Held within the hallowed halls of Parliament House lies a treasure: a 1297 issue of the Magna Carta.
Australia’s issue has been on display and well-protected in a CSIRO-built preservation case for 60 years.
Back in 2016, the Department of Parliamentary Services called upon conservators at the Grimwade Centre for Cultural Materials Conservation.
Charged with opening the case and learning more about the materials that make up the document, then returning it to display, the conservators conducted their work meticulously over eight years.
Coming full circle from engineering the original case, conservators asked CSIRO material scientists to try to work out the medieval dyes used on the document’s silk cords.
It’s a tale for the ages, merging history, art, engineering, science and a bit of botany.
Australia’s Magna Carta is now back on public display in a new and improved case, ready to be marvelled at by generations to come.
So, what has been learned from the years of meticulous conservation and in particular what did the silk cords tell us?
History 101
Before we get to the science, let’s start with a bit of history.
The Magna Carta is one of the most well-known documents – not just because of what’s in it, but because of what it represents.
The Magna Carta or ‘Great Charter’ was issued in June 1215 by King John of England. At the time, he was trying to put an end to a baron-led revolt. A charter back then was just a formal way of granting rights or property.
Kings before John, such as Henry I, Stephen and Henry II, had issued charters, known as ‘coronation charters’, promising to stick to certain rules and traditions. In fact, the barons who forced King John’s hand pointed to Henry I’s charter as a reason why he should agree to theirs.
For starters, it introduced the powerful idea that no one – not even the king – is above the law. Some key legal principles we take for granted today, such as due process under the law and trial by jury can be traced back to parts of the Magna Carta. It also played a role – albeit a complicated and slow one – in shaping parliamentary democracy.
Over the centuries, its influence has gone far beyond medieval England. Ideas from the Magna Carta are reflected in major documents such as the 1789 Declaration of the Rights of Man in France and the United Nations’ Universal Declaration of Human Rights in 1948.
Australia has the Magna Carta?
Well, we have a Magna Carta. Back in 1952, Prime Minister Robert Menzies made a big announcement: The Australian Government had bought a 1297 Inspeximus issue of the Magna Carta for the nation.
The Department of Parliamentary Services explains:
The 1297 Inspeximus issue of the Magna Carta owned by the Australian nation is an official charter sent in Edward I’s name for public proclamation. The term inspeximus means that the King had inspected and confirmed the great charter of his father Henry III. It closes with an admonition that the charter be observed in perpetuity. It was witnessed by Edward’s son (later Edward II) at Westminster during the King’s absence campaigning in Flanders. It was originally accompanied by the reissued ‘Charter of the Forest’, now held by the British Library, which established access to the royal forests for ‘free men’.
Sealed with science
During the 1950s and early 60s, CSIRO researchers were asked to design a display case similar to the one that had recently been built in the US to protect the American Declaration of Independence.
An engineering challenge of some magnitude, the end result was an argon-filled enclosure intended to control sources of chemical degradation. The case also featured a transparent, yellow-coloured filter over the top of the container to reduce ultraviolet light exposure.
The case certainly stood the test of time and protected the Magna Carta until 2016 when it was removed from display and conservators carefully deconstructed the case piece-by-piece.
Decoding history using materials science
Once released from its casing, the Department of Parliamentary Services team worked with conservators from the Grimwade Centre for Cultural Materials Conservation to analyse the document. Identifying the materials, inks and dyes used to produce the Magna Carta would help the conservators determine the best conditions for its ongoing preservation.
The best way to preserve documents such as the Magna Carta is to keep them in the cool, dry and dark, but then Australians would never be able to see this important piece of history. The amount of light, UV levels, humidity, temperature, contaminants and oxygen all play a role in the aging of artefacts. The requirements can also differ depending on the materials being preserved.
So, to ensure the Magna Carta is displayed in the best possible conditions, the conservators needed to identify all the materials that form this precious document.
Peering into the past
Based on historical data, conservators used a diverse range of analytical techniques to confirm their understanding of the document’s materials. This included confirming with X-ray Fluorescence (XRF) that iron was in the ink – confirming it to be iron-gall ink – and using mass spectroscopy to identify the parchment as sheep skin.
The silk cords attached to the wax seal were more of a mystery and where the real fun starts – for CSIRO anyway.
While the silk most likely originated from Europe or Asia where silk industries and trade routes were well established, determining how it was dyed was key.
Digital microscopy identified that the cords were produced using a technique called finger-loop braiding with slightly different techniques being used for the red and green cords. To gain further information, including confirming the cords are silk, seeing the condition of the fibres and identifying the dyes, required samples to be taken.
Dyeing to make the cut
Cutting even a small strand from the Magna Carta’s silk cords for testing was a big decision for the document’s custodians but it was the only way to undertake the analysis. Two tiny samples were cut from each of the frayed ends of the cords using micro-scissors and working under a microscope.
The two samples measured only eight and 12mm.
Individual fibres from the samples were used for polarising light and scanning electron microscopy, which confirmed the fibres were silk, and found they were remarkably fine and in an excellent state of preservation.
The remainder of the samples were handed over to CSIRO to identify the dyes.
Building a dye library
To work out what dyes could have been used on the Magna Carta’s silk cords 700 or more years ago, we needed a library of potential options to compare the silk cord dye to.
From historic research and surviving recipes, conservators knew the dyes commonly available at the time this inspeximus Magna Carta was issued. This allowed them to produce a short list of the most likely dyes for a reference library of dye samples to compare the dyes found in the samples of silk cords.
The green cords would have been made by combining yellow and blue dyes.
The plant material for the dyes was sourced from overseas or grown locally to produce solutions and samples of silk dyed using medieval techniques.
The medieval dye library:
- Yellow dyes – three welds, calendula, Anthemis tinctoria, tansy,
- Blue dyes – two woads and two indigoes
- Red dyes – two different varieties of madder.
Lifting the [silk] veil on the science of extraction
Before CSIRO scientists could analyse the Magna Carta silk cord samples, they turned their attention to mastering the extraction process using samples from the silk library.
As some plant dyes bond differently to silk than other materials, scientists used two extraction methods on samples from the silk library – formic acid and dimethylformamide (DMF).
It was important to ensure that the modern silk used in the silk library would be comparable to the Magna Carta’s silk. Plant dyes were used for many centuries until synthetic dyes were invented in the 19th century. Conservators provided a sample of 17th century Dutch or Italian yellow silk, which the scientists used to confirm that the methods they intended to use to extract the dye worked on both modern and historical silks.
To extract the dyes from the test silks, scientists used the same amount as they had of the Magna Carta’s silk – two 4mm and two 6mm long strands (each of the samples needed to be halved to enable the separate extraction techniques).
The CSIRO team was worried that such small samples would significantly limit their chance of getting results from these test silks.
But… it worked! Using weld on the 17th century silk, scientists were able to extract and identify the plant.
Next, and with one shot only, the scientists halved the Magna Carta samples and extracted the dye.
Small sample, big effort: what could – and couldn’t – be found
CSIRO scientists used ultra-performance liquid chromatography (UPLC) to investigate each extracted dye. This technique takes the extract and separates it into its chemical components, which are displayed in a chromatogram. Each dye is made up of tens or hundreds of different compounds with the specific mix unique to a plant type, showing up as a ‘fingerprint’ made up of the peaks of the chromatogram.
Peak matching
Employing fingerprint – or peak – matching techniques for chromatograms between the reference dyes and the green Magna Carta silk cords silk, scientists found one of the yellow dyes – weld – detected.
The yellow dyes were not detected in the red silk. The blue dyes – indigo and woad – and the red madder dyes were not detected in either silk.
Nicola Spencer is one of CSIRO’s analytical chemists who worked on the silks.
“The challenge of extracting even the faintest traces of dye from these tiny 700-year-old samples was immense – like finding a needle in a haystack. Yet, we not only detected a dye in one of the silks but have also pioneered a new analytical capability for CSIRO,” Nicola said.
While CSIRO’s science team was amazed they could match one dye, they’re also disappointed they couldn’t find out more. So, what does ‘not detected’ mean in this situation? It could be the result of a number of things:
- The dyes in the medieval reference library were not used to dye the Magna Carta silk.
- The age of the Magna Carta silk sample meant that the dye was present but couldn’t be extracted effectively.
- The dye compounds on the silks had chemically changed over time through exposure to environmental factors such as air and light.
- The reference dye samples were not the same as the dyes used in medieval Europe. The team was comparing silk dyed with plant material grown in the 21st century in Australia or overseas. There are likely many variables that have changed over 700 years in both the plants/seeds and the soil, water and environment.
- There was just not enough for CSIRO to work with! The sample scientists were working with was tiny, so the amount of dye able to be extracted may not have been enough to measure.
What’s next
The Magna Carta is now back on display at Parliament House in Canberra, protected in its new preservation and display cases. The conditions inside the case are designed to make sure that this important document, with its beautiful silk cords, were the best that science could achieve.
CSIRO still has all the data from each extraction. So, scientists will continue to build up the medieval dye library to see if they can make any matches.
They will also continue to develop this analytic capability, which is unique to CSIRO, and see how they can use these new methods to learn about other historical artefacts.