The American Printer: A Manual of Typography / Containing practical directions for managing all departments of a printing office, as well as complete instructions for apprentices; with several useful tables, numerous schemes for imposing forms in every variety, hints to authors, etc.

by Thomas MacKellar

IMPOSITION

Comprehends a knowledge of placing the pages so that they may regularly follow each other when printed and the sheet is folded up; and also the mode of dressing chases and the manner of making the proper margin. As many pages as are required for a whole or half sheet being made up, the compositor lays them upon the imposing-stone, placing the first page with the signature to the left hand facing him, and then proceeds according to one of the schemes on [pp. 150-199]. These will be found to contain every necessary imposition,—viz. folios, quartos, octavos, twelves, sixteens, eighteens, twenties, twenty-fours, thirty-twos, thirty-sixes, forties, forty-eights, sixty-fours, seventy-twos, ninety-sixes, and one hundred and twenty-eights. We also introduce schemes for imposing from the centre, by which means the blank or open pages may be thrown in the centre of the form, leaving the solid pages on the outside to act as bearers for the rollers, as well as for the better regulation of the impression.

All odd matter, for any form, should be divided into fours, eights, twelves, and sixteens, which is the groundwork of all the impositions except the eighteens, which differ from all the others; for instance, sixteens, twenty-fours, and thirty-twos are only octavos and twelves doubled, or twice doubled, and imposed in half sheets: for example, the sixteens are two octavos imposed on one side of the short cross; the twenty-fours are two twelves imposed on each side of the long cross; and a thirty-two is four octavos imposed in each quarter of the chase. Thus, a sheet may be repeatedly doubled. By this division, any form or sheet may be imposed, always bearing in mind that the first page of each class must stand to the left hand, with the foot of the page toward you. Having set down the first page, then trace the remainder according to the scheme which applies to its number; in proof of which, the standard rule for all other impositions may be adopted,—namely, the folios of two pages, if placed properly beside each other, will when added together make one more than the number of pages in the sheet; that is, in a sheet of sixteens, pages 1 and 16 coming together will add up 17, and so 9 and 8 will make 17, &c.

In half sheets, all the pages belonging to the white paper, and reiteration, are imposed in one chase. So that when a sheet of paper is printed on both sides with the same form, that sheet is cut in two in the short cross if quarto or octavo, and in the short and long cross of twelves, and folded as octavo or twelves.