There are times when we are asked about a white haze on grout lines. This is a situation we can rectify. The two most common causes are 1) a white crystal-like or powdery substance known as efflorescence or 2) excess sealer.
Efflorescence results from water traveling along a grout line. It carries salt or another mineral, and once it evaporates the deposit remains on the surface. We address such situations with several techniques, but one key is not to use much water, lest efflorescence returns.
Excess sealer will eventually be removed through wear and tear on the grout, but to expedite the process it can be wiped away with a towel saturated with fresh sealer. In difficult situations a special chemical and a rotary floor machine are needed to scrub the surface.