Lime bloom
Where general lightening or patchiness on coloured cement products, that are otherwise sound and fully cured, seems to disappear when dampened with water, this is an indicator that the material has been affected by lime bloom. Lime bloom does not result from a fault in the product but rather from the intolerance of cement to certain conditions during its early stage of hydration. BS 5262 Code of practice for external renderings clauses 34.1 and 47 confirm that lime bloom is a phenomenon that sometimes affects cement products. This occurs more often when these products are subjected to damp conditions, and or low temperatures during early curing, the resulting thin film of what is basically lime on the surface of the product, does not affect the integrity or strength of the material.