The magic of purple pencil
Tuesday 17 April 2007 by gajraw. 1 comment
George Lambert: Gallipoli and Palestine Landscapes, Exhibition, Conservation
Before the invention of the photocopier, people had to rely on all sorts of different techniques to make copies of correspondence and text. In the 1780s there was letterpress copying where a dampened sheet of thin tissue paper was laid against the inked side of an original document and then put in a press. The two sheets were pressed together producing a mirror image of the original text on the tissue. Due to the tissue’s semi-transparency, when it was held up to light the mirror image text could easily be read through from its back. The inks used in this process were made from oak galls (gallotannates) and logwood. The most commonly used wet ink copy paper was high-quality Japanese tissue. The disadvantage with ink press was that the tissue paper had to be thoroughly wet to get the mirror image and only a few copies could be made. This made it a costly and complicated process.
Copying pencils were invented in the 1870’s and within a decade had overtaken the wet ink press method of letterpress copying. The younger generation might not know the magic of the colourful purple pencils. They were the predecessor to the ball point pen. Similar in appearance to graphite pencils, copying pencils contained a dye which turned purple when moistened. They were marketed as a product which could not be erased because the main component of the pencil was an aniline dye which produced a purple colour when dissolved in water or alcohol. The other components of the copying pencil were clay (kaoline) and graphite. Other colours used were red, black, green and combinations of dyes. The aniline dye in the copy pencil produced stronger copies and more copies. Another advantage was that the aniline dye was not affected by exposure to the air (as was the ink) and therefore copies did not have to be produced instantly.
The copying pencil rose to prominence during the First World War as it could not be smeared or erased easily. Archival records of the time show that Great Britain bought thousands of copying pencils per week to supply to British and Allied officers. These pencils were much more convenient to use in the field than were pen and ink.
George Lambert used copying pencil in some of his drawings including the work (left) Last Brigade Headquarters in the north: leading to Brigade Headquarters, with artist's notes (loose sheet from the`Brown book' ART11393.344). He was possibly issued some pencils by the War Records Section when he was commissioned and he also could have picked them up when travelling with the troops. Sometimes Lambert's drawings were done completely with copying pencils and sometimes with a mixture of copying and graphite pencils. At the Memorial there are a few examples of these works. In preparing drawings for the George Lambert exhibition, we carefully surveyed all the drawings to make sure which ones might have copy pencil in them. Copy pencil drawings are easily identified under the microscope by their purplish tone, however identifying combination drawings can be problematic. To avoid dissolving the copy pencil component of a combination drawing, professional conservators conduct thorough solubility tests for every colour before washing and cleaning these delicate items.
Gajendra Rawat, Paper Conservator
1. Dube, Liz (1998). The Copying Pencil: Composition, History, and Conservation Implications. AIC, The Book and Paper Group Annual, Vol 17, 1998.