All About Glass

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Mappae Clavicula

All About Glass

The oldest of the Rakow Library’s holdings, this 12th-century Latin manuscript might best be described as a chemistry book for the medieval artist.

The Mappae clavicula presents more than 200 recipes for making various substances used in art and craft. In these formulas, ingredients found in the natural world are precisely combined to produce a variety of colors and metallic effects such as gold, silver, and copper for painting, writing, and ornamentation.

Fig. 1: First page of the Mappae clavicula. Note the words “mappe clavicula” in the first line.

Fig. 2: Detail of the words “mappe clavicula” in the first line.

Our understanding of the Mappae clavicula was considerably enhanced by the first complete English translation published in 1974 by Cyril Stanley Smith and John G. Hawthorne. Translating a medieval manuscript can be much like solving a puzzle. The title of the Mappae clavicula was a basic piece of the puzzle for Smith and Hawthorne, who settled on “A Little Key to the World of Medieval Techniques” as the most meaningful translation. In their introduction, they note that the version of the Mappae clavicula owned by the Rakow Research Library is the most complete copy known to exist.

Some of these many recipes involve glass. For example, recipe number 69 in the Smith and Hawthorne translation is for “Giving to Glass the Nature of a Stronger Metal” and uses a mixture of egg whites and mistletoe juice to accomplish this. Another recipe for staining glass purple calls for coating the glass in dragon’s blood.

The Mappae clavicula is valuable not only for its historical content but also as an artifact of medieval material culture. The manuscript was probably copied from more than one original source in the cloistered setting of the monastic scriptorium. Since copying by hand was the only way in which a book could be reproduced before the introduction of printing, each manuscript was a unique object. In various sections of the Mappae clavicula, the size of the writing and the style of the Romanesque lettering are different, indicating that two scribes may have collaborated in its production.

In the absence of illustrations, chapter headings and initials in red and green provide relief from the monotony of the sepia-colored ink and help to organize content. For the scribes, the tedium of copying was relaxed by the small measure of artistic freedom they could exercise in designing the initials. Some of these letters seem to have sprouted tails, while others imitate architectural elements such as fluted columns and delicate crowns.

Fig. 3: This page of the Mappae clavicula contains one of the more elaborate initials in the manuscript.
Fig. 4: Detail of the "S" in the Mappae clavicula.
Fig. 5: The "A" initials on this page and in Figure 8 show the creativity of the scribes.
Fig. 6: The "A" initial on this page and the three in Figure 7 are quite different.

Fig. 7: Details of the "A" initials in Figures 7 and 8.Most manuscripts from this period are religious in nature, but the Mappae clavicula is a book of technology. Uniting as it does the artistry and technology used by medieval artisans, this 12th century manuscript uniquely embodies the inventive spirit that infused the Middle Ages.

Published on October 7, 2011