Simple to apply, wait 6-8 hours on area and no scrubbing required Its fast acting, good to apply on tiles, silicone sealant (around windows, sinks and baths), shower-heads, Pool and more It is gel type, easy to use and effectively acting for a longer time Perfect for tiles ,Silicone Caulk, Sink, Kitchen, Showers, Bathroom Give it a try before striping the caulk off and redo it. SKYLAR LIFE Black spots & Sealant Cleaner, Caulk Whitener, Black Stain Problem Solver, Best for Home Sink,Kitchen,Showers,Bathroom and Floor Tile (2-Pack)