This section is from the book "Scientific Sewing And Garment Cutting", by Antoinette Van Hoesen Wakeman. Also available from Amazon: Scientific Sewing And Garment Cutting: For Use In Schools And In The Home.
Felt is a kind of cloth which is not formed of woven threads, but is beaten and pressed together. It is used mostly for hats, and is made of wool and the hair of the rabbit, hare, muskrat, and beaver.
Only very fine hair and wool are used for felting, and they must be free from grease, and perfectly clean. After the material to be used is prepared, it is put into a blower with a fan inside which revolves two thousand times a minute. In this way the very fine hair is separated from that which is coarser.
The fine hair or wool for felt hats is weighed, and then fed to a machine which forms it in this way: first two rollers, one with wire teeth and the other with rows of bristles which revolve four thousand times a minute, catch it and send it flying around. As it comes from the feeder it drifts to a copper cone where it clings because the cone is full of holes, and it is over a pit where a fan works so that it draws the air from the outside and the fibers with it. Not a single fiber escapes, and when they are all gathered around, it is sprayed with boiling water which holds it together, so that it can be felted. The felting is a shrinking, pressing process, and when the fabric thus formed is finished and dried it is firm and strong.
When a stiff felt hat is to be made, it is treated to a bath of shellac. Then it is softened and drawn over a wooden block. It is then dipped in the dyeing material. After this it is carefully shaped, and the band and binding are added.
Felt cloth is manufactured in much the same way as felt for hats, only it is made of wool, and is not formed on a cone, but is pressed in flat lengths.