Tech Biz Writing

Modern technical books which are not generated in-house by newer techniques like digital printing, are usually printed by the offset-litho method. However, this system was not always the market leader, and it’s worth our while to have a quick look at some of the earlier processes, if only to gain an insight into the mystique of printing, which still accounts for many recruits into the publishing business.

Many printing methods have been invented over the eleven centuries since the Chinese produced the first printed book. All of them fall into one of three categories:

* Relief
* Intaglio
* Planographic

Relief printing as its name implies, depends on the face of each character or line protruding above the surface of a block into which it is cast or placed. Ink is applied to the face of the letter and adheres to the paper during contact. Letterpress, the oldest method of commercial printing, falls into this group. Originally, moveable type was taken from one of two cases: an upper case for capitals, and a lower case for the rest, and arranged by a compositor in a composing stick, after which the composed line–presented backwards–was transferred to a tray known as a galley.

Mechanization brought the Monotype machine, which cast single characters to order, and the Linotype machine, which cast a whole line of type from molten metal. The galleys were subsequently assembled into pages, a number which were locked up together in a frame called a chase, making up a forme, from which one side of a large sheet of paper forming a book section was printed.

The letterpress process was, and is, flexible and reliable, if laborious, and maintained its pre-eminence for five centuries until photographic developments allowed lithography to replace it. Anyone who has sweated over a letterpress book, hand-setting moveable type, and printing page by page, will thank modern computer technology and the almost effortless typesetting achieved with Word, WordPro, and their cognates.

Intaglio printing is the opposite of the relief method. Examples are gravure (line engraving) and photogravure (a photographic process using dots of varying size to form an image, and famously mentioned in the song Easter Parade). This system is still in use in its modern-day equivalent of inkjet printing.

William Blake, no less, invented an extraordinary technique for printing both text and illustration from one engraved plate. His method, though, was more relief than intaglio, because he literally painted on his words and pictures, and used an acid to cut away the rest of the copper plate to a depth of around 1/16th of an inch. By inking parts of the relief with different colours, he was able to achieve those near-miraculous effects that we so admire today. But, it should be said, his technique was so endlessly time-consuming that no technical writer should ever contemplate following his example!

In the two true ingalio variants, the characters themselves are cut, or etched, into the surface, rather than standing out above it. Low viscosity ink is applied to the surface so that the etched gullies are filled. The remaining ink is mopped up, or scraped away. When paper is applied to the printing plate, the ink in the gullies is lifted out by suction.

In the planographic process, the image is situated on the surface of the plate. The underlying principle is simplicity itself: grease repels water but retains ink. The characters are first impressed on the plate, usually by photographic means, and coated with a thin layer of grease. Water is washed over the surface, but is rejected by the greasy areas. On application of the ink, the grease on the image retains it, while the water over the rest of the plate repels it.

At the beginning of the 20th century, offset lithography was developed in Germany. This improved method involved transferring the matter to be printed from the plate by an intermediate cylinder to the paper.

Offset litho was at last a cheap, flexible method for printing large quantities of paper. And combined with the fact that the plates could be produced ever more quickly by chemical transfer, direct photography, or electrostatic processes, the scene was set for the technology’s ultimate dominance. It retains it to this day, although variations on the laser printing method: docuprinting or digital printing/copying, are set to replace it in short measure. Already it’s clear that some newspaper supplements are printed in this way, and the development of this process is probably unstoppable.

Somewhere between intaglio and planographic processes come silk-screen printing and the old wax-stencil duplicating (Roneo), where the ink is squeezed through a master from the back to the front onto a flat, or cylindrical, surface. Silk-screen printing can be used on a variety of surfaces from cloth to metal, producing a relatively high quality image. It is still used for T-shirt printing and in a range of art forms, usually of the cottage industry type.

Colour printing is effected by making a series of passes over the same paper, each in a different base colour which merge to give the finished effect. The combination of primary colours, if correctly aligned, gives a full chromatic image.

An author should have a basic understanding of these methods and the main areas in which each is involved. Again, modern digital printers are now the systems of choice in office environments and for many documentation situations. In others, the older technologies still hold sway — litho, especially. Lithography requires some attention throughout a print run to maintain quality, but is suitable mainly for long runs and has the edge over rivals in cost and speed. For short runs (up to 1000 copies of a booklet, for example) fast laser from a computer file, will probably be used.

Next: 36. Technical Illustrations.

This entry was posted on Wednesday, July 12th, 2006 at 12:14 pm and is filed under Technical Writing, Business Writing, Publishing, TechBiz Writing, Educational Textbooks, Documentation, Design, Photography. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.