How to avoid problems of exudation and efflorescence in semi-flexible exterior masonry coatings

摘要

The paints are applied in 2 coats of 350g/m~2 by brush (with 24h between coats) to porous clay bricks. After 24h of drying, the bricks are placed in a saturated sait solution for 3 weeks. Changes in film appearance (blisters, salt deposits, cracking, etc.) are obser-ved. The aim of this test method is to simulate the conditions of efflorescence to which the paint film might be exposed during real conditions of use. For the 7 commercial paints, like with most of water borne facade coatings, some significant defects appear after the first few days of test: at the begin-ning a salt deposit due salt water migration through the paint film can be seen, then some blisters and cracking resulting from loss of adhesion under pressure at the film/substrate interface start to appear.