G.K.BOWLER* and N.B.WINTER** * Hanson Brick Limited** W.H.D. Microanalysis Consultants Limited

Efflorescence was traditionally regarded as temporary. In the last 15 years or so persistent grey white deposits have been seen comprising syngenite or gypsum. These both occur on a wide range of bricks which have not changed in composition or properties so work was concentrated on changes in the chemistry and composition of the mortar including cement and admixtures. Tests have shown that typical air entraining agents and washing-up liquids often used are associated with the development of gypsum rich deposits on the surface of bricks. Older brickwork in UK is demonstrably free from persistent efflorescence, the appearance of which coincides quite well with the widespread use of organic surfactants in masonry construction.