3D Collection – a Folding Sundial made of Ivory


3D digitalisation at ETH library

A project in which 20 selected objects were 3D digitalised using photogrammetry was launched by the collection of scientific instruments and teaching aids at ETH library in 2022. The images were captured using photogrammetry by Thomas Erdin from ikonaut in the summer of that year. Each object was captured about 300-500 times on a turntable in the collection’s depot. The models were then created by ikonaut and published on Sketchfab.

The aim of the project is not only to create 3D digital copies, but also to generate the associated critical questioning and testing of the 3D technology: Where and how can the 3D digital copies be used? What potential do the 3D models offer compared to the original? Who can and should use the 3D digital copies? These are just some of the questions associated with the project.

In tandem with this project, a “3D Collection” series will appear on the ETHeritage blog. Each digitalised object will be described in a blog post to be published on Wednesdays. The posts are rounded off with some comments on 3D digitalisation – for example about the selection of objects, the usefulness of the digitalised objects or technical aspects. The series kicks off today with a post about an ivory sundial.


The Tucher family – compass makers from Nuremberg

This ivory folding sundial was made by a Nuremberg compass maker named Hans Tucher. Since every sundial comprised an integrated compass, those who made sundials were known as compass makers. This compass is used for precise orientation when travelling and for the correct setting of the sundial.1

Hans Tucher came from one of Nuremberg’s best-known compass-making families. This was also the family of origin of a female compass maker Katharina Tucher. Three brothers bore the first name Hans and all three made folding sundials. Therefore, attributing the surviving artefacts to one of the brothers is often difficult. However, researchers assume that most of the objects go back to Hans II (1557-1631) or Hans III (1549-1632).2

Hans Tucher, Stadtbibliothek im Bildungscampus Nürnberg, Amb.317b.2°,f.108v.
Hans Tucher III at work, City Library
in the Nuremberg Education Campus, Amb.317b.2°, f.108v.

This portrait shows Hans Tucher III at his workplace. In front of him on the table are several ivory sundials and the tools he used to make them. A man with a turban and a sabre is visible through the window in the background. Researchers assume that the man is a Turk. The illustrator’s aim was to highlight how Nuremberg clocks were used far and wide.3 This picture is from “Hausbücher der Zwölfbrüderhausstiftungen” – an illustrated compendium of over 1,300 contemporary crafts.


From the second half of the 14th century onwards, Nuremberg, which had previously been a rather insignificant city, developed into a free imperial city of political and economic influence. In the decades to follow, it ascended to become one of the most important cities in southern Germany and turned into a centre for the production of luxury goods and for various printed products such as art prints, globes or maps. The import and export of goods also played an important role in the city.4 Starting in the late 15th century, folding sundials were among Nuremberg’s most significant export goods.5

Researchers assume that ivory was bought and processed in Nuremberg for the production of ivory sundials. During the 16th century, the material came from the west or east coast of Africa directly to Europe via the new trade routes opened by Portugal. These new trade routes led to an ivory boom in Europe.6

The first ivory products from Nuremberg included such folding sundials.7 It is not clear when the first clock was made, but its heyday was between 1580 and 1610. By the end of the 16th century, however, folding sundials were mainly prestige objects and no longer items of everyday use.8


Ivory is a material which is subject to much discussion in provenance research. And rightly so, since it often comes from former colonies. The handling of ivory as a technical cultural asset, such as scientific instruments, is complex. It is often almost impossible to determine the exact origin of the material and the time of its import or processing. Nevertheless, even in the case of technical cultural assets, questions about colonial entanglements must be asked and it is the responsibility of the collections to do so. Especially materials such as ivory or even rubber as a precursor of plastic, which are found in large quantities in scientific instruments, may be colonial materials whose extraction involved the exploitation of people and landscapes.9

But not all objects made of ivory necessarily come from a context of injustice. This term is used in provenance research when the origin and ownership of an object is associated with asymmetrical power relations.10 Fossil ivory was – and is – also used in the making of ivory objects. This comes from mammoths and is stored under the ice sheet of Siberia.11 This material is not associated with a context of injustice in the sense described above. Moreover, ivory was already used in ancient times and an ivory trade already existed before the colonial era: one which extended through the Sahara to the Mediterranean and whose trading partners were regarded as equals.12 It is not until the 19th century that we speak of the “ivory rush”, where colonial power relations play a key role.

No known figures exist for the period of origin of the folding sundials shown, but for 19th century, we do have some: the 1890s saw the German colonies in Africa alone export 208,000 kg of ivory per year. Based on contemporary calculations, the number of elephants killed per year is estimated to be around 10,000.14

We have not (as yet) been able to determine whether the ivory sundial on display originates from a context of injustice. Where the processed ivory came from, as well as how this sundial came to be in the collection, remains a mystery. No documents on the sundial have survived. Any information on this (or similar) objects can be sent to scientific-instruments@library.ethz.ch.

3D Digitalisation

Object selection
The ivory sundial comes from the collection of Rudolf Wolf (1816-1893). Wolf was a professor of astronomy, head of Semper Observatory, director of the library of the Polytechnic (today ETH) and a passionate collector. He created an inventory for his collection in 1873. Unfortunately, it does not tell us anything about the origin of the digitalised sundial. No clear indication is given as to whether Rudolf Wolf bought it or received it as a gift.
What led us to select this object for the 3D digitalisation project was the fact that the associated research debates are highly topical.
Moreover, it is one of the oldest instruments in the collection, which testifies to great craftsmanship and is of huge importance for the collection’s teaching purposes. Thus, this sundial is also on display in permanent exhibition “Exploring the Sky – A Look at the Rudolf Wolf Collection” in Semper Observatory. While the object in the display case is only visible from the front, the 3D digital model also provides a detailed view of the two backs as well as details such as handwritten additions or embossed stamps. Thus, the 3D digital copy can be advantageously shown as a supplement to the original on guided tours.

Photogrammetry and modelling
Due to the nature of the material, the images were easy to capture using photogrammetry. The ivory is matt and has no distracting reflections. The image was captured in two folding states. However, the polus thread that casts the shadow could not be captured and had to be modelled manually afterwards, which is clearly visible. The red string in the model therefore does not correspond to the original string.

1. Compare: Lloyd, Steven A.: Ivory Diptych Sundials, 1570-1750, Cambridge Mass. 1992, pg. 33.
2. Compare: Gouk, Penelope: The Ivory Sundials of Nuremberg 1500-1700, Cambridge, 1988, pg. 49-58.
4. Compare: Gouk, ins. pg. 36-48.
5. Compare: Schewe, Roland: Eine Nürnberger Klappsonnenuhr von Thomas Tucher. Die besonderen Materialwertigkeiten exotischer Werkstoffe; in: Jahresschrift/Deutsche Gesellschaft für Chronometrie 43, 2004, pg. 153 - 167, here pg. 157.
6. Compare: Lloyd, pg. 36.
7. Compare: Gouk, pg. 28.
8. Compare: Schewe, pg. 154.
9. Compare: Wörrle, Bernhard: Technisches Kulturgut mit kolonialer Provenienz am Deutschen Museum, Vortrag gehalten an der Fachtagung Provenienzforschung Technisches Kulturgut, Händler, Museen und Sammlung, 30.03.23.
10. On the subject of provenance research and collections, see: Deutscher Museumsbund e.V. (Hg.): Leitfaden, Umgang mit Sammlungsgut aus kolonialen Kontexten, Berlin 2021.
11. Compare: Deutsches Elfenbeinmuseum Erbach, WWF Deutschland (Hg.): Auf den Zahn gefühlt. Handel und Kunst mit Elfenbein, Frankfurt a. M. 2008, pg. 4.
12. On the ivory trade compare: Deutsches Elfenbeinmuseum, pg. 20-23, Gouk, pg. 32-48.

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