How To Seal A Stone Countertop And Why You Need To Do It

There seems to be a lot of confusion as to whether natural stone should be sealed or not. Although there are some stones that definitely need to be sealed, some countertops installed for use in homes do not. The stone industry tends to apply a blanket approach to all stone advocating sealing all stone and applying sealant often. Part of why granite tops are so desirable is due to their natural uniqueness and individual charm.

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Because no two slabs are the same, it stands to reason that granite slabs will have different absorbency qualities. This in effect will answer the questions of how many applications of sealant needs to be applied and how often. Granite from different parts of the world will display different characteristics even though they may be of the same color. For example, the beautiful green granite from Africa differs greatly in absorbency qualities from green granite found in China.



If a natural stone countertop requires protection due to its high absorbency, this can be done by applying an impregnating liquid that will be absorbed into the stone. A simple test based on nature can be done to ascertain whether a granite slab needs to be sealed or not. Simply pour a small amount of water onto the countertop and let is sit for about 15 minutes before wiping it off. Upon examination you will either find a dark patch where the water has been absorbed, or nothing, in which case the stone will not absorb liquid and a sealant will just be a waste of time.



A further test needs to be done to find out if the stone is susceptible to staining agents. Apply a few drops of mineral oil to the surface and leave it for ten minutes before wiping. A darkened spot will indicate that you need to seal the granite with a solvent-based sealer or impregnator in favor of a water-based product.



If a stone counter top requires a sealant it may need to be reapplied after a time period of between 1 to 15 years, depending on the unique characteristics of the particular stone. This will become apparent when the stone becomes darkened from liquid spills which are an indication that the sealant has worn off. With this information you now have the knowledge to apply a sealant or not and when to re-apply, without guessing.



Although no sealant for granite is a safe and stain-proof solution, a good sealant will allow you the time needed to wipe spills before they are absorbed. Sealing agents for natural stone will not make granite shiny as only polishing can do that.



How To Seal A Stone Counter Top



Before deciding to seal your stone counter top there are three things to do first:



1. Test whether the stone needs sealing from water and from mineral oil. If no dark stains remain, the granite may already have been sealed and only needs to be done again when the sealant wears off in the future.



2. Select a sealant specifically designed for granite with penetrating properties that will slow down the absorption of liquid. A high quality sealant will contain “fluorocarbon aliphatic resin” that will provide good protection for many years, but comes with a high price-tag. Other options include products with “silane” or “siloxane”, with the least durable being silicone or linseed based sealers. Sealants can be water or solvent based which are both adequate, although water based sealants are more environmentally friendly and easier to apply. You can find our review of Granite Gold sealer here.



3. Read the instructions carefully and follow them.




Below is a method that provides more detail than most product labels:



- Thoroughly clean the surface with soap and water or a special stone cleaner and wipe dry with a lint-free cloth. Allow the granite to dry out complete for at least 24 hours. If the counter top is newly installed, wait until there is no dust from construction before sealing as it can interfere with the protection offered by the product.


- Wear gloves and work in a well ventilated area to prevent inhaling harmful vapors from solvent based sealants.


- Test the product on a small area in an unobtrusive corner. If there is a hazy residue or discoloration, use a different product.


- Apply sealer evenly by covering the surface with a fine spray, or use a lint-free cloth dampened with sealant or use a brush. The surface should be damp and not wet or soaked.


- Allow the sealer to be absorbed into the stone according to the instructions on the label, usually about 20 minutes. Leaving it on for too long may cause discoloration of the stone.


- If directed by the instructions on the label, add a second coat before the first coat is entirely dry.


- Wipe the surface with a clean cloth after the allotted time to remove any excess and to prevent causing an unattractive haze.


- Leave the counter to “cure” for approximately 48 hours before use. Although some product instructions may state that it only needs to cure for a couple hours, it is a good idea to allow the stone to dry completely before subjecting it to normal use or liquids.



Protection of the stone can last for up to fifteen years depending on the quality of the sealer used. Never re-apply sealant to a surface without testing whether it is necessary. When spilled water immediately darkens the granite it is an indication that it needs reapplication of a sealer.

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