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In 2020, the Ma conservation students were given the exciting opportunity to analyse the Lincoln Charters as a part of their studies. These charters cover almost 400 years of Lincoln's history, documenting the king granting the city specific privileges: anything from being allowed to dispense justice from the Guildhall, to giving the citizens the right to hold the Christmas market in the castle. These charters haven't been examined since 1788, so they were brought to the University of Lincoln to be assessed and treated. The City of Lincoln Council is in the process of designing a new display for the charters, so it's the perfect opportunity to give them a bit of care before they are displayed. First the parchement was relaxed and unfolded, allowing it to be better analysed. The conservation students split into teams, with each team focusing on one document: here we analysed the Edward the Third charter of 1361. Analysing the Charters With this rare opportunity, each group wanted to find out as much as possible. The charters are an important part of the city's history, so none of the techniques could risk damaging the documents. With this in mind, we chose four techniques that together, give us a complete picture of the artefact, both on the surface and inside. Photogrammetry Reflectance Transform Imaging (RTI) X-Ray Fluorescence (XRF) X-Ray Photogrammetry This is a technique that helps to protect objects by reducing how much you have to handle them. It creates a digital 3D model of an object by combining a large number of photographs in specialist software. In this case we created a model of our charter that we can turn and manipulate with no damage to the original document (Taqriban, et al., 2019). Above and below are front and side views of the wax seal that is attached to the charter. The area of focus is the remains of the wax seal, featuring a seated figure. It is encased around the sides with a new wax material that was added by Samuel Lyon in 1788. Reflectance Transformation Imaging RTI is similar to photogrammetry, in that it merges a number of photographs to create a virtual object. The difference here is that each photo is taken with slightly changed lighting, which means that when the images are collated it is possible to pick the lighting direction (Yong Hwi, et al., 2016). Here the changing lighting highlights the deep creases across the charter as a result of many years having been stored while folded. X-Ray Fluorescence XRF is a technique that interacts with the sample on a sub-atomic level to identify its elemental composition. By directing x-rays at the surface, the machine causes it to release an amount of energy that is unique to the element. The results from the parchment show that the ink used on the charter is iron based. Iron gall ink was one of the most popular inks used for parchment, as it is able to hold well to the surface. It is normally made using oak galls, iron sulphate, gum arabic and water. Due to its acidity, the ink is able to "bite" into the surface of the parchment, while others have difficulty attaching well enough to be permanent. The XRF results also showed up a large quantity of sulphur. The main cause of this in old documents is sulphur dioxide from smoke produced by burning coal or oils (Bowden.& Brimblecombe, 2000). X-Ray X-rays are frequently used in conservation to work out whether an object has something hidden inside it. As long as the hidden material is more dense than the body, it is possible to detect it on an x-ray, though the results aren't always what was expected (Possenti, E., et al., 2020). Although the charter was too big to fit into the machine, the wax seal had been carefully packaged in a pouch of papers. This was small enough to fit, and had writing on most of the layers. If the ink used was iron gall ink, the metal particles would be enough to show up in the results. This was a useful technique, because the normal way of looking for that particular type of ink is a destructive method- meaning that the sample tested is damaged or destroyed. Although in this case the writing didn't show up on the x-ray, it still tells us something. To start with, it confirms that the pouch was made at a different time to the parchment, as people would often use up excess ink from one document on anything else needing to be written at the same time. Since it didn't show up on the x-ray, the pouch ink is not iron gall, unlike that on the charter. It also confirms that the pouch is made of paper. If you look closely at the x-ray above, you can see fine vertical stripes on the pouch. These are called laid lines, and they used to be formed during the production of paper. The results of the various tests confirmed many of the previous theories about the charter, while also providing some new information. The collaboration between the City and University is still ongoing, with the hope that more students will have the opportunity to interact with these fantastic pieces of the City history. If you are interested in learning more about the charters or the techniques used, here are some useful links. Lincoln Charters: Newspaper article about the Lincoln Charter conservation. Collaboration between the University and the City for the Charter. The charters were brought together for study by medieval studies students in 2016. Records of the Royal Charters and translation. Photogrammetry: Photogrammetry definition. Reflectance Transformation Imaging: Description of RTI and how it is used. Reasons for the use of RTI and examples. X-Ray Fluorescence: How XRF works. What is XRF and what are its benefits. Bibliography Bowden, D.J., Brimblecombe, P., 2000. Sulphur Distribution in Parchment and Leather Exposed to Sulphur Dioxide, Journal- Society of Leather Technology and Chemists, pp.177-186 Kim, Y. H.; Choi, J.; Lee, Y. Y.; Ahmed, B.; Lee, K. H., 2016. Reflectance Transform Imaging Method for Large Scale Objects, 13th International Conference Computer Graphics, Imaging and Vizulisation Taqriban, R. B.; Ismail, R.; Ariyanto, M; Yaya, S. P.; Andika, F., 2019. 3S Model of Photogrammetry Technique for Transtibila Prosthetic Socket Design Development, 2019 International Seminar on Research of Information Technology and Intelligent Systems, pp 256-462 Possenti, E.; Conti, C.; Gatta, G. D.; Merlini, M.; Realini, M.; Colombo, C., 2020. Synchrotron Radiation µ X-Ray Diffraction in Transmission Geometry for Investigating the Penetration Depth of Conservation Treatments on Cultural Heritage Stone Materials, Analytical Methods vol 12, pp1587-1595 Written by Megan Linford. Photos and digital artefacts produced by M. Linford, Y, Lindars, R. Fenn and L. Johnson.