Page:The Art of Bookbinding, Zaehnsdorf, 1890.djvu/42

12 were at the edge of the rollers the man turned the handle, drawing the whole hand between the heavy cylinders. The accident cost him many months in the hospital, and he never regained complete use of his right hand.

Great care must be used not to pass too many sheets through the machine at one time; the same applies to the regulating screw. The amount of damage that can be done to the paper by too heavy a pressure is astonishing, as the paper becomes quite brittle, and may perhaps even be cut as with a knife.

Another caution respecting new work. Recently printed books, if submitted to heavy pressure, either by the beating hammer or machine, are very likely to "set off," that is, the ink from one side of the page will be imprinted to its opposite neighbour; indeed, under very heavy pressure, some ink, perhaps many years old, will "set off;" this is due in a great measure to the ink not being properly prepared.

Machines.—Of the many rolling machines in the market the principle is in all the same. A powerful frame, carrying two heavy rollers or cylinders, which are set in motion, revolving in the same direction, by means of steam or by hand. In many, extra power is supplied by the use of extra cog-wheels; the power is, however, gained at an expense of speed. The pressure is regulated by screws at the top.