Areas of black are photographed and treated throughout exactly in the same

way as line, and their edges may be as fretted as you wish. The thing to beware of with large areas of black is that, when reproduced on cheap paper, they show through on the other side and can completely ruin the effect of someone else's advertisement. To avoid this the newspapers break up large black areas with a stipple of white dots.

There is a process by which line drawings can be reversed so that a drawing done with a black line on white paper may be reproduced as white on black. This device may give unexpected life to a dull drawing, but is of not much use in purely descriptive work.

A half-tone block can be made from any drawing done in wash, or from a photograph. As with a line block, the original is photographed to the required size on to a piece of sensitised glass, and then transferred to the sensitised metal, where it appears in reverse ; but the photographing takes place through what is known as a " screen." This screen is composed of two sheets of glass pressed together. On each of these are engraved equidistant parallel lines, the sheets of glass being so placed that the lines on one cross those on the other at right angles. When you hear these screens spoken of by numbers such as 50, 65, 85 and so on, it simply means that there are 50, 65 or 85 of these rulings to the inch. The coarsest screen in general use is 45, the finest 200. The wash drawing, when seen through a screen, appears to be broken up into tiny dots, and so is it photographed.

You have only to look at a photograph or wash drawing in a daily paper to see with the naked eye that it is composed of innumerable tiny dots ; this simply means that a coarse screen was used, making comparatively large dots ; the screen for a paper like the Daily Express being 65 rulings to the inch. A publication like Vogue or The Sphere, for example, is printed on highly glazed paper and can do justice to a drawing photographed through a screen as fine as 133 or even finer, and you will have to look for the dots through a magnifying glass ; but they are there all the same.

You will notice that a piece of tone just half-way between black and white is made up of dots that are as big as the intervals between them, the result being like a miniature chess board ; while in a very dark tone the black dots have grown so big that they overlap to such an extent as to give the appearance of white dots on a black ground.

After the sensitised plate has received the image broken up into little dots, the process is much the same as with a line block, the intervals between the dots being eaten away with acid, as were the spaces between the lines, thus leaving a printing surface of raised dots.

Coarse screen work is generally printed on zinc (the furs from Harrods on pi. 16), finer screen work being printed on copper (the children's things for Daniel Neal on pi. 28).

Before putting any subtlety of tone and elaboration of detail into your work

you must find how it is to be reproduced, and on what kind of paper. Half an hour in a dentist's waiting-room will be enough to show you that the name of each journal is inevitably connected with a certain type of reproduction and quality of paper, but where you are to illustrate a catalogue you cannot always regard these things as a foregone conclusion. Of a large number of papers at the disposal of the man who is planning a catalogue, there are four or five from which he usually chooses.

The most commonly used is Art paper whose high glaze comes from the clay with which it is coated after manufacture, the polish being applied by passing the paper through heated rollers. A wash drawing reproduced through a 133 screen or finer comes out well on it.

Imitation art is cheaper and inferior in quality, 133 being the maximum fineness of the screen used for the half-tones reproduced on it. Super-calendered and machine finished are progressively inferior, the latter being unsuited to any but a coarse half-tone.

Antique paper is often used for catalogues and, though often of good quality, is unsuited, owing to its roughness, to half-tone illustrations. While line drawings reproduce well on it, a very fine line is less effective than a strong one, particularly if the paper is very rough.

Fashion Drawing Sections

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