Grout efflorescence is the whitish haze left on tiles after installation. It generally doesn't come off with the initial cleaning of the tiles immediately following installation. Grout efflorescence occurs when salts in the grout leach through to the surface of the tile. Although efflorescence can be removed from the tiles, you should wait at least three days after installation before applying water, and at least 10 days before applying any products containing acid. This will give the grout ample time to cure. You can effectively remove grout efflorescence from tile by using the proper methods and products.
Use distilled white vinegar to remove mild grout haze. Apply undiluted vinegar to the tile with a rag and wipe the efflorescence from the tile. Follow this by cleaning the tiles with soapy water and drying thoroughly with a clean towel.
Mix the sulphamic acid crystals into a bucket with 4.5 litres (1 gallon) of hot water for tougher grout efflorescence. Sulphamic acid is a product that is readily available at most home improvement centres.
Use a clean sponge to soak the affected area with plain water. Allow the plain water to sit on the tile for about an hour.
Use dry towels to soak up the water from the tile. Pour the acid solution on to the tile so that it forms puddles in the joints.
Scrub the tile with a stiff nylon brush. Let the acid solution sit on the surface for about 5 minutes, then scrub the tile again.
Wipe up the acid solution with rags dipped in clean water. Dry the tile thoroughly with a clean towel.
Apply a cleaner specific to the type of tile you are working with or a grout haze removal product. Follow the manufacturer's specific instructions for application.
Substitute phosphoric acid for sulphamic acid if the grout efflorescence is really bad. Phosphoric acid is a stronger chemical than sulphamic acid and will be effective at removing more troublesome cases of grout efflorescence. Mix one part phosphoric acid into a bucket with five parts plain water. Apply and clean up the solution in the same manner used with the sulphamic acid. Follow up by cleaning the tiles with an appropriate tile cleaner for the specific tile you are working with.
Wear rubber gloves, protective eyewear and long sleeves and trousers when working with products containing acid. These chemicals can cause serious injury to your body.
Never apply acid to the tile without wetting it first. The tile may sustain burns from the acid if it is not wetted prior to application.
Test the product you are using on a small inconspicuous area of the tile before applying it throughout. Look for any discolouration or damage the product may cause to the tile.