Lime Bloom is a crystalline or powdery deposit that forms on the surface of cement based products and brickwork. It is normally white in colour. Efflorescence occurs when soluble salts in the concrete, mortar, render or brickwork come into contact with the atmosphere. As the construction dries out, water dissolves the soluble salts, carrying them in solution to the surface where they are deposited when the water evaporates. It tends to form predominantly in cold, damp conditions. Although efflorescence is unsightly, it is not usually harmful to the concrete or masonry and can normally be removed by stiff brushing or in severe cases a mild brick cleaning acid.