This is a great question. The answer is, it depends on the product you are using to seal the grout. Grout Sealers that have a really heavy mixture of Fluoropolymers will leave a residual like haze on the grout if the Grout is not totally dry. Some cleaning companies will use a solvent product to seal the grout while wet, this is a great way to apply a sealer as the solvents do a great job of penetrating through the moisture barrier.
A grout cleaning and sealing service can clean and seal the same day. Grout can be sealed immediately after the cleaning whether wet or dry if you use the right product.
For A FREE In Home Estimate For Tile and Grout Cleaning and Sealing give us a call at (832)303-3546. Check Out Our Tile and Grout Cleaning Process Here.