As part of the preparations for the Colour exhibition opening in March ‘18 at the John Rylands Library, Collection Care had a visit on 25th October from Dr Maurizio Aceto, professor of analytical chemistry at The Università degli Studi del Piemonte Orientale, Italy, and Cheryl Porter, Medieval pigment expert.
Maurizio analysed purple media used in several manuscripts and early printed books using fibre optic reflectance spectroscopy (FORS) to identify the colorants.
FORS is a non-destructive test that has been used for over two decades for the identification of pigments.
Light, via fibre optics, is directed to the object and the reflected/non-absorbed light is collected and analysed by a spectrometer. The resulting information is graphed and compared to a library of data to find a match from known pigments.
The manuscripts analysed included Latin 87 (see photograph above), a 10th-century gospel book illustrated with paintings of the evangelists surrounded by purple. Purple manuscripts were produced in Europe throughout the Middle Ages for Kings and Bishops.
The purple colorant was identified as Orchil, a dye made from lichen, instead of the Tyrian purple it was assumed to be.
It has been a very interesting experience and useful to corroborate our findings regarding pigments from other analytical methods e.g. multi spectral imaging and polarising microscope.
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