Smartseal Roof Tile Sealer is a clear, professional-grade, solvent-free, acrylic impregnating sealer for concrete, clay tile or slate roofs. Once applied, the chemical structure of the tile sealer is altered in order to produce an excellent water repellent surface. The growth of moss, algae and lichens is largely restricted to the surface of the tile after application of the sealer. Use a handheld sprayer or brush for application purposes, apply to saturation, we recommend that after once 20-30 minutes have passed, a light second 'wet on wet' coat is added. If rain is forecasted or temperatures are below 10°C, do NOT attempt to apply the sealer.