I have a concrete wall that builds up heavy efflorescence in the spring. There doesn't seem to be any other source of efflorescence except the wall itself, but I have cleaned it two years in a row and the white deposit still keeps coming back. How can I stop it?
Spring rains are undoubtedly soaking your wall and picking up a load of lime or other soluble material from within the wall. The water slowly migrates back to the outer surface, where it deposits the crystals as it evaporates. This process probably will continue as long as there is soluble material left in the wall. One way to overcome the problem is to repeat the process purposely, but to arrange to have the efflorescence deposited outside the wall, not on its surface. To do this you saturate the wall from the outside with water and immediately plaster on a thick layer of papier-mache made of chewed-up newspaper, wet enough to stick to the wall.When the wall has dried the efflorescence will be in the papier-mache, which can be peeled off. It may be necessary to use two or three repetitions. This technique was suggested some years ago by the observation that farmers never had any efflorescence on barns at the place where the manure pile lay against the wall. One farmer even plastered the manure on generally, like the papier-mache, and got rid of all the efflorescence.