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.
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.)
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 resined1, 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.
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 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,” “high solids,” “high speed,” “acrylic,” “thermoplastic,” etc. When in doubt, ask. There are hundreds of different formulas of strippable floor coatings.
Most of them are designed for resilient tile floors and not for stone. If a coating is to be used, be sure it is specified for stone.
Permanent coatings are coatings that are very difficult to remove. They are made of solvent based polymers such as polyurethane, epoxies, etc. These are not recommended for stone.
Impregnators (Penetrating) Sealers
Impregnators are designed to penetrate below the surface of the stone and deposit solid particles in the pores of the stone or to coat the individual minerals below the surface of the stone. Water, oil and dirt are restricted from entering the stone.
Impregnators can be solvent or water based and usually contain silicone, siloxane, silane, methyl silicate or other similar silicon derivatives. The latest impregnators now contain fluoropolymers2.
Impregnators may also be classified as Oleophobic /Lyophoic (oil repelling) or Hydrophobic (water repelling).
Hydrophobic impregnators are designed to repel only water and water-based chemicals. Fruit drinks, coffee, tea, soda, etc. would be repelled by a hydrophobic impregnator.
1 Infused with resins at the factory to increase strenght and density.
2 Fluorocarbons are also lipophobic and oleophobic.
3 Lipophobicity, also sometimes called lipophobia (from the Greek λιποφοβία from λίπος lipos “fat” and φόβος phobos “fear”), is a chemical property of chemical compounds which means “fat rejection”, literally “fear of fat”. Lipophobic compounds are those not soluble in lipids or other non-polar solvents. From the other point of view, they do not absorb fats.
“Oleophobic” (from the Latin oleum “oil”, Greek ελαιοφοβικό eleophobico from έλαιο eleo “oil” and φόβος phobos “fear”) refers to the physical property of a molecule that is repelled from oil.
The most common lipophobic/oleophobic substance is water.
Oleophobic impregnators are designed to repel water and oil based liquids. Cooking oil, grease, body oils, etc. would be repelled by an oleophobic impregnator.
An oleophobic impregnator will always be hydrophobic, but a hydrophobic impregnator may not be oleophobic. Be sure to read product labels carefully to determine if they it is limited to being only hydrophobic. Some products are listed as oil resistant. Oil resistant and oil repellant are entirely different. Oil resistant will only slow down the absorption of oil into the stone. Oil repellant will prevent oil from entering the stone. Again, read product labels carefully. Be sure you are buying the right product for your particular situation.
NOTE —- Impregnators with Fluoropolymers are both oleophobic and hydrophobic.
IMPORTANT: Impregnators will do nothing to protect acid-sensitive stones from etching. They are designed to penetrate the stone’s surface to create a shield to protect staining agents from penetrating below the surface of the stone. Etching occurs on the surface of the stone.
COATING OR IMPREGNATOR?
How do you make the determination between a coating or an impregnator? They both have their advantages and their disadvantages. The following summary should be considered carefully when choosing the proper product:
Coatings – Advantages
Coatings are sealers that place a protective, sacrificial layer on the surface of the stone.
Impregnators – Disadvantages
Sealing: Do it Yourself or call in a PRO?
SEALING: DIY or Call in a Pro?
Is sealing a job for the homeowner, or should you hire a qualified professional to do it for you? Consider the following pros and cons.
The obvious pro for doing it yourself is you save on labor costs. However, if it is not done correctly it could result in problems.
For example, the surface must be thoroughly and completely cleaned. If not, you take the chance of sealing in dirt and debris. Also, keep in mind that the sealer is intended to fill the pores and coat the exposed minerals in the stone, not to coat the surface. If residual sealer is not completely removed from the surface of stone, it may cause problems, including a haze on the stone’s surface that may develop as the sealer dries. Once it has dried completely, sealer can be very difficult to remove, often requiring professional assistance.
Different sealers perform differently in different environments and on different stones. Hiring a pro to do the job may end up saving you in the end. A pro will know which is the best sealer for the job and will use equipment and techniques that allow them to get the job done efficiently.