Tests of Stone

Soap and Alum.

A cheap and highly effect ive method of making mortar and masonry im pervious to moisture is known as Sylvester's Method. This is more often applied to brick than to stone masonry, but may be used in the mortar in either case. It is also used for water proofing concrete. As described in the Trans actions of the American Society of Civil Engi neers (Vol. I), the Sylvester process consists in using two washes or solutions for covering the surface of the walls—one composed of Castile soap and water, and one of alum and water. The proportions are three-quarters of a pound of soap to one gallon of water, and half a pound of alum to four gallons of water, both substances being perfectly dissolved in the water before being used. The walls should be perfectly clean and dry, and the temperature of the air not above 50 degrees Fahrenheit when the composi tion is applied.

The first coat or soap-wash should be laid on when boiling hot, with a flat brush, taking care not to create a lather on the brickwork. This wash should remain 24 hours, so as to become dry and hard before the second coat or alum wash is applied, which should be put on in the same manner as the first. The temperature of this wash, when applied, may be 60 degrees or 70 degrees Fahrenheit; and this also should re main 24 hours before a second coat of the soap wash is put on. These coats are to be applied alternately until the walls are made impervious to water. The alum and soap thus combined

form an insoluble compound, filling the pores of the masonry, and entirely prevent the water from entering the walls.

While it cannot be said that this method has become very general in use, it is to be recom mended. Instead of being applied as a wash, the alum and soap may be mixed with the cement with good results. The present practice is to mix an amount of alum equal to 1 per cent of the weight of the water with the dry cement. Three times this weight of soap is then dissolved in the water before the latter is applied to the cement. It is better to use greater rather than smaller proportions of the alum and soap than those just stated, although the effect of the mixture is to decrease slightly the tensile strength of the mor tar.

In case aluminum sulphate is used, one part is mixed with the cement, to four parts of hard soap, or rather more of soft soap. In using these preventatives as a wash, it is best to follow the original instructions and apply them while hot.

Not a few other washes have been suggested and tried for the purpose of excluding moisture from walls, but the question of their complete success is still debated. Coats of hot asphalt or tar are often applied to underground foundations or walls, with fairly good results. Sometimes tar felt is imbedded in the concrete of walls and foundations for the same purpose.