Felt, generally saturated with bitumen and other substances, is sold in various forms useful to the engineer and builder. The following information regarding the different descriptions is from the circular of Messrs. Engert and Rolfe : -

Asphalted Roofing Felt is nearly black in colour, has a strong odour of asphalte, and is about 1/8 inch thick.

It is made 32 inches wide, and in any lengths up to 35 yards; and is used as a roof covering for temporary buildings, the lining under slates, etc., on roofs, etc.

A coat of lime whiting or whiting and size is recommended where the smell of the asphalte would be objectionable.

Sarking Felt is like the above, but only about 1/12 inch thick. It is made in rolls 32 inches wide and 30 yards long, and is used as a roof covering for temporary sheds, and under slates.

Inodorous Bitumen Pelt is of a brown colour, about 1/8 inch thick. It is made 32 inches wide, and in lengths up to 35 yards. It is used for damp walls, for lining iron houses, under slates or roofs, for laying under floors to deaden sound; for bedding girders, columns, and heavy iron work.

Fibrous Asphalte is a sort of felt well impregnated with asphalte mixed with grit.

It is made in slabs 32 inches long, and either 41/2, 9, 131/2, 18, 23, 27, 30, or 36 inches wide.

These slabs are very tough and waterproof. They are used for damp-proof courses (see Part II.), being bedded in cement or mortar; the joints overlap 2 inches, and are kept clear of mortar.

Hair Felt, for preventing the escape of heat from boilers, pipes, etc., is dry, and not impregnated with asphalte, etc.

It is made 3 feet wide, and in lengths up to 20 yards; also in sheets 34 inches by 20 inches.

The felt is classed by numbers, according to weight per sheet, as follows : -

Nos...

0

1

2

3

4

5

Weight of sheet..

Thin

16

24

32

40

48 ounces.

Thickness of sheet ....

...

1/4

3/8

1/2

5/8

3/4 inch.

This felt is attached to the boiler by a cement composed as described below, then covered with canvas and painted.

Cement For Attaching Hair Felt To Boilers

1 lb. red lead, 3 -lbs. white lead, and 8 lbs. whiting, are thoroughly mixed with boiled linseed oil to the consistency of treacle, and spread over the edges of the felt and on the side next to the boiler.

1 Patentees' Circular.

Tarring Felt

Three parts coal tar are boiled with one part slaked lime, powdered chalk, or whiting. The mixture is applied warm, and dusted with as much sand or grit as it will absorb. Stockholm, Archangel, or thick purified coal tar may be used after merely warming, not boiling.

Painting Felt For Exterior Work

First prepare with a coat of lime whiting, then paint with red lead, boiled oil, and driers (no turps), on which sprinkle fine white silver sand; over this any paint may be used.