Natural Stone Care – Marble and Granite
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 by water and oils. This surface treatment is called a “sealer.” There are two types of sealers, topical and penetrating. Premier Surfaces 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.
Premier Surfaces 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 millimetres 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 repellant 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 repellant 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.
For application follow the directions of the manufacturer.The applications are all similar and fairly simple generally recommending three steps:
- Apply with a dry clean cloth spreading evenly over the surface
- Remove any excess sealant from the surface
- 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.
- 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.
- 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 and a few drops of ammonia.
- Ink Stains (magic marker, pen, ink)
Clean light-coloured stones with bleach or hydrogen peroxide. Clean darker stones with acetone or lacquer thinner.
- 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 for 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.
Maintenance of Your Granite Countertops
Protect your countertops by never permitting anyone to stand on them. The weakest area and most susceptible to cracks is the area in front of sink and cook top cut outs. Premier Surfaces adds reinforcing steel rods to these areas to improve the strength. However, it is a good practice to use a stepladder and not the countertop to reach high cabinets or light fixtures.
As a matter of safety do not place hot pans on the granite countertop. The heat will not bother the granite but there have been instances where people place hands on the area where a hot pan was just removed from the granite causing burns.
The edges of the granite are most susceptible to chipping. Just use extra care when working with utensils near the edges. Chips can be fixed, if they occur give us a call.
Final Note:
It is worth repeating! The only thing needed to keep the surface of your granite countertop clean on a daily basis is dishwashing soap, rinsed with clean water and wiped dry with a clean dry cloth. Also, if you would not use a cleaner on your hands, don’t use it on your countertops |
