How to Seal Marble and Natural Stone Tile

What a sealer does, and what it doesn't

The Natural Stone Institute points out that most stone "sealers" are really impregnators: they sit inside the stone and act as a repellent rather than forming a seal. The result is more time to wipe up a spill before it soaks in.

A sealer doesn't make stone stain proof, waterproof or maintenance-free. It also doesn't protect against etching. Etching is a dull mark left when an acid, such as citrus, vinegar or wine, reacts with the calcium carbonate in stones like marble and travertine. See Etching vs Staining on Marble.

Does your stone need sealing? The water-drop test

Place a few drops of water on the stone and leave them for about 15 minutes. Then wipe the area dry.

• The stone darkened: water soaked in, and a sealer can help.
• Nothing changed: the stone isn't absorbing much. It may not need a sealer, or an earlier sealer is still working.

Not every stone needs sealing. Repeat the test before resealing rather than resealing on a calendar.

The three kinds of sealer

For most marble and travertine tile, an impregnating sealer is the usual choice. On kitchen floors and near oils, choose an oil- and water-repellent (oleophobic) version.

How to seal marble tile, step by step

These steps are general. The sealer maker's label always comes first.

1. Confirm the sealer is labeled for marble or calcareous stone, and for the location (interior, exterior, shower or floor).
2. Let a new installation cure for the time the grout and setting materials require.
3. Clean the surface with a pH-neutral stone cleaner and let it dry completely.
4. Test the sealer on a spare tile or a hidden corner. Check that it doesn't change the color or sheen in a way you don't want.
5. Apply it evenly, following the label for coverage, ventilation and dwell time.
6. Wipe off the excess before it dries on the surface. Leftover sealer can leave haze or streaks.
7. Let it cure for the time the label gives before walking on it or getting it wet.
8. Repeat the water-drop test afterward to check the result.

How often to reseal

There's no universal schedule. Stone restorers quoted by the Natural Stone Institute's Use Natural Stone site disagree: one suggests every nine months to a year, while another suggests five to ten years. The same article notes some sealers last more than ten years and others only six months. Follow the product label, and reseal when the water-drop test shows the stone absorbing again.

Good to know

• More sealer isn't better. Excess sealer leaves haze and can't sink in.
• Sealed marble still etches. Wipe up acidic spills quickly.
• Keep a few spare tiles from your order. They're useful for testing sealers and cleaners.