Smartseal black limestone sealer is a highly-effective solvent-based sealer and re-colourant for black limestone which gives a transformative effect. Limestone slabs will often fade over time and gradually turn a lighter shade of grey. The black limestone sealer can transform the look of faded limestone patios and make them look like they were recently laid. The sealer can be re-applied at any time to ensure any limestone slabs on patios or other external surfaces look good at all times. Technical Preparation: Clean surface using a pressure washer and/or Patio Clean Xtreme. Allow to dry for a minimum of 72 hours Apply above 12°C with a temperature no higher than 23°C Two coats are recommended Apply by roller Coverage: Average coverage approx. 4 - 5m²/litre first coat (dependant on surface) and approx.