What is that white stuff? – Grout Efflorescence

Have you ever seen discolored grout after you finished your tile installation? That discoloration may be something called “efflorescence.” Efflorescence is a whitish crystalline or powdery deposit on grout lines and tile surfaces that can mar even the best looking grout-tile combinations. It will turn grout from an accent to eyesore. Luckily, grout efflorescence can be removed, and even prevented with proper tile installation technique.

Grout Efflorescence

How to prevent efflorescence
Grout contains Portland cement. Efflorescence can occur in any Portland cement product. It occurs when water-soluble minerals dissolve and migrate to the installation surface.  You can interrupt this process and help prevent efflorescence. 

1. Keep Out Moisture: Waterproof membranes installed close to the installation surface can help prevent grout efflorescence. Tile can be bonded directly to the membrane, which will work to deflect water from the installation and prevent its absorption into the substrate. Products like these are especially important in wet areas like showers, spas, pools, hot tubs and fountains. It is always best to confirm that your membrane, tile, mortar and grout are compatible, and make sure your installation is capped and has the correct flashing as necessary.

Also consider using a penetrating sealer on your installation. Penetrating sealers can form a water-resistant shield over your installation without changing its appearance. Just be sure the grout is cured, prior to sealing the installation.

2. Choose the Right Products:  Look for high performance tile setting products with lower absorption rates.  It should be noted that even the best quality mortars require proper coverage. Incomplete coverage can allow water to enter the system, ultimately leading to efflorescence.

Some grouts are specifically designed to deliver color consistency and reduce the risk of efflorescence. Look for grout that exceeds ANSI A118.7 when efflorescence is a concern.

Removing Efflorescence
If you think you see efflorescence, there are a few simple tests that can confirm your suspicions. Efflorescence will turn into a powder when pinched between fingers and will dissolve in water. If you positively identify efflorescence, you can take the following steps to remove it:

1. Dry Brush: If you notice the efflorescence soon after it appears, you may be able to remove it simply by scrubbing the grout gently with a stiff nylon brush.

2. Use a Mild Acid: If water alone does not do the trick, try using a mild acid to remove efflorescence. Products with sulfamic or phosphoric acid can be used effectively, but stronger acids can burn fixtures and tile. Be absolutely sure that when using an acid to dilute it.  A 1 part acid to 10 part water for example. If you do not have an acidic cleaner on hand, you can create your own by mixing 1 part vinegar with 1 part water. Be sure the grout has cured 10 days and wear gloves when treating efflorescence with an acid. Apply it with a sponge or brush. If your problem is truly efflorescence, it should react to the acid immediately.


Make sure you rinse the installation surface with clean water once grout efflorescence removal is complete, and use acid cleaners sparingly. Acidic cleaners should not be used on marble, limestone and travertine. Check with manufacturer of your tile to make sure an acidic cleaner will not alter your installation’s appearance.

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