Offset lithography

Cheap and effective methods of colour photographic illustration did not appear until the 20th century, after decades of experimentation. By the 1880s the half-tone block could render gradations of tone in a monochrome print.

A piece of glass marked with fine hatched lines was placed between the photographic negative and the photosensitised metal plate. The light penetrating this screen made dots of varying size on the plate’s coating, according to its intensity. When the resulting etched block was printed the dots appeared merged to the human eye in such a way as to produce tonal effects.

The 1890s saw the advent of three-colour half-tones, in which three plates were made, each from a negative with a different colour filter (red, blue and yellow) and of multicolour photogravure, though the latter was too expensive for common use.

In the early 20th century a third method of colour printing arrived, offset lithography, whereby the image on the inked lithographic plate was transferred or ‘offset’ to a rubber cylinder and thence to the printing surface. Offset lithography proved quick and cheap, producing photographic illustrations of a consistent appearance, though the quality was not as high as that obtained with photogravure. It was, and is, widely used in the printing of books, magazines, newspapers and stationery. 

By the 1950s offset lithography was in use around the world and in our original exhibition we displayed issues of the West African annual  that illustrate this technique.

The London editor of the West African annual, Charles Nida, declares in his foreword to the 1958 issue that his aims are ‘to offer an outlet to budding West African authors’ and ‘to give West African printers something of the nature of a quality publication into which to “get their teeth”’.

In his 1957 foreword he reports on a recent visit to the Gaskiya Corporation’s printing works in Zaria, where he saw Nigerian printers at work. While admitting that the resulting publication owed much to the training and supervision provided by the British and Danish managers, Nida stresses that the African printers ‘set the type and printed the pages – all of them, including the coloured cover’ and hopes that these printers will form ‘a nucleus of skilled craftsmen … fitted to cope with most kinds of modern printing work’, who ‘should prove of considerable value as teachers to a future, independent West Africa’.  

Nida encouraged contributors to send in monochrome or colour photographs depicting scenes of West African life. The quality of both originals and reproduction was not always high and some of the photographs appear blurred. This is especially noticeable in the front cover illustration of Kumasi, Ghana.

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