Uses

Lead is much used by the builder for cisterns, pipes, flat roofs, etc., and from it is prepared white lead, the basis of most ordinary paint. The engineer requires it as a bedding for the ends of girders, and for other minor purposes.

Ores

Lead is not found in the metallic state, but is reduced chiefly from the ore called galena (the sulphide) by roasting or smelting in a reverberatory furnace, furnished with long flues to catch the particles of lead, which would otherwise be carried away in the smoke.

Properties

Lead is extremely soft and plastic, very malleable, fusible, heavy, and very wanting in tenacity and elasticity.

Market Forms

Lead may be purchased in cast pigs, sheets, or pipes.

Sheets are either "cast," or "milled," and are described according to their weight per foot superficial.

Cast lead, is made in sheets from 16 to 18 feet long, and 6 feet wide; it is thicker and heavier than milled lead, and has a harder surface.

' It is, however, liable to flaws and sand holes, and is irregular in thickness, on account of which it should not be used of a lighter substance than 6 lbs. per square foot.

Cast lead is often made by the plumber himself out of the old lead waste pieces and clippings that accumulate in the course of his work.

Milled lead is rolled out thinner than the other, is more uniform in thickness, bends easily, and makes neater work, but cracks if much exposed to the sun. The sheets are from 25 to 35 feet long, and from 6 feet to 71/2 wide, Sheet lead is always described according to its weight in lbs. per foot superficial.

The following Table shows the thickness of sheet lead for different weights per square foot.

Table Giving Weight And Thickness Of Sheet Lead

Weight in lbs.

per superficial foot.

Thickness in inches.

Nearest simple fraction.

1

0.017

1

2

0.034

1/32

3

0.051

1/20

4

0.068

1/16

5

0.085

5/64

6

0.101

3/32

Weight in lbs.

per superficial foot.

Thickness in inches.

Nearest simple fraction.

7

0.118

7/64

8

0.135

1/8

9

0..52

9/64

10

0.169

5/32

11

0186

11/64

12

0.203

3/16

15

0.255

1/4

The weights of sheet lead generally used are as follows (see p. 150, Part I.): - For aprons, 5 lb. lead; for roofs, flats, and gutters, 7 or 8 lbs.; for hips and ridges, 6 or 7 lbs.; thicker if much exposed.

Laminated Lead is a very thin, description of sheet used, made for covering damp walls.