Cleaning Brickwork

CLEANING BRICKWORK Brick walls in cities and factory towns often become discolored by smoke and soot. A periodical cleaning is therefore advisable, and the brickwork can be restored almost to its original freshness by washing it first with a muriatic acid solution in proportions of pint of the acid to each gallon of water for every 100 sq. ft. of surface. When dry, the wall is then brushed down with kerosene oil, and this is followed by a coating of linseed oil. This gives a kind of waterproofing to the wall, and is said to mellow the color of red brick in pleasing fashion. Many other cleaning mixtures are in use, in which liquid ammonia and soap are the chief cleaning factors.

Efflorescence. Efflorescence, often termed is a white scum that appears on the surface of brick walls after they have been soaked with rain or in the presence of marked atmospheric humidity. This scum is due to the presence of soluble salts in the clay or the mortar. In some cases, where the clay is the cause, these white patches appear on the brick when taken from the kihi. The presence of sulphuric acid salts on the brick in the drier had not been noticed; and if the brick are well burned, the scum is welded firmly to the clay, and no amount of washing with the strongest acids will remove it. The scum in this case is easily seen by the purchaser, and the brick need not be bought if discolored brick are objectionable.

The brickmaker can remove the cause of trouble by mixing with the clay carbonate of barytes, which, in changing the soluble salts in the clay, such as sulphate of lime, forms insoluble sulphate of barytes and insoluble carbonate of lime. No soluble matter is left in the material, and consequently no scum will appear at any stage of the manufacturing process or when the brick are in service.

The home-builder, contractor, and architect are vitally interested in learning how to deal successfully with efflorescence which appears after the building is erected and which mars the beauty of the finished structure. If it is present in immediate and general distribut ion a ft or rain or during very damp weather, the scumming is more likely to have come from the mortar than the clay. The water absorbed by the mor

tar, in evaporating deposits the salts of soda, magnesia, potash, etc., which it has dissolved, and leaves an unsightly scum on the wall surface.

The evaporation of water from the brick brings to the surface the soluble salts from the interior in the same way, but the action is not so rapid as in the case of mortar. In some eases, brick themselves free from these salts may show efflorescence by absorption of water impregnated with the salts in the mortar.

Efflorescence disappears gradually ender the action of wind and rains. In the ease of the Monadnock Building, Chicago, in 1902, the efflorescence was marked throughout the sill length of the 15th story. Each year the line of efflorescence dropped until at the time of writing, but few signs of "whitewash" can be noted, and those on the lowest story.

Waiting for efflorescence to disappear, however, is a lengthy operation. A quick way to remove it is by using hydrochloric acid mixed with five times its volume of water. The wall is first thoroughly dampened, then well scrubbed with the acid solution; after scrubbing, the wall should be washed perfectly clean with clear water. Nitric acid is also used for this purpose.

Further effloresTnce may be stopped by using a waterproofing compound on the wall. The Sylvester process is one of the best known, and its effect is produced by alum and soap solutions. The alum solution is made in proportion of 1 lb. of alum to one gallon of water. The soap solution is composed of 2.2 lbs. of good soap dissolved in each gallon of water. The wall surface, at the time of application, must be dry, and not colder than 50 degrees F. The soap solution is applied at boiling temperature. This coat is allowed to dry for 24 hours, when the alum solution, at about 60 to 70 degrees F., is applied. This method of waterproofing has been in use many years and has proved quite effective. As it prevents moisture getting to the brick, it naturally prevents efflorescence also. It is recommended that aluminum sulphate be substituted for alum in the solution noted above, as being cheaper in first cost and in quantity required.