Tag Archives: X-ray Microtomography

Apocalypto on TV

When the BBC heard about our efforts to Reveal the Unreadable they got in contact. They wanted to know if we had anything they could film and use for television. At the time we were working on the Bressingham Roll (see past posts) and were about to reveal the hidden text inside the roll.

A film crew came along for the day and the video below is the result.

Flying through the Bressingham Roll

To get some idea of the internal structure of the Bressingham Roll, it was instructive to generate a fly-though animation. This peels away the scroll, layer by layer showing what is underneath various layers of parchment and how they are stuck together (if they are).

The videos below show two different “cuts” though the roll. The first is parallel to the long axis of the roll. The second is across the long axis of the roll – equivalent to making slices of a Swiss roll.

In this video, you can make out some writing – in places the ink was clear enough to give a good X-Ray contrast with minimal post-processing needed to make it visible.

You can see some dark marks on the parchment in this video, some of these are ink, others are some other material in the roll that is also showing up strongly in X-Rays. It’s much harder to recognise the writing in this view, because it isn’t presented to you in the usual format you see it.

Introducing the Bressingham Roll

As part of our continuing collaboration with the Norfolk Record Office, we’ve recently been lent a parchment roll from a bundle in their archives (Call number PHI468,577X9)

The Bressingham Roll as open as possible. The section to the right of the image is stuck together.
The Bressingham Roll as open as possible. The section to the right of the image is stuck together.

The Bressingham Roll as unrolled as possible. The section to the right of the image is stuck together.

The roll is unfit for production in the archives, with the inner portion becoming stuck together.

End view of the parchment roll in rolled up-state.
End view of the parchment roll in rolled up-state.

The ink used in the writing contains both iron and copper, so should have good contrast in X-Ray imaging.

Bressingham Roll – Initial Results

Soon after the Bressingham Scroll arrived, we performed a quick test CT scan to determine the settings needed so we could image both the parchment and any ink on it.

A single slice of the scan is shown here, the ink shows up as brighter patches on the whirls of the parchment.

The end-on single slice view of Bressingham roll shows both the parchment and evidence of ink very clearly.
The end-on single slice view of Bressingham roll shows both the parchment and evidence of ink very clearly.

This was imaged at 30kV with a 200um Al filter and post-processing with in-house developed beam hardening correction software.

Success

In December 2011 David and Graham visited the Norfolk Archives, based in Norwich, to discuss the Apocalypto project with Antoinette Curtis and her conservation staff. To assist  in our initial scanning and virtual unrolling experiments, the Norfolk Archives graciously donated some non-accessioned objects of parchment with manuscript using iron gall ink.

One of the items is a small roll of parchment, that would be very damaging to unroll in order to read or photograph by conventional means. It is long and thin and in a damaged state that makes it impossible to unroll to read. This immediately attracted our attention, as it would be a real test of our ability to read an otherwise unreadable document.

Rolled parchment from Norfolk Archives
Rolled parchment from Norfolk Archives

The scroll was scanned in our MuCAT-2 microCT xray scanner with a 30 kV X-ray spectrum. Once the scan data was mathematically reconstructed, we could start to explore the scroll.

Norfolk Archives scroll x-ray cross-section, with an inset view of part of an inked letter.
Norfolk Archives scroll x-ray cross-section, with an inset view of part of an inked letter.

The first thing we noticed in the x-ray cross-section images is the metallic foil strip glued to the inner edge of the parchment. This shows as the bright shape at the top of the scroll in the image to the left. We can also see indications of the iron gall ink, again these show as brighter areas along the line of the parchment surface. The inset image shows a view along part of a letter on the surface. The high curvature and short depth of field of the scanned slices means that only a portion of the letter can be seen.

na_scroll1-no-parchment-crop-300x279

Volume rendering the scan data and virtually removing the parchment reveals the metal components of the scroll. Applying volume rendering techniques to the scan data and virtually removing the parchment, we can explore just the ink and metallic components of the scroll.

The lime used in the manufacture of parchment also shows up well because of its calcium content which is a metal. Excessive liming of the parchment can mask the visibility of ink in the x-ray scans; however in this case, while it shows up as a mass of spots and general noise in the image, the ink is still easily visible.

Adding back the parchment in the volume render of the scan data allows us to see the ink on the parchment. Due to the highly curved surface of the scroll, it’s impossible to read more than a few letters of a word using this technique.

The text on the rendered scroll looks faded and delaminated. This is because the distribution of iron in the ink isn’t uniform, and it’s only the iron in the ink that provides contrast in the x-ray images.

For a full unrolling, the data was passed to Oksana and Paul, our colleagues at the School of Computer Science & Informatics at Cardiff University. They will take up the story from here.

A volume render of a section of the scan data, showing ink on the outer surface of the scroll.
A volume render of a section of the scan data, showing ink on the outer surface of the scroll.