Page:On the economy of machinery and manufactures - Babbage - 1846.djvu/106

72 another part, removes all superfluous ink from the surface previously to its reaching the cloth. A piece of calico twenty-eight yards in length rolls through this press, and is printed in four or five minutes.

(88.) Printing from perforated Sheets of Metal, or Stencilling.Very thin brass is sometimes perforated in the form of letters, usually those of a name; this is placed on any substance which it is required to mark, and a brush dipped in some paint is passed over the brass. Those parts which are cut away admit the paint, and thus a copy of the name appears on the substance below. This method, which affords rather a coarse copy, is sometimes used for paper with which rooms are covered, and more especially for the borders. If a portion be required to match an old pattern, this is, perhaps the most economical way of producing it.

(89.) Coloured impressions of leaves upon paper may be made by a kind of surface printing. Such leaves are chosen as have considerable inequalities: the elevated parts of these are covered, by means of an inking ball, with a mixture of some pigment ground up in linseed oil; the leaf is then placed between two sheets of paper, and being gently pressed, the impression from the elevated parts on each side appear on the corresponding sheets of paper.

(90.) The beautiful red cotton handkerchiefs dyed at Glasgow have their pattern given to them by a process similar to stencilling, except that instead of printing from a pattern, the reverse operation,that of discharging a part of the colour from a cloth already dyed,is performed. A number of handkerchiefs are pressed with very great force between two plates