What can a medieval Bible tell us about animal anatomy, workshop tools, and the hands that shaped its pages? A new study reveals that the answers are not written in the text but embedded in the parchment itself.
Published in the Journal of Paper Conservation, the article by Jiří Vnouček offers a comprehensive visual analysis of the parchment used in the 13th-century Hamburg Bible, a lavish three-volume Latin Bible now held by the Royal Danish Library. Vnouček, a Senior Researcher at that library, closely examines the calfskins that make up the manuscript and uncovers a hidden story of medieval craft, conservation, and material culture.
Using transmitted light, high-resolution images, and knowledge gained through experimental parchment-making, Vnouček demonstrates how each page preserves physical traces of its animal origins and the workshop techniques used to transform skin into writing material.
A Medieval Bible Made of Calfskin
Commissioned by Bertoldus, Dean of Hamburg Cathedral, and copied by the scribe Karolus in 1255, the Hamburg Bible is already well known for its intricate illustrations. One famous image depicts a parchment-maker presenting a stretched skin to St. Jerome. As Vnouček’s study shows, the actual parchment beneath that miniature is equally revealing.
Each bifolium—two pages joined as a single sheet—was made from a single calfskin, and the manuscript contains a total of 346 skins. These skins retain visible anatomical features including the neck, spine, shoulder blades, and tail. Some folios preserve subtle impressions from vertebrae or the pelvis, visible under raking or transmitted light.
One folio (vol. 1, fol. 135) offers a striking example. “A round, white, more transparent spot on the spine (close to the blue initial) is an offprint of the second vertebrae of the thorax,” Vnouček notes. This physical detail, invisible to most readers, reveals the specific part of the animal used and reflects how the parchment was stretched and scraped.
A Flawed Folio Becomes Art
On folio 183r of the second volume, a famous miniature shows a parchment-maker handing a freshly stretched sheet to St. Jerome. Long celebrated as a rare visual record of parchment production, the image now takes on new meaning.
“The small black dot in the centre of the skin spread out in the hands of St. Jerome may depict a slash, a defect in the parchment’s surface which the parchment-maker had repaired,” Vnouček writes. “The artist might have taken his inspiration from the stitched tear on the actual folio on which he was making the illustration.”
In other words, the illustration may depict the very page on which it was painted, complete with a real repaired imperfection.
Cut, Stitched, and Scarred
Vnouček also catalogues numerous cuts, scars, and repairs made during parchment production. Many were created during flaying, particularly in difficult areas like the neck or rump. These flay cuts often appear in parallel lines, known as “corduroy,” and can result in eye-shaped holes when the parchment is stretched.
Some of these defects were stitched shut using thread, and the study identifies multiple styles of repair. On folio 169r, a complex two-step stitch was used to align and then secure a long slash in the parchment.
🧵 1/5: I’m THRILLED to see Jiří Vnouček’s paper on the Hamburg Bible’s parchment finally published with such stunning illustrations (73 in all)!
This research shows how a careful reading of parchment tells a rich story of its creation.
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— Matthew Collins (@matthewcollins.bsky.social) March 7, 2025 at 12:49 PM
“It seems that each parchment-maker had his own style of making repair stitches, so that by comparing these sewing repairs, it is possible to recognize different parchment-makers,” Vnouček explains.
Sometimes, the repairs failed. Under the tension of drying, the thread loosened and the slash reopened slightly, preserving a visible record of an imperfect but earnest repair.
The Edge of the Animal
Several folios in the Hamburg Bible preserve what Vnouček calls “natural edges,” areas near the margins that retain the original shape of the animal skin. These can still include remnants of hair, particularly in corners or near sewn repairs. In one example (vol. 3, fol. 71), light brown hairs remain embedded in the parchment.
Veins are also sometimes visible, especially in areas where the animal was not properly bled during slaughter. Iron in the blood can react with lime, leaving reddish stains. On folio 221 of the second volume, Vnouček identifies signs of parasite activity near the shoulder, along with blood-speckled patches and holes.
“Parchment is a translucent material which is to be used on both sides; therefore, any small imperfection on the surface, flesh side, or even inside the skin… will be visible,” he writes.
Parchment-Makers’ Signatures?
Perhaps the most curious discovery is the presence of pricked letters or symbols near the parchment edge on a few folios in the third volume. These marks appear on folios 190, 192, 198, and 214 and may represent a personal signature or trademark by the parchment-maker. “Such marks… were placed on the edges of the skins and were usually cut away after the parchment had been formed into quires,” Vnouček explains.
These pricked marks would have been made while the skin was stretched on the frame, just before it dried. Their survival suggests a moment of pride or ownership in what was otherwise an anonymous form of craft.
A New Way to Read Manuscripts
Vnouček’s research belongs to the emerging field of biocodicology, which brings together manuscript studies and biological science. While traditional codicology has focused on handwriting and binding, biocodicology pays attention to the animal remains in parchment, identifying species, diet, flaying methods, and even trade routes.
“Visual analyses of parchment form an important part of the new, rapidly developing research discipline of biocodicology,” he writes.
2/5: What excites me most is how each parchment sheet reveals a complete narrative – from living animal to finished writing surface. The 346 calfskins used across three volumes preserve evidence of medieval animal husbandry, craft techniques, and workshop practices.
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— Matthew Collins (@matthewcollins.bsky.social) March 7, 2025 at 12:49 PM
Supported by the EU-funded Beasts to Craft project, Vnouček’s work draws not only on archival analysis but on his own experience making parchment by hand. The result is a study that transforms how we view manuscripts—less as passive containers of text and more as complex artefacts of medieval life, labour, and material transformation.
Jiří Vnouček’s article, “The Story of the Production of Parchment as Recorded in the Animal Skins of the Hamburg Bible,” is published in the Journal of Paper Conservation. Click here to read it.
3/5: The brilliance is in the details: neck rings show the calf’s age, tension lines reveal stretching techniques, repair stitches identify different craftsmen’s work, and even parasites tell us about animal health. Nothing is merely a “flaw” – everything is evidence!
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— Matthew Collins (@matthewcollins.bsky.social) March 7, 2025 at 12:49 PM
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