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Symposium Report:
Studying Medieval Manuscript Pigments with Cheryl Porter

The medieval manuscripts held at Harvard form an important and beautiful link to our intellectual and cultural past, and preserving them is a special custodial trust. Light, heat, inappropriate humidity levels, abrasion, and inherent weaknesses are among the key factors contributing to their gradual deterioration. Identifying and understanding the materials used in manuscript fabrication informs the measures that can be taken to protect and conserve them.

To help educate the Harvard community regarding the physical properties of manuscripts, the Weissman Preservation Center invited Cheryl Porter, an independent researcher and lecturer in medieval pigment identification, fabrication, and conservation, to lead a symposium during the week of October 30, 2000. Porter trained as a paper conservator at the Camberwell School of Arts and Crafts in London. Later she worked in the Pigment Analysis Unit of University College London and served as a research fellow in the art history department there. She travels internationally as a consultant, lecturer, researcher, and pigment conservator.

Inks and pigments are a little-studied area of medieval book scholarship. Some knowledge of pigments and manuscript fabrication is available from medieval artists' manuals and direct observation of a manuscript's condition. Other knowledge is attainable by recreating inks and pigments, and practicing writing or painting with them. To impart both kinds of knowledge, Porter's program combined half-day lectures with half-day practica.

Book, paper, and object conservators, technicians, faculty members, and students from many institutions at Harvard came together to hear Porter's lectures on the materials of the medieval scribe and illuminator. A smaller number of conservators attended hands-on sessions in making inks; creating pigments from earth, organic, and mineral materials; and dyeing alum-tawed skins. Conservators created charts of the different color families so as to have accurate samples from known sources for future reference. They also learned new sampling and mounting techniques for microscopic examination and identification of materials. Porter stressed the need to develop more straightforward and non-destructive tests for pigment identification than currently exist.

The inks used in medieval manuscripts are carbon blacks, iron gall, and sepia. The pigments fall into several general categories. Earths dug from the ground produce colors such as ochres, terre vertes, umbers, and siennas. The earth must be mixed with gum arabic (a binder) before it can be used as a pigment. Natural minerals such as lapis lazuli, azurite, malachite, orpiment, white lead, red lead, lead tin yellow, verdigris, and vermilion are mined and refined to make pigments. Organic materials such as woad and indigo produce blues; weld, saffron, and buckthorn produce yellows; ripe buckthorn produces green; and brazilwood and madder root produce reds. Insects such as kermes, cochineal, and lac also produce red colors.

Dyes (vegetable or insect) can be precipitated onto chalk to produce the opaque pigments called "lakes." These colors can be mixed to form other colors or can be layered so a transparent glaze modifies the appearance of an underlying opaque color. The medieval craftsman, through apprenticeship and work in a master's shop, gained the much needed knowledge, trade secrets, and experience to know what colors would and would not work together.

For Harvard's library staff, Porter's symposium provided critical information for professionals in a field where a single mistake can ruin the appearance of a hand-painted manuscript. In addition, knowing the possible ingredients of medieval recipes helps conservators understand why deterioration, unanticipated by the maker, may have occurred.

Porter's recent research indicates that some color formulas that have been taken for granted over the centuries are actually unconfirmed suppositions passed down from one scholar to the next. Purple pigments often thought to be "royal Tyrian purple" made from the murex shellfish are not always that. Porter has found that purple pigment is often really a mix of indigo and red. Surprisingly, she has been able to identify the real Tyrian purple in Anglo Saxon manuscripts. Her research suggests that the ancient Roman recipe survived in England long after it was lost in the Mediterranean.

Medieval manuscripts are exquisite tributes to the importance of the written word. They were created with great devotion and unstinting labor, and their conservation requires the same. Porter's symposium demonstrates Harvard's—and the Weissman Preservation Center's—continuing commitment to the task.

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Last modified on Thursday, April 18, 2002.