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Engineering and Technical Blueprints

Engineering and Technical Blueprints

The cyanotype or blueprint was invented by Sir John Herschel in 1842. His experiments were copies of small engravings (see for instance 28304, 76956, 81196). The process was recognised and used immediately as a simple and surprisingly effective method for contact copying delicately-structured, semi-translucent things such as lace (11893) and botanical specimens, the outstanding example of the latter being the corpus of cyanotypes of algae begun by Anna Atkins in 1843 (11887).

By then the primitive photogenic drawing had already been superseded for most purposes by the more sophisticated calotype, which itself gave way to the wet collodion glass negative in the 1850s. But in fact the basic printing-out, contact-copying paper processes were unrivalled for direct copying of flat originals with clean lines and contrast, such as leaves or drawings. For applications where the cyan blue colour, hardly suitable for some photographic uses (such as portraits), did not matter, and where a negative image was acceptible (or even advantageous; see narrative to 30855), Herschel's cyanotype was ideal. It was straightforward to use (compared to most photographic processes), its materials were cheap, its fixative was water, and its colour was easy on the human eye. The cyanotype image even proved stable and durable, with much less tendency to deteriorate than most photographic processes.

Yet in fact it was very little used for a generation after Anna Atkins. A simple geometrical diagram made by Henry Perigal in 1858 (11896) anticipates the kind of uses it would be put to. But who it was who pioneered using it as a professional method for copying engineering, architectural, and technical drawings and plans has not been recorded. It seems to have become established during the 1870s, and the word 'blueprint' was first noted in the 1880s. The 1891 edition of Chambers's Encyclopaedia reported that 'the Cyanotype or Blue printing process' was 'chiefly used for copying plans and drawings'. It was universally employed for such purposes, and survived in regular use well past the mid 20th century, making the word and concept of 'blueprint' familiar to all.

The straightforward blueprint was negative (white lines on blue ground), but positives (blue lines on white ground) were also used. A process similar to the latter, the diazo or 'whiteprint', replaced it, though they co-existed for decades. And electrostatic copying (xerography), or occasionally microfilming and printing from microfilms, followed, especially from the 1960s. Of course the whole business was largely swept away at the end of the 20th century by the creation and storage of technical drawings and designs on computers.

So much did the blueprint become associated with authoritative technical diagrams and designs that not only was the word applied to detailed designs of whatever colour or process, but such drawings and diagrams were even printed and illustrated in imitation of blueprints, as if to lend them authority. The Mullard 'blueprints' for home-assembled radios issued in 1930, for instance, accurately mimic the colour and appearance of blueprints, but in fact are conventionally printed using blue ink (documents accompanying 71604).

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The Museum has not deliberately collected technical blueprints, and has only a few specimens of them, usually occurring incidentally within archives of scientific or technical papers. An archive such as that of the instrument maker Elliott Brothers (later Elliott Automation) might be expected to contain large numbers of blueprints of instrument designs. Photographs of their drawing office (for instance in the album 11839) show the large portfolios or guard-books in which drawings or copies were kept for reference; but it seems that they were not preserved, presumably because of their cumbersomeness. A few blueprints occur within the archive, of course (such as those in the patents album 11980), as do, in the more modern period, the whitish coloured diazos that replaced them.

Surprisingly however the largest group of blueprints preserved in the Elliott archive consists not of engineering drawings but of ordinary photographs, printed from glass negatives by the blueprint process. Removed from one of the drawing office binders, the 280 large sheets on which they are pasted are estimated to contain about 1,680 photographs (11840). They form a reference set of the company's photographs of its products, as used in catalogues, instruction manuals, and promotional material, providing an easy means for managers and sales and publicity staff to view the stock of images. The blueprint process would be used because it was readily available at the factory, as well as cheap and visually clear. They seem to have been made in the 1920s, at which period similar prints were also used to illustrate the instruction booklets and technical reports issued with some Elliott instruments (such as 11978 and 11982).

A fine example of the conventional engineering blueprint is Sir Howard Grubb's 1897 design for a chronograph for the newly-founded state observatory at Perth, Western Australia (11906). Based in Dublin, but the world's foremost manufacturer of astronomical observatory equipment, a blueprint was the ideal thing for Grubb to send to his customer in Australia. The existence of a blueprint in Oxford, however, illustrates another advantage - when Oxford's Radcliffe Observatory wanted a chronograph later the same year, Grubb was able to send them in this form the design for the Australian chronograph, and then adapt it to their needs.

Blueprints are even found attached to instruments. Being a readily available, cheap, and robust process, it was sometimes used both by manufacturers and by owners of electrical testing instruments (for instance) to provide a circuit diagram, set of instructions, or other operational memorandum. These are often stuck inside the lid (examples include xxx, xxx). Similarly a blueprint was the perfect way for a technical person to provide himself with a cheap, accurate aide memoire, such as a circuit diagram (11903, 11971) or a reminder of formulae or calculating procedures (for example 11969, stuck in the back of a book of mathematical tables). The ultimate utilitarian use of the blueprint is the fire-hose calculator, part aide memoire, part calculating instrument, ingeniously improvised by two fire officers in 1941, during the darkest time of the Second World War, to assist less experienced auxiliary firemen (67219).

new commentary added April 2011: to be completed shortly

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