Dissolve l lb. of yellow soap in a gallon of warm water; also dissolve l lb. off alum in a gallon of warm water. Dip the millboard for a few seconds in the soap solution, and directly afterwards into the alum bath, and then allow to dry. Another method of applying the waterproof solution is to add the alum solution to the soap solution, collect the precipitate on a piece of muslin and dry it, then place it in a bottle and add a little benzoline; the alumina soap will gradually dissolve in this, and may be thinned with more benzoline so that it can be applied to the millboard with a brush.