Brick & Patio Cleaner is a fast-acting acid-based formula (9.5% strength) that dissolves mortar and cement stains and ingrained dirt and paint on most mineral surfaces such as brick, stone, concrete, paving flags and earthenware. Please note this product is only suitable for external applications. Acid-based - powerful cleaning action. Water clean up.Economical in use. 1L (neat) will clean up approx. 10m of surface stain.