Colouring it true

Origins of the art of colour reproduction

Art is most often viewed at one remove: as a reproduction in a book or on a poster. Usually without acknowledging it, weentrust our experience of the colours of Renaissance Venice or Impressionistic Paris to the skill, and diligenceof the printer. But a comparison of the same image in different books is often a sober reminder of the vagaries of colour reproduction.

Capturing colour on the printed page is one of the themes of “More Than Meets The Eye”, an exhibition at the Victoria and Albert Museum in London that explores the science in art and design, ending on 3 November (see Nature 407, 20; 2000). As this part of the exhibition shows and aknowledge of colour theory is of only limited help in overcoming the infidelities imposed by shortcomings in the technology and materials of printing.

Printing in many colours did not become commonplace until the nineteenth century. Some of the most glorious colour prints of this period were a technical tour de force, for each individual colour was typically applied by a separate printing plate. William Savage, appointedby the Royal Institution in London to improve printing technology, labouredfor eight years on an illustrated book, Practical Hints on Decorative Printing, finally published in 1823, in which some of the images bore the imprint of no fewer than 29 separate woodblocks.

But a technique that was in principle more economical of materials, labour had been developed 100 years earlier. By the start of the eighteenth century artists and scientists had reached a consensus that there were but three primary colours, as well as the white and black needed to lighten or darken them. Said Robert Boyle in 1664: “There are but few Simple and Primary Colours (if may so call them) from whose various compositions all the rest do as it were Result … have not yet found, that to exhibit this strange Variety[painters] need employ any more than, White and Black and Red and Blew and Yellow.”

A colour print by Le Blon, from around 1722.

To the French artist, engraver Jacob Christoph Le Blon (1667–1741), this suggested a way to create full-colour prints using just the three primary inks. If they were translucent, theirsuperposition could generate the secondary colours (orange, green purple)aswell as tertiaries and more complex shades. Black, thought Le Blon, shouldarise from superimposing red, and yellow and blue.

To capture tonal variations, Le Blon used the half-tone technique of mezzotinting. A metal plate was burred all over with a sharp implement, and thensmoothed back down by hand to a degree proportional to the lightness of the image: smoother areas retained less colour when inked. But to prepare the three 'colour separation' plates in the pre-photographic era, Le Blon had to pull off the astonishing feat of decomposing a full-colour image into the three primaries by eye.

He began to use this method in the early 1700s, butfailed to find a sponsor until he came to Britain in 1719. Here, incollaboration with the wealthy dignitary Colonel Sir John Guise, heset up a company called The Picture Office in 1720. With the permission of King George, thepartners made several thousand copies of pictures from Kensington Palace.

They were impressive, bysome accounts. Sir James Percival said of one of Le Blon's prints in 1721, “Ourmodern painters can't come near it with their colours, if they attempt a copy make us pay as many guineas as we now give shillings.” This, however was the opinion of someone unused to seeing reproductions in anything but monochrome. In reality the method had several shortcomings. Because the inks were not pure primaries, their mixtures produced somewhat dirty colours — which time has only muddied further. The three primaries did not mix to black but to murky brown, and so Le Blon was forced to add black laboriously by hand. And the plates lost their crispness after many impressions.

Le Blon's biggest handicap, howeverwasa poor business sense. The writer Horace Walpole considered him “either a dupe or a cheat, think the former”. Forced to flee England to escape his debts, hedied in poverty. His three-colour process was abandoned until photolithography, combinedwith James Clerk Maxwell's invention of colour photography, madeit practical in the 1860s.

“not science AND art”, a closing talk for the “More Than Meets The Eye” exhibition, will be given by art historian Martin Kemp at the Victoria and Albert Museum on 3 November (7 pm). Entry free