Schluter® FAST-SET Rapid Setting Mortar WHITEFAST SET is Schluter's rapid setting modified thin set mortar it does the same job as ALL SET but cures much faster. In practical terms, you can grout 4 hours after setting tile (vs. overnight with standard mortars). That makes it the go to for time sensitive jobs: rental turnovers, one day bathroom remodels, commercial projects where downtime costs money. Like ALL SET, it's specifically formulated to work with Schluter membranes and substrates. It