Copper Roofings - A Manual - 1925 - Page 23
White lead in oil is a good substance for filling lock seams in copper work. It is simple to apply, is water-tight, 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 better to use solder, but on free-draining surfaces white lead can be used with every assurance of satisfaction.
The proper lead to use is that composed of basic lead carbonate and boiled linseed oil in paste form. It must be smooth and of putty-like consistency. Lumps will make uneven seams and prevent the locks from being completely filled.
After the seams have been locked and malleted all excess lead should be carefully removed from the sheets.
As soon as a portion of the roof is finished it should be carefully cleaned of all flux, scraps and dirt. Prominent signs should be displayed, where necessary, to prevent walking on the copper, and every reasonable precaution should be exercised to keep the roof free from all foreign substances, such as mortar, scraps of lumber, paper, etc.
As the development of the characteristic green patina of copper is very much retarded by dirt, flux, etc., too much emphasis cannot be placed on thorough cleaning. Accumulation of dirt means uneven, splotchy coloring.
SLOPES OF ROOFS
The slope of roofs to be covered with flat seam copper roofing should not be less than ½ inch nor more than 3 inches to the foot.
The slope of ribbed and standing seam roofs should not be less than 3 inches, and preferably 6 inches, to the foot.
Copper will develop a beautiful patina in a few months due to natural phenomena. When it is desired to obtain this finish immediately, it can be done by the use of the following methods:
1. Clean the copper by washing it thoroughly with a strong solution of soda and hot water to remove the grease acquired in the process of rolling.
2. Apply the following solutions:
(a) 1 pound of powdered sal ammoniac to 5 gallons of water; dissolve thoroughly and let stand 24 hours. Apply to copper with a brush, covering every part. Let stand one day and then sprinkle surface with clean water.
(b) Use a solution of ½ pound of salt to 2 gals, of water. Apply in same manner.
3. A dark copper finish can be obtained by the following method: Rub off' the copper with cotton waste soaked in boiled linseed oil. Touch up soldered seams with copper bronze.
- 23 -