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The Apocalypse, The Hellmouth, and Spectral Imaging

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Nothing says Halloween quite like Apocalypses and giant Hellmouths. The Preservation Research and Testing Division (PRTD) wanted to know what this Hellmouth was made of. So, we dove right in.

Digital photograph of a page from "The Apocalypse of St. John".
Apocalypsis Sancti Johannis, Lessing J. Rosenwald Collection, Library of Congress, Rare Book and Special Collections Division, Digital ID:

This blog was written jointly by Tana Villafana, Meghan Wilson, Amanda Satorius, and Stephanie Stillo. Meghan Wilson and Amanda Satorius are Preservation Science Specialists in the Preservation Researching and Testing Division. Stephanie Stillo is the Curator of the Lessing J. Rosenwald Collection and Aramont Library in the Rare Book and Special Collection Division.

No block book tells the story of Hell on Earth quite like Apocalypsis Sancti Johannis (The Apocalypse of St. John). Based on the Christian Bible’s Book of Revelations, the Apocalypse of St. John describes the bloody battle between Heavenly good and Hellish evil and depicts the punishment of the wicked in vivid detail. Block books are largely pictorial, meant to disseminate Christian ideology to the mostly illiterate public. Many feature creative imagery of gruesome scenes and terrifying creatures–the wicked being punished by many-headed dragons while getting dunked in boiling oil, for example.

There’s general beheading:

Digital photograph of a page from the Apocalypse of St. John
Apocalypsis Sancti Johannis, Lessing J. Rosenwald Collection, Library of Congress, Rare Book and Special Collections Division, Digital ID:

A seven-headed leopard monster and goat-like demons (with more beheadings, of course):

Digital photograph of a page from the Apocalypse of St. John.
Apocalypsis Sancti Johannis, Lessing J. Rosenwald Collection, Library of Congress, Rare Book and Special Collections Division, Digital ID:

And lastly, literally everything covered in hellfire with a three-headed dragon thrown in for good measure:

A digital photograph of a page from the Apocalypse of St. John.
Apocalypsis Sancti Johannis, Lessing J. Rosenwald Collection, Library of Congress, Rare Book and Special Collections Division, Digital ID:

The vivid End-of-the-World imagery doesn’t stop here; you can view the entirety of Apocalypsis Sancti Johannis through the Library’s digital catalogue. If you dare.

The Hellmouth has a specific historical context. Historian Paula Fredriksen said it best, noting “Christianity began with the announcement that time and history were about to end.” The manifestation of this belief took many visual forms in the medieval period, including paintings, sculptures, mosaics, and altar furnishings. In illustrated Bibles and Gospel books of the same period, the vision of Paul’s apocalypse unfolded in the dramatic visualizations of celestial battles between good and evil, the punishment of the wicked, and the reward of the righteous. The standard western European illustration tradition for the apocalypse begins in 13th century northern Europe, maintaining a striking degree of aesthetic similarity for several centuries. Extant 15th century block books of the Apocalypse, hand-printed in Germany and the Low Countries conform to this pictorial tradition. Though separated by two hundred years, there is an obvious similarity between the Hellmouths in 13th and 15th century illustrations. Both images visualize the jaws of hell, represented by the double-headed monster containing a lake of fire that engulfs the false prophet and those who adopted the mark of the beast. The bottom image shows the mouth delivering up the dead to hear their sins read from the book of life and stand for judgement.

Side by side comparison of European illustrations of the Hellmouth.
Left: Apocalypse. c. 1250-1260. Coloured drawings based on a model of the school of St. Albans (southern Hertfordshire, England). MS. Auct. D. 4. 17. Bodleian Library, University of Oxford. Right: Apocalypsis Sancti Johannis. [Germany, 1470]. Lessing J. Rosenwald Collection, Library of Congress.
Block books are rare and had a relatively short production span. The years between 1440 and 1470 marked the evolution of the single leaf woodcut into a more complex narrative design that resembles a contemporary codex. The most popular terms for these are block books or xylographic books, meaning illustrated books (text and images) made completely from carved and inked wooden blocks without moveable type or a printing press. Once the woodblock was ready for printing, it was thinly inked with a dauber or printers’ ball and a sheet of dampened paper was laid atop it. The paper was carefully rubbed with a dense leather ball, creating a deep – and somewhat uneven – impression. Once the impressions dried, a colorist applied both mineral and organic (dye-based) pigments either free-hand or through a stencil. Block books hit a particular height of popularity in the 1470s, after which their production greatly decreased in Western Europe.

While only a few survive, mostly as fragments, the Library’s Lessing J. Rosenwald Collection is fortunate to house several of the remaining block books in existence.

Unfortunately, block books contain no printer’s emblem so it can be difficult to determine the place or exact date of printing. This is where PRTD can step in and take images of the unseen using spectral imaging. Multispectral imaging (MSI) is a technique that captures information just outside of the visible light range. MSI can recover obscured or deteriorated content, characterize inks and pigments, and reveal details about historic creation methods.

Digital photograph of PRTD's imaging system.
PRTD’s multispectral imaging system, which illuminates in the ultraviolet, visible, and infrared spectrums, revealing information unseen by the naked eye. Photo Credit: PRTD
Image of two different watermarks found in the papers.
Images of two watermarks. Photo Credit: Meghan Wilson.

Hidden imagery in the form of watermarks corporealize when light is shined through a piece of paper. Watermarks help establish provenance of objects by providing information about the paper’s origins. Each watermark design is generally unique to specific papermakers from specific geographic regions in specific time periods. They’re like a trademark of sorts. Two watermarks were found in the Apocalypse of St. John – a bull head and a tower with a crown. A bull head was one of the most prevalent European medieval watermarks found in countless variations. It takes careful examination of the presence and positioning of horns, ears, eyes, and nostrils, as well as motifs above the head like crosses, flowers, or even sometimes serpents to distinguish them from one another. Comparisons made to online watermark databases confirmed these two specific watermark designs are congruent to others found in late 15th century German books.

But how exactly did the Hellmouth manifest within the pages of the Apocalypse? The answer can be found in the shadows and crevices that remain from the woodblock imprint. Raking light, positioned at a low angle so it skims across the surface of the page, enhances the topography of the paper and renders the indentations created from the woodblock printing process.

A racking light angled image that shows paper texture.
Raking infrared illumination causes most of the pigments and inks to seemingly vanish, providing a clearer image of the imprint in the paper.

Analysis of the Apocalypse continued by investigating what pigments made the golden halos of angels and the demonic fires of Hell come to life in the prints. Multispectral imaging was a starting point in their identification. We looked for unique characteristics that can manifest within the different spectrums of light. For example, under ultraviolet (UV) light some pigments emit a glow called fluorescence. Others absorb the light and render as dark shadows in the image. In the image below you can see the fluorescent glow of the pink pigment. This helps narrow down which pigment it can be because only certain ones have this characteristic. Additionally, you can see that the green pigment looks completely black. This led us to believe it might be a copper-containing pigment like malachite or verdigris because copper absorbs in UV.

A page from a block book illuminated with ultraviolet light and its respective color photograph.
UV illuminated page (left) and its respective color photograph (right). Photo Credit: Meghan Wilson

Another method to identify pigments via photographic techniques is false color infrared (FCIR) image processing. This sorcery involves rearranging the red, green, and blue channels of a color image and combining them with an infrared image. The result is a composite that renders colors different than what would be observed naturally by the human eye (called a “pseudocolor”). Some inks and pigments have specific responses that can uniquely identify them. For example, iron gall ink responds in a red or pink hue as compared to most other inks that remain black or a very dark teal. This is how we were able to identify that it was iron gall ink used to make these woodcuts, serving as the outline and block text of each print. Iron gall ink was not used as a printing ink historically. However, when sufficiently thickened, it was used as ink specifically for woodblock prints by means of rubbing.

Examples of black inks after false color infrared image processing.
Left: False color infrared image of lab-made samples of various historic inks. Iron gall ink, seen in the top left, renders as a unique red. Right: False color infrared image of the Apocalypse. The printed ink responds as a brownish-red, indicating iron gall ink, Photo Credit: Meghan Wilson
Photograph of analysis team working with block books.
Preservation staff conduct non-invasive FORS and FTIR analyses with curator Stephanie Stillo. Photo Credit: PRTD

The pigments were still a mystery. They haunted our thoughts, scratching at our brains until we could figure out what they were. We needed to use some additional instruments, spectroscopic techniques like x-ray fluorescence (XRF), fiber optic reflectance spectroscopy (FORS), and Fourier-transform infrared spectroscopy (FTIR). Spectroscopy simply involves different ways of shining light onto an object and measuring the light that bounces back. X-rays provide elemental information, telling us if the pigment contains iron, cobalt, zinc, or the like. Visible light provides information about the pigment’s color and how it’s seen to the human eye. Infrared light measures molecular vibrations, identifying things that are invisible to the eye like coatings and binders the pigments were mixed with. These methods are non-invasive, fast, and the different techniques complement each other rather well. For example, XRF confirmed our assumption that the green pigment contained copper and was thus either malachite or verdigris. FORS and FTIR both identified unique peaks in their spectra to distinguish that it was in fact verdigris and furthermore that egg yolks (known as “tempera”) were used to bind the pigment into a paint when it was originally made.

The palette of the Apocalypse of St. John was limited yet consistent throughout the book. Raging hellfire was colored with red lead, angel wings and greenish demon spines with verdigris. The Hellmouth and many of the angels’ robes were painted using brazilwood, an organic red.

Photograph of analysis team working with block books.
Meghan Wilson and Stephanie Stillo examining a block book during analysis. Photo Credit: PRTD

Although we’ve talked most intensely about The Apocalypse of St. John, we imaged and analyzed five of the Rosenwald’s block books, uncovering watermarks and identifying pigments congruent with materials used in the late 15th century Germany and the Netherlands. This analysis both strengthened and broadened our historical knowledge of block books. Using complementary analyses provided a holistic overview of the material composition of the Library’s block book collection, finding many similarities and even a few interesting outliers across them.

In our exploration, we braved the supernatural. We observed eerie shades, ethereal, spectral, and downright ghoulish. But we ain’t afraid of no ghosts. Happy Halloween from the Rare Books and Special Collection Division and PRTD!

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