The analysis of the Book of Mulling has now been completed using the two techniques we have available in the Conservation Department, Raman spectroscopy and XRF. As posted before (see previous posts here and here) these are complementary techniques that together can help with the identification of pigments.
The Book of Mulling is the most complex of the four manuscripts in our project in terms of the variety of pigments and the painted effect present in the manuscript.
Up to nine different colours are apparent, and there is a greater use of translucent glossy pigments than in the other three manuscripts. The glossy quality of these pigments indicates a high medium content, with finely divided pigment particles and/or organic dyes used as colourants. This gives both a brightness to the colour and a slight effect of depth, as light is reflected from the shiny surface and the parchment underneath the pigment. The opaque pigments which by contrast are almost granular, are relatively thickly applied on top of the parchment and create a slightly embossed effect as raking light catches the surface.
This manuscript harks to the Book of Kells where a more extensive palette was enhanced by using a combination of opaque and translucence passages as well as layers of pigments, including transparent glazes.
All areas of blue that were analysed confirmed the presence of indigo. This was most notable in the hair of the portrait of Matthew (fol 12v), where the blue has been lightened with chalk white. The glossy green used for the robe, created from a mixture of blue and yellow, includes indigo and orpiment. The egg-yolk yellow halo was painted with orpiment and skin tones were created with chalk white.
The eyes of all three evangelists are blue and in each case painted with indigo; each however has a unique hair colour with Matthew distinguished by his blue-rinse (indigo), Mark (fol 35v) his brilliant red-head (red earth) and John (fol 81v) by stunning blonde locks (possibly yellow earth).
Despite knowing more about our evangelists than we did before, we have not been able to identify all the pigment used to create their images. A glossy orange used for robes and border interlace remains elusive, as does a glossy yellow. Purple, which features in various hues from pale pink/purple of initial and border decorations to a deeper purple in the robes of Matthew also remains unconfirmed. We expect all of these to be organic dyes, the purple likely to be orcein – the dye used on the Book of Kells. We hope that future developments in non-destructive instrumentation will allow us to discover more about the raw materials used to create this superb early example of book-art.
Susie Bioletti, Keeper of Preservation and Conservation and Allyson Smith, Project Scientist, Preservation & Conservation Department, The Library of Trinity College Dublin.