CeramicTilePro GRB-CTP-4 Grout Bond Re-grouting Additive Works Better Than Sealing - Used For Re-Grouting Sanded and Non-Sanded Grout Bonds New Grout to Old - 60 Minute Working Time! Excellent For Wet Areas - Makes Grout Stronger Helps to Waterproof Grout Mix with Any Color Cement Based Grout