Photocomposition

This includes the technological units employed to transfer ink from a matrix to a support and it consists of two main stages: typesetting and printing.
Typesetting involves the joining of types and their paging up. It can be carried out manually, mechanically or by filmsetting.
In manual typesetting the single types obtained in the foundries are manually placed on the composing stick to form lines.
Mechanical typesetting (Linotype, Monotype) makes use of a machine in which the alloy is moulded in a matrix automatically created by the machine itself when the operator inserts the types on a keyboard.
Filmsetting is nowadays the most widely employed technique and it can be carried out by means of two different systems: the optical-mechanical and the electonic systems. In the first system the text is turned into a punched tape containing all the information on the type. The tape is then used by a machine that selects and exposes the matrices, then shines a xenon point source upon them and finally exposes them onto a photosensitive material. In the second system the types are stored in a computer's memory which forwards them to the filmsetting unit that then exposes the photosensitive support.
The next step involves the preparation of the printing matrices (relief or non-relief matrices) which is carried out with different methods depending on the employed typesetting type. If the typesetting had been carried out manually or mechanically an imprint is obtained, either on asbestos cardboard or on plastic material. A relief matrix is then obtained by means of casting lead (lead stereotypy) or melted gum (gum stereotypy) on the imprint. On the other hand if typesetting had been carried out by filmsetting, the photographic reproduction is transferred by UV photogravure on a zinc and aluminium plate previously treated with nitric acid. Thus a non relief matrix is obtained (printing plate).

Printing is carried out by using either the relief matrices or the printing plates previously inked. In the latter case, the ink covers only those parts of the plate that have been made lipophil by the UV treatment. The ink is then transferred on paper by the direct pressure of the matrix on the paper (typography) or by interposition of a caoutchouc roller.

Once filmsetting has been introduced, the occupational risk arising in the typesetting stage from lead dusts and vapours has disappeared. However the introduction of typesetting procedures based on the employment of computers entails the acquirement of fixed prolonged postures and may entail visual problems.
During the preparation of matrices by photogravure there is a risk of exposure to strong acids and bases and from UV rays.
The printing stage entails risk from exposure to vapours of solvents contained in the ink, risk from noise excess produced by the machinery and risk of injuries, always present wherever there are mechanisms in motion.

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Typography

Photocomposition