Porter's Salt Check inhibits efflorescence, a whitish salty powder, crust or crystal formed on the surface of a mortar or masonry that is subject to excess moisture. Salt Check is a water thinnable solvent-free emulsion that serves as a high quality general purpose water repellent for impregnating and priming mineral surfaces such as cement render, bricks, concrete, sandstone and mineral plasters. This product contains 0g/L VOC. The APAS target level for this product is 80g/L. (APAS is the Australian Paint Approval Scheme).