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Case Closed? The Utilisation Of CT Technology In The Museum

Matthias Göggerle sat down with MuseumNext to explain how Computed Tomography (CT) technology has enabled the Deutsches Museum in Munich to digitise multi-material historical artefacts in an insightful way.

Back in 2020, the Deutsches Museum in Munich embarked on a new project to digitise its cryptologic collection using computed tomographic scans in what became known as the 3D-Cipher project. Having successfully scanned a number of other exhibits, including a WWII aircraft and automobile, the team at the museum decided to move on to its array of code-breaking and crypto machines.

To date, 60 historical cipher devices dating back as far as the 1890s have been scanned and digitally processed. From the outside, these devices are often closed black boxes that cannot be opened without destroying them. And so, CT technology allows the museum to showcase the inside of the machines and reveal the mechanisms at play from all angles.

Structural analysis, comparisons with other objects and measurements can then be performed on the CT datasets to inform research projects and give museum audiences greater insight.

“Although Computed tomography (CT) technology is a well-established tool in natural history museums, it is rarely used to digitise complex multi-material historical artefacts,” says Project Coordinator, Matthias Göggerle. “Having had a couple of previous experiences with this technology, we wrote a research proposal to digitise our cipher collection.”

Matthias continues, “The industrial CT scanner we use is different from those used in healthcare most noticeably because it operates with higher radiation dosages, in order to penetrate more dense materials.”

The benefits and drawbacks of scanning with CT technology

Not only are some of the machines at the Deutsches Museum more than 120 years old but they are also delicate and difficult to care for from a conservation perspective, due to the fact that the inner mechanisms cannot be seen with the naked eye.

One of the great benefits to researchers and conservation teams is that CT scanning makes it possible to see through the casing of the cipher machines and get a clearer picture of the health of the components inside. Matthias adds,

“From an education perspective, too, being able to show more than just the exterior of the machines to museum audiences makes the collection a much more compelling proposition.”

However, Matthias notes that this type of scanning isn’t feasible for every project, due to the significant costs and data storage required by the museum: “We worked in partnership with Fraunhofer IIS on the scanning of our artefacts. Buying our own CT scanner would be far too expensive for the museum and the financial commitment is obviously significantly more than with normal photography or other scanning techniques.

“Another key consideration is the file sizes of the CT scans. You need lots of RAM to show the many gigabytes of data it takes to capture the detail. In fact, there is also a challenge in how to pair the file format with other assets and digitised data – that’s something we are working on currently.”

Set to launch in Autumn 2023, the 3D-Cipher project will initially place the dataset for the CT scans online as a resource for researchers and to showcase the images using a combination of video, animation and an interactive CT web viewer that can be rotated, manipulated and zoomed in on.

In the future Matthias suggests that the museum intends to incorporate the scans into an on-site exhibition at the museum, as the visuals would be of great interest to visitors at a media station next to the physical artefacts:

“Some of our other artefacts are already being exhibited with supporting images taken using the CT scanner, so we expect that the 3D-Cipher project will also make its way into the museum’s gallery in the future.”

Getting up close and personal with Cipher machines of historical importance

Among the Deutsches Museum’s collection are four Enigma machines, which from the outside appear to be very similar. However, one of the functions of a CT scan is to provide a clear picture of the internal details that make each machine unique and different.

Similarly, scans of the Enigma’s successor – the Schlüsselgerät 41 – which was found highly corroded in 2017, help to demonstrate the state of the inner components of the machine in a way that simply wouldn’t be feasible without breaking the cipher open and causing irreparable damage. Matthias says,

“In the case of the Schlüsselgerät 41 it was impossible to know exactly how much damage had taken place over the years and how intact the mechanics were. Having scanned the machine we were pleasantly surprised to find that it was in better health than we expected – in fact, it seemed like it could almost work again.”

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