. Paint Stains (oil-based)

• Poultice with one of the powdered poultice materials and mineral spirits. Deep stains may require methylene chloride.

5. Ink Stains

• Poultice with one of the powdered poultice material and mineral spirits or methylene chloride.

6. Biological Stains

• Poultice with one of the poultice materials and dilute ammonia or bleach or hydrogen peroxide. WARNING: DO NOT MIX AMMONIA AND BLEACH! THIS COMBINATION CREATES A TOXIC GAS!

7. Copper and Iron Stains

• It is best to consult a professional, as special treatments such as buffing may be required.

 

Applying the Poultice

• If using a powdered poultice material, mix with the cleaning agent or chemical to a thick, creamy consistency. If using paper cotton or gauze soak in the chemical and let drain. Don't let the liquid drip.
• Wet the stain area with distilled water.
• Apply the poultice to the stained area about ¼ to1/2 inch thick extending the poultice beyond the stain area by one inch in all directions. Use a wood or plastic scraper to spread the poultice evenly.
• Cover the poultice with plastic and tape the edges to seal it. Punch several small holes in the plastic to allow vapor to escape.
• Allow the poultice to dry thoroughly, usually 48 hours. The drying process draws the stain out of the stone and into the poultice material. Remove the plastic after 24 hours and allow the poultice to continue drying until it is thoroughly dry.
• Remove the poultice from the stain. Rinse with distilled water and buff dry with a clean soft cloth.