will stay on the slope. But it will run down a slope and it will spatter on windy days. Rosin can be kept in place by "burning" it on with a small soldering copper just hot enough to melt the rosin. Powdered rosin in gasoline is recommended.

   The proper preparation of acid for use as a flux is of the greatest importance. It is not a job to be entrusted to a novice. The acid used is hydrochloric (or muriatic). Pieces of zinc are put in the quantity to be used until it stops working; then it is properly killed. If the killing is done hastily or by anyone not familiar with the procedure, the acid is used in a still active state and attacks the copper. Pitting ensues and the work is spoiled. The acid to be used for an entire job should be prepared several days before the work starts and allowed to stand.

SOLDER AND SOLDERING

   The only solder which should be used is the best "half-and-half obtainable. It must be composed of new tin and new lead.

   The weakness of any composite structure, be it steel bridge or copper roof, is in the joints. These must be made tight and strong. The best way to make them strong is to use wide, well-sweated seams. Excellent results have been obtained with seams two inches wide; that is, with the solder flowed over that much. A good full inch is none too wide. Lots of solder, well-flowed over, is the secret of strong seams.

   Soldering should be done slowly with thoroughly heated coppers, so as to heat the whole seam uniformly and to insure the complete amalgamation of the tin and the solder.

SOLDERING-COPPERS

   Proper soldering-coppers are most important in making tight seams. As sheet copper absorbs heat rapidly tight coppers are of no use. They do not hold the heat nor soak the solder into the seam.

   Soldering-coppers should be of heavy, blunt-end type, for these hold the heat and spread the solder. They should he moved slowly over the seam so as to thoroughly heat the copper sheets and amalgamate the tin and the solder soaked into the seam.

   The same flux should be used in soldering as is used in tinning the edges. Coppers should be properly tinned before use, and, of course, care must be used in heating to avoid burning either the tinning or the copper. Coppers must be hot through and through but not overheated.

   For upright seams pointed soldering-coppers should not be used because there is not sufficient heat in the point to heat the sheet and spread the solder. For these a flat chisel-point pattern, weighing not less than 6 pounds to the pair, should

be used. For flat seams use a blunt square-end type of copper weighing not less than 10 pounds the pair.

WHITE LEAD

   White lead in oil is a good substance for filling lock seams in copper work. It is simple to apply, is watertight, and remains so a long time. White lead has been used on copper roofs, laid many years ago, both in this country and abroad. Notable among roofs of this type is that on the State House in Boston, Mass. This roof was laid in 1887-90 with leaded seams, and is apparently as tight today as it was thirty-five years ago.

   The method of applying consists of smearing the edges of the sheets plentifully with white lead in oil and folding and locking them to form lock seams in the usual way. The viscous lead and oil completely fills the lock making a water stop.

   White lead used in this way has much to recommend it. It is cheaper than soldering, and it is durable. On flat roofs where water backs up it is perhaps better to use solder, but on free-draining surfaces white lead can be used with every assurance of satisfaction.

EDGE ON EXPOSED FLASHINGS

   It will be noted on the drawings that all exposed and unfastened flashings have the edge of the strip turned over ½ inch. This is done to give the strip stiffness against wind. Thus the sheet is held in place and the packing in of snow under the flashing is prevented. It is a practice that should be axiomatic with flashing.

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