Marble is a fairly porous natural stone material that readily absorbs moisture, which means that it can be stained quite easily. But protecting marble against moisture intrusion, as well as against stains, is relatively easy if you seal it when you install it as well as every year or so after that. The frequency of sealing will depend on how much traffic a marble floor gets.
The process for sealing a marble floor is relatively easy and should take less than an hour with each application. Unlike a ceramic or porcelain tile floor, it's not just the grout lines where sealing is critical, but the entire surface. The same process used to seal marble floors can also be used to keep a marble countertop sealed against stains.
Equipment / Tools
- Foam brush
- pH-neutral cleaner for marble
- Marble sealer
- Clean rag
Test the Seal Coat
To test the surface to see if it requires a fresh coat of sealer, place a teaspoon of water on the surface and let it sit for about 20 minutes. Blot up the water with a paper towel and examine the surface. If the water has been absorbed, it will leave a dark mark on the surface, indicating that the marble needs to be resealed.
Clean the Floor
Before sealing your marble floor, thoroughly clean it with a pH-neutral cleaner made for marble. Do not use cleaners containing acid (including vinegar), which can etch the stone. Let the floor dry completely.
Test the Marble Sealer
Test a small amount of the marble sealer in an inconspicuous area to make sure the sealant will not discolor the stone. Allow the sealer in the test area to dry thoroughly, then compare its appearance to the other tiles. The only difference should be that the sealed surface is slightly glossier than the other areas. If the sealer creates dramatic color differences, you should try another type of sealer.
Apply Marble Sealer
Apply the sealer to each tile individually, using a foam brush or soft cloth dipped in the sealer. The goal is to create a very thin layer that evaporates in a matter of minutes. Do not allow the sealer to puddle. If bubbles do form, smooth them out with the front edge of the brush.
Follow the sealer label instructions regarding the method of application—some prefer foam brush application, others suggest using a cloth. Still others are sprayed on.
Seal the Grout Joints
Brush marble sealer onto the grout joints as you complete each small section of tiles. Dip the foam brush lightly into the marble sealer, then run the thin edge of the brush along each of the grout lines. Use the broad edge of the brush to wipe up any excess. The grout joints are especially susceptible to staining, so it is important that they get coated thoroughly. Let the sealer dry completely—this usually takes two to four hours.
Apply Second Coat
When the sealer is completely dry, repeat the application to the marble and the grout joints. You can walk on the floor within a few hours, but wait until the sealer has fully cured—48 to 72 hours—before resuming normal cleaning of the floor. You should also keep any potentially staining materials (stain agents) out of the area until the sealer has fully cured.