Digitizing Ancient Seals

How scholars document the calling cards of the biblical world

Ancient seals come in a variety of materials and colors, posing challenges to photographic documentation. Photograph by Klaus Wagensonner.

Seals are some of the most compelling and ubiquitous objects we have from the ancient Near East. Small enough to grasp in the palm of your hand or to wear as an item of jewelry, seals are either cylinder or stamp shaped. Seals were used to transmit engraved figures, symbols, and patterns onto softer materials like clay by pressing or rolling. They predate the earliest cities and lasted until late antiquity. Both seals and their ancient impressions survive in large quantities and are kept in museums around the world.

The Yale Babylonian Collection (YBC) holds more than 4,000 cylinder and stamp seals, together with more than 10,000 clay documents with seal impressions. To document such a vast collection properly and make it available to others is a daunting task. The YBC Seal Digitization Project has tackled this challenge by employing the latest photographic methods. Before we discuss these methods in detail, however, we first need to appreciate the complexity and richness of the artifacts themselves.

Seals functioned as a kind of signature in the ancient world. By pressing the engraved surface of a seal into wet clay, an individual could authorize or secure a variety of documents. Seals could also act as items of jewelry, protective amulets, family heirlooms, and statements of social position.a They were made from stone, but also shell, bone, faience, and metal. A variety of tools and techniques were used to produce a finished engraved object. Although almost all seals were pierced and could be worn (on a string or as a ring), trends in seal shape, material, and imagery changed over time.

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Scenes carved into seals pay witness to a number of activities, including banquets, offerings, contests, hunting, and agricultural practices. Depictions of gods, mythical creatures, humans, animals, plants, as well as geometric patterns and inscriptions populate these scenes. On stamp seals, the engraved imagery is usually limited to a single side. On cylinder seals, however, carvers made ingenious use of the curved surface, creating images that could repeat infinitely when rolled out. These “tiny treasures” were passed down through the generations or reworked to meet the needs or desires of the seal’s owner.

Seals offer a largely untapped resource for the study of administrative practices, social identity, religious thought, artistic traditions, long-distance trade, and more. Yet the complexity, variability, and miniature size of these objects make them difficult to document and study. Although approaches to documentation have progressed significantly in recent years, specific protocols for the digitization of seals have yet to be established. In their efforts to make materials freely accessible online, staff at the YBC have documented cylinder and stamp seals using various photographic techniques.

Agate cylinder seal from the second millennium BCE documented through a modern impression (top), photos of its top, sides, and bottom from different angles (middle), and a “digital unwrapping” showing two rotations (bottom). Photograph by Erik Eskind.

Photographs of modern impressions made in polymer clay have long been used to document and publish seals. When these are paired with a photograph of the seal itself, viewers are able to get a sense of the object as well as its engraved imagery. Our project aims to offer a fuller representation of the objects. Photographs of stamp seals highlight the array of forms from different periods and regions. For cylinder seals, profile shots capture the shape of the cylinder and depth of carving, while images of the tops and bottoms of the cylinders help identify incomplete or reworked seals.

But the relationship between the patterns of the stone and the engraved imagery can best be seen by creating what is known as a “digital unwrapping”—a kind of panorama-in-reverse that provides a 360-degree view of the surface of the cylinder. These digital unwrappings were introduced to BAR readers by Wayne Pitard, who documented seals using a Better Light digital scanning back with panoramic adaptor as part of the West Semitic Research Project.b The YBC is working with Better Light photographer Erik Eskind to develop this system, using a cyclorama light and adding an option for focus stacking to increase the resolution of deeply carved or concave-shaped cylinders. In addition, the Cuneiform Digital Library Initiative also captures the surface of cylinder seals, using a portable seal-scanning device developed through an international research collaboration. It is also possible to create a digital unwrapping by taking multiple photographs of a seal, ideally on a turntable, and then digitally stitching those images together. YBC staff are testing these approaches to determine cost, time expenditure, personnel requirements, and quality. One of the most salient discoveries has been the need to create different lighting profiles for different kinds of seals—a lustrous black hematite stone, for example, has different lighting requirements than a translucent blueish chalcedony stone.

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Capturing images of seals in a controlled environment is no easy task. YBC staff sort and clean seals prior to photography, take many photographs of each seal, create modern impressions of the seals, and then photograph these impressions—all before assembling a final composite image. All of the collection’s seals are being photographed and uploaded to the Peabody Museum of Natural History’s online portal. Although photographs, no matter how detailed, offer incomplete access to ancient objects in the sense that images cannot replicate the experience of handling a seal or pressing it into clay, the digitization of seals offers audiences worldwide an entry point for the study of the ancient world.

Elizabeth Knott is a visiting fellow at Yale University. She is working to create a website that explores strategies for cylinder seal documentation.


a. See William W. Hallo, “’As the Seal Upon Thy Heart’,” Bible Review, Spring 1985.

b. See Wayne T. Pitard, “Circular Signatures: Getting a Better View of Mesopotamia’s Smallest Art Form,” BAR, May/June 2014.


Related reading in Bible History Daily:


Practical Uses for Photogrammetry on Archaeological Excavations

GIS in Archaeology

Try the Latest Technology for Yourself

Mesopotamian "Receipts" Illuminated by 3D Technology

A New Light for the World’s Oldest Unknown Script

All-Access members, read more in the BAS Library:

Circular Signatures: Getting a better view of Mesopotamia’s smallest art form
Hi-Tech Archaeology: Ground-Penetrating Radar—New Technology Won’t Make the Pick and Trowel Obsolete
Technology and Antiquity
Cyber-Archaeology: Insights from the Holy Land

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