Sealing Stone over Previous Sealers – Yes You Can
We often get questions something like this:
“I need to re-seal my granite countertops, but I don’t know what sealer (if any) my installer used. Can you help?”
The short answer is usually YES, with the following caveat; make sure the stone does not have a topical sealer first (and read below for another qualifier). This is highly unlikely, as most stone sealers for polished surfaces are ‘impregnating’ sealers, or ‘penetrating’ sealers. The operative word denotes that the sealer is absorbed down into the pores of the stone, rather than laying on the surface.
Some types of stone like tumbled travertine, and natural slate, may often have a topical sealer on the surface. You can usually tell this fairly easily by looking to see if there are scratches on the surface, or if there is any noticeable peeling of the coating. Yellowing is a dead giveaway.
For countertops or floors, I suggest performing the ‘water test’ first. Simply take a tablespoon of water and pour it on the surface, letting it absorb for 20 minutes. After 20 minutes, wipe the area dry with paper towels or an absorbent cloth and notice if there is any visible darkening of the color. If the water was absorbed, it will almost always create a dark spot on the surface of the stone. If this is the case, then it is definitely time to apply a quality impregnating sealer.
Here is where it gets a bit tricky…if you wish to use a water-based impregnator, then you may have limited success. If your water test showed the stone drinking up the water, then no-problem, go ahead and use a water based impregnator. We suggest HMK S232 Water Based Impregnating Sealer. If your water test did show some absorption, but the water pooled on the surface then you may want to use a solvent based impregnator.
Prior to using any impregnator, it is best to perform a Deep Cleaning first to remove all topical polishes, waxes, light grease, and grime from the surface. Please see the following directions: Deep Cleaning of All Natural Stone
For optimal results, we suggest using HMK S234 Silicone Impregnator. This penetrating sealer will drive the protectant molecules deeper into the stone than a water based impregnator, because the solvent molecules are smaller than H2O (water).
In case you are interested to see just how well S234 performs, please see how HMK protected a granite countertop from a red wine spill HERE
Using professional grade impregnating sealers will help protect your stone surfaces, and your investment.
If you have technical questions or have a stain that you cannot remove, please email us HERE