I

A good and simple remedy to obviate this evil is caoutchouc glue, which is prepared from rubber hose. The walls to be laid dry are first to be thoroughly cleaned by brushing and rubbing off; then the caoutchouc size, which has been previously made liquid by heating, is applied with a broad brush in a uniform layer—about 8 to 12 inches higher than the wall appears damp — and finally paper is pasted over the glue when the latter is still sticky. The paper will at once adhere very firmly. Or else, apply the liquefied glue in a uniform layer upon paper (wall paper, caoutchouc paper, etc.). Upon this, size paint may be applied, or it may be covered with wall paper or plaster.

If the caoutchouc size is put on with the necessary care—i. e., if all damp spots are covered with it—the wall is laid dry for the future, and no peeling off of the paint or the wall paper needs to be apprehended. In cellars, protection from dampness can be had in a like manner, as the caoutchouc glue adheres equally well to all surfaces, whether stone, glass, metal, or wood.

II

The walls must be well cleaned before painting. If the plaster should be worn and permeated with saltpeter in places it should be renewed and smoothed. These clean surfaces are coated twice with a water-glass solution, 1.1, using a brush and allowed to dry well. Then they are painted 3 times with the following mixture: Dissolve 100 parts, by weight, of mastic in 10 parts of absolute alcohol; pour 1,000 parts of water over 200 parts of isinglass; allow to soak for 6 hours; heat to solution and add 100 parts of alcohol (50 per cent). Into this mixture pour a hot solution of 50 parts of ammonia in 250 parts of alcohol (50 per cent), stir well, and subsequently add the mastic solution and stand aside warm, stirring diligently. After 5 minutes take away from the fire and painting may be commenced. Before a fresh application, however, the solution should be removed.

When this coating has dried completely it is covered with oil or varnish paint, preferably the latter. In the same manner the exudation of so-called saltpeter in fresh masonry or on the exterior of facades, etc., may be prevented, size paint or lime paint being employed instead of the oil-varnish paint. New walls which are to be painted will give off no more saltpeter after 2 or 3 applications of the isinglass solution, so that the colors of the wall paper will not be injured either. Stains caused by smoke, soot, etc., on ceilings of rooms, kitchens, or corridors which are difficult to cover up with size paint, may also be completely isolated by applying the warm isinglass solution 2 or 3 times. The size paint is, of course, put on only after complete drying of the ceilings.