To exclude dampness, use the following: 3/4 lb. mottled soap is dissolved in 1 gall, boiling water, and the hot solution spread steadily with a flat brush over the outer surface of the brickwork, care being taken that it does not lather; this is allowed to dry for twenty-four hours, when a solution, formed of 1/4 lb. alum dissolved in 2 galls. water, is applied in a similar manner over the coating of soap The soap and alum form an insoluble varnish, which the rain is unable to penetrate, and this cause of dampness is thus said to be effectually removed. The operation should be performed in dry, settled weather.

Another method is to use 8 parts linseed oil and 1 part sulphur, heated together to 278°, in an iron vessel.