This Smartseal Natural Stone 'Dry Finish' Sealer is an effective impregnating sealer which can be used on a range of hard surfaces, including but not limited to sandstone, granite, limestone, Indian sandstone and slate. The product leaves a totally dry finish which is touch dry in 2 - 3 hours, and waterproof in 24 hours. The chemical structure is altered of the porous stone which will provide not only a superb water repellence but also a stain-resistant surface. You can expect a lifespan of up to 5 years with this product which will protect you against a range of green growth like moss, algae and lichen spores. PLEASE NOTE: Do NOT attempt to use the product in damp conditions. Otherwise, run the risk of getting a moisture reaction. Temperatures must between 13°C and no higher than 23°C If stone been previously sealed, please use a sample on a test area to ensure compatibility. Depending on the stone/surface, more than one coat may be required.