Are you a little confused about whether or not to seal your natural stone? You’ve done your homework and researched the topic on the web only to find that there are opposing opinions on the topic. Most experts recommend sealing all stone while others emphatically state that not all natural stone needs to be sealed.
STONE ABSORBENCY TEST
To get a general idea of how absorbent the stone is, place several drops of water on the surface of the stone and time how long it takes for the water to completely disappear. If the water disappears in under one minute, consider the stone very porous.
If it takes up to 3-4 minutes, consider it porous. If it takes more than 3-4 minutes, consider it slightly porous. This simple test will also give a good indication of the quantity of sealer needed to protect the entire area.
SO WHAT IS THE ANSWER ?
Let’s make it simple. To be safe, let me say that for the most part, all stone surfaces should be sealed for maximum protection. The worst case when you are dealing with a stone that is not very porous is that the stone will absorb very little sealer to achieve maximized protection. Don’t look the cost of the sealer as a waste of money though. Consider it added peace of mind.
(Tip: see the about testing absorbency first. If your stone is not very absorbent, buy only a very small bottle of sealer.)
Caveats
New Countertops ? Some granite countertops are pre-sealed. Ask your fabricator or perform the Stone Absorbency Test (see sidebar).
Resined Stones: If the stone is resined, it may not need sealing. Perform the absorbency test to be sure.
CHOOSING THE CORRECT SEALER
Many factors need to be considered when choosing the correct sealer.
Stone Type: Many, if not most stones today are resined at the factory. Resining adds strength to more fragile stones thus creating a much larger supply of natural stones that can be used. All stone is not created equal. How porous a stone is and how fast it will absorb a liquid is called the absorption coefficient.
This coefficient is extremely important when choosing a sealer. Granite generally will have a higher absorption coefficient than a polished marble. Limestone can be extremely absorbent. The higher the absorption coefficient, the more difficult it will be to seal the stone adequately.
Stone Finish: The finish on a stone affects its absorption coefficient. A polished surface will be less absorbent than a honed or flamed finish. The above absorption test will determine how absorbent a stone is.
Stone Location: Where is the stone located? Is the stone on the floor, wall, countertop? Is it in a kitchen, foyer, lobby, bathroom? What are they chances of it being subjected to spills or staining agents? Exposure to water, oil, heavy traffic, pets, etc. all need to be taken into consideration when choosing the proper product for protection.
For example, a marble kitchen floor that is used daily will need a sealer that has both oil and water repellant properties. At the other end of that spectrum, dealing with a front foyer may only need a water repellant sealer. When protecting a busy hotel lobby floor, don’t be falsely assured that a wax coating will provide the optimal solution. It may track and scuff too easily, requiring costly upkeep. A quality impregnator and a polishing program may be needed to maintain the shine and protection.
Current Maintenance: How is the stone maintained ? Is it exposed to harsh cleaning chemicals not intended for natural stone? On the other hand, if maintenance is neglected, a stone floor will have ground-in dirt and grit and if it has a high polish it will be worn. In this case, no matter how well it is protected, it will get dirty and dull. For example, a moderately busy hotel lobby floor that gets dust mopped and wet mopped every day may need a good quality impregnator.
On the other hand, a stone foyer floor located in a home and not receiving any traffic does not need daily cleaning. An application of a water repellant impregnator may be all that’s necessary. The type of stone, its finish, its location, and how it is maintained all need to be considered when determining how to protect it. Evaluate each of these parameters carefully. How do we protect stone and other porous materials from staining? There are so many sealers on the market today. Which ones are best? Which ones really work? It can be very confusing trying to choose a sealer to protect stone.
In the past several years the stone restoration and janitorial industries have bombarded the market with hundreds of products to seal, protect and polish stone. Fortunately, all of these products fall into only two major categories:
1) Coatings
2) Impregnators (Penetrating) Sealers
Coatings:
Coatings are sealers that place a sacrificial coating on top of the stone acting as a barrier to prevent water, oil and dirt from entering the pores of the stone.
Coatings can be classified into two general types:
Strippable
1) Permanent
2) Strippable Coatings
Strippable coatings are coatings that are designed to be easily stripped or removed from the surface of the stone. These coatings are made of polymers consisting of acrylics, styrene, polyethylene and others. They are usually water based. Many of the janitorial products are water based polymer type coatings. To identify these coatings look for terms on the label such as “metal cross link.
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