Efflorescence ​

Is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or occasionally in another solvent. The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.
 
In tiling terms, efflorescence is a crystallization of minerals that can commonly appear on the surface of cement grout joints and then spread or leak to the surface of surrounding tiles or surface areas. The term ‘efflorescence’ actually dates back hundreds of years to the Latin word efflorescere, which means to blossom or flower out. It is described like this because the salt crystal are carried upward to the surface through grout joints.
 
Efflorescence will commonly occur when the salt crystals in cement grout joints or adhesive are carried upwards by moisture. As the moisture evaporates when it reaches the surface, it can leave behind the salt deposits which will give the appearance of chalk, white haze on the surrounding surface. In the same way that your body sweats and water evaporates from your skin and leaves a salty residue, cement grout does the same. The darker the grout and the tile, then the more noticeable efflorescence will be.

What are the causes of grout efflorescence?

1. Too much water was used when grouting or mixing adhesive.
2. Grouting was conducted too soon after the tiles are installed.
3. The concrete substrate/slab was not allowed enough time to cure or had a moisture vapour issue.
4. Water used for mixing adhesive or grout was high in chlorine or other mineral contents often added by councils to ensure clean drinking water.
5. The temperature was too cold or suddenly dropped while grout joints were curing.
6. The Sponge used to clean the grout joints and surface grout residue was too wet.
7. The grout joints were wiped excessively during initial clean up.
8. Water residues were left in the groint joints before and whilst grouting.​  ​

How can you prevent grout efflorescence?​

1. Mix the contents of a bag of grout all at once. This allows you to accurately measure the quantity of water required for grout to avoid excessive moisture.
2. Allow the grout and adhesive adequate time to cure. Remember that cooler temperatures will require longer drying times.
3. Perform a calcium chloride test or relative humidity moisture probe test to ensure that concrete slabs are ready to receive tile installation. If required, consider using a waterproofing solution before applying any adhesive.
4. Do not install grout at temperatures below 10 degrees Celsius.
5. While cleaning grout ensure that the sponge is well wring out. Wet sponges and excessive cleaning will cause the grout joints to become saturated.

How to clean/remove efflorescence from tiles and grout?

1. First attempt using natural water and a stiff nylon brush to scrub the efflorescence out. Make sure you avoid soaking the area with more water.
2. If you have an excessive amount of efflorescence, consider using a grout haze remover which you can obtain from your local tile store.
3. If you have efflorescence that may require more serious cleaning and that has allowed time to set in, then consider using a phosphoric acid based heavy duty tile and grout cleaner. Please ensure that you follow the manufacturer’s instructions very carefully as some acidic cleaners can damage the surface of tiles, grout and other materials if instructions are not followed.