Why canít you grout the floor right away?
A grout job with even color that matches the desired standard is sought each time tile is set. Many factors influence the appearance of the grout including ambient temperature, humidity, quantity of mixing water, clean-up procedure and time allowed before grouting.
All of the factors mentioned have an impact on the final appearance of the grout. Some of them are not under the control of the installer, but one that the installer can control (and one that can cause some of the biggest grout problems if not followed), is to allow adequate time before grouting. Hereís why:
The setting material used to set the tile has water in it. Whether the water comes from a water-based adhesive (mastic or glue) or from thin-set mixed with water, the water must be allowed to evaporate or be absorbed into the substrate (concrete floor) before grouting begins. The water in the setting material will act as a carrier for the pigments and whatever else it can dissolve before evaporating at the grout surface. The effect is most often an uneven color. In other cases, the color may be yellowed because the substances in water-based mastic adhesives may be carried with the evaporating water. Allowing the water-based adhesives to dry properly before grouting eliminates the chance of these substances from being carried to the surface.
In order to avoid the problems associated with grouting too early, one must allow the setting material to dry. For most products, this takes about 24 hours. If grouting must be accomplished faster than 24 hours, a fast setting mortar can be used at a greater expense. These products usually allow grouting in 3 to 6 hours from installation.
John Kehoe, TEC Technical Manager
TEC Incorporated, 315 S. Hicks Rd, Palatine, IL