Transcript of presentation given by Josep Grau-Bové at joint National Heritage Science Forum (NHSF) and Icon Heritage Science group events to scope the networking and career development needs of heritage science students and Early Career Researchers, March 2021
That was the title of my presentation. We are here because we are heritage scientists. What does it mean, to be a heritage scientist?
We have the fortune and the misfortune of giving shape to a new field of science. Because heritage science is new, in many ways a 21st century science, and in many other ways, it is old, as old as curiosity.
If you chart the history of the scientific study of heritage, do you know what you will find? You will see that every time a new scientific method is invented, someone has the idea to point it at a work of art. It happened with the microscope, the synchrotron, structural simulation, pollutant monitoring, everything.
We are here because we share this fascination. This ancient magnetic attraction. However, while the curiosity of heritage scientists has been here forever, the field is new in other ways.
It has been in the last decade that we have come together, in academic journals, in conferences, in research programmes, in the eyes of government funding, in representative bodies such as the NHSF and ICON HG. And when we come together, we discover that there are links between our isolated individual curiosities. We share questions, and problems. And it that sense, we are a new science, that is just discovering its questions and its problems.
I like to think a heritage scientist is like a Hobbit. Humble, brave and stubborn, an explorer that always remembers home. Humble because in our field, we always need the expertise of others. Collaboration depends on admitting that we don’t know all the answers. Brave because you need to be crazy to step into the unknown, in an area where we’ll spend most of the time out of your comfort zone. An area where the future job market depends on our collective success. Stubborn because there are no established ways of doing things. We need to make our own way, and stick with it.
And finally, also like a hobbit from the shire, it doesn’t matter how far we go from our initial training, all heritage scientists remember who they are: chemists, conservators, architects, psychologists, engineers, art historians, social scientists – and this identity defines how we work.
“Heritage Scientist” is not a permanent identity. Many are not heritage scientists forever. And that’s another strength of our field. Some of the best heritage scientists I have met, have also made contributions outside of heritage. Most of us have come to heritage after degrees or even PhDs that had nothing to do with it. Some of us will move on to tackle other problems. This diversity of interests is common. It is even necessary. Because how else can we study such a complex array of scientific problems?
The question is, while we are here, how shall we organise ourselves? Solving this riddle has two parts. One is how we organise our ideas. We cannot solve this one today. That will require 10 years of discussion. The other part is how we organise our conversations as a group. This is the one we want to brainstorm today. The scientific ideas will naturally follow.
The Strategic Framework for Heritage Science in the UK is built around an outcomes framework and one of its three high-level goals is “A skilled and diverse heritage science community (workforce and volunteers) that is well placed to respond creatively to future change”.
At NHSF, our Communities working group focuses on delivering against the underpinning outcomes that will help to achieve this goal. It brings people together from across its member organisations to pool their strengths, knowledge and networks to address shared challenges in the sector.
In March 2021 we worked with the Icon Heritage Science group to run two workshops to scope the networking and support needs of heritage science students and early career researchers. For NHSF, these workshops are a step towards the strategic framework outcome of ‘Recognition of heritage science as an attractive career’. They also build on findings of research commissioned in 2017 to understand some of the opportunities and constraints associated with a career in heritage science (which highlighted the need for networks to strengthen the identity of heritage science, and a platform to enable young professionals to interact, share challenges, and develop skills).
We wanted to ask heritage science students and early career researchers about the support they need to pursue a career in heritage science and so our two online workshops included introductions to the work of NHSF and the Icon Heritage Science group, a reflection on heritage science as a culture and a career (see our next blog post for more on this) but for the most part, the sessions focussed on facilitated discussion groups asking:
– What are the needs of heritage science students and ECRs?
– How can NHSF/Icon Heritage Science group or other bodies help to address these needs?
– What are the next steps for the heritage science community?
Forty-eight people took part in the two sessions and contributed thoughtfully, enthusiastically and constructively to a wide-ranging conversation about what is needed and how it might be provided.
What did people identify as needs?
The post-it record of the breakout groups is shared below, and overall the main needs can be summarised as:
Knowledge of who’s doing what and where (a directory?) – to help develop a picture of the broad heritage science landscape, support making research connections and building networks.
Mentorship and help understanding career pathways and opportunities.
The opportunity to present projects and research and hear about work by others.
Training opportunities focused on specific (technical) topics.
Case studies of how people have entered the field and their career pathways.
A source of information on job posting and training opportunities.
Both NHSF and the Icon Heritage Science group are now working out how we can best provide support.
From NHSF’s perspective, we have some things in place already that address some of the needs, for example:
Next, we’ll work with the people who have signed up to stay in touch on this topic and help us address the identified needs. High on the list will be agreeing which platform will work best to support the information-sharing and networking.
Heritage Science is the use of science and technology to understand and care for cultural heritage, and support engagement or interaction with it. As we’ve shown in the blog posts over British Science Week 2021 heritage science can take many different forms such as using powerful microscopes, 3D laser-scanning, x-rays and more.
We’ve been looking at examples of how these wonderful techniques and technologies can be used in learning programmes aimed at school-age children and are starting to share some of the examples we’ve found on our website here.
Our final blog for this year’s British Science Week highlights these resources in the hope that it will inspire you to let us know of other examples that you know about. Over time we want to create a resource that shows how heritage science can support many different parts of the curriculum – and share our enthusiasm for the #HeritageScience with teachers and pupils.
Heritage Science at The National Archives Activity Pack
The National Archives has created a family activity pack for home and in the classroom to showcase the heritage science and conservation research happening in their Collection Care Department.
The activity pack was developed by the Collection Care and Education teams to celebrate British Science Week 2021. The intention of the pack is to act as a gateway to showcase heritage science and conservation research happening behind the scenes at The National Archives in an accessible way. In the pack you can find two activities: ‘How to Make Berry Ink’, where children can learn how to make blueberry ink and ‘How to Make Invisible Ink’, where children can learn how to send secret messages using lemon juice. It is hosted on their family activities webpages and is designed for home and the classroom.
Outdoor archaeological learning
Forestry and Land Scotland has created an Outdoor Archaeological Learning portal to encourage young people to be inspired by Scotland’s rich cultural heritage and historic environment. It includes a collection of resources, articles, and activities to encourage place-based learning. They are designed to be used by teachers, youth group leaders and archaeological educators. Through asking young people to record, discuss and interpret an archaeological site, the resources help them develop critical thinking skills, creativity, confidence, and teamwork skills. Resources are available on various archaeological topics including: Dendrochronology; Recumbent stone circles; The Picts; The First Foresters; Dun Deardail; and Into the Wildwoods. Access the resources here.
Go Forth and Discover! Digital game
A downloadable game- based learning activity has been developed from 3D digital documentation of the historic Forth Bridges to educate school children about their construction. The activity was created to match the social studies curriculum taught in Scottish schools and was designed by the Centre for Digital Documentation and Visualisation LLP (a partnership between Historic Environment Scotland and The Glasgow School of Art). You can access the freely available game here.
Do you know of any other examples of heritage science being incorporated into learning programmes for children of school age? Please add them to our online noticeboard here.
We will also continue to add new case studies to our website. Look out for them here.
Our next blog for British Science Week 2021 is brought to you by The National Archives which has created a family pack for use at home and in the classroom to showcase the heritage science and conservation research happening in their Collection Care Department.
This activity pack was developed by the Collection Care and Education teams to celebrate British Science Week 2021. The intention of the pack is to act as a gateway to showcase heritage science and conservation research happening behind the scenes at The National Archives in an accessible way. It is hosted on The National Archives’ family activities webpages and is designed for home and the classroom.
In the packs you can find two activities: ‘How to Make Berry Ink’, where children can learn how to make blueberry ink and ‘How to Make Invisible Ink’, where children can learn how to send secret messages using lemon juice. The activities include recipes, instructional videos, and accessible PDF instruction posters.
The resources also highlight documents found in The National Archives’ collection that link to the packs to show how scientific analysis can help to understand the materials that the documents are made from and increase the artefactual value of the collection. The linked documents include the spectroscopic analysis of a Tudor map, to better understand the painting techniques, use of colour and materials deployed by Tudor mapmakers; analysis of wool sample books where scientists are analysing the dyes in the wool samples contained in the books to learn more about historic dying practices (with the future hope of creating a reference database using the recipes included in the books and accompanying spectral information); and the ‘orange juice letters’, letters written by the Gunpowder Plot of 1605 conspirators who used orange juice as invisible ink. Here, we have explained how multispectral imaging can help increase the readability of these documents.
For many children learning about historic documents this will be their first introduction to scientific research in an archive. The National Archives hopes that through these fun activities, and the accessible blogs that accompany them, children and their families will learn about a different area of study within archives and be inspired to learn more about heritage science.
The expansion of remote access to microscopy equipment at the Natural History Museum is the subject of this post from Professor Aviva Burnstock of the Courtauld Institute of Art. The British Science Week theme of #innovation is evident in the resilience and enthusiasm of staff and students from both organisations.
The Courtauld has for decades maintained a fruitful collaboration with the Natural History Museum (NHM) for research on painting materials and techniques and evaluating methods for the conservation of paintings. We have relied on regular access to scanning electron microscope (SEM) imaging and elemental analysis for the examination of paint layers and high-resolution imaging and characterisation of inorganic pigments that cannot be identified using other methods. Lockdown presented major challenges for access to these vital resources, equipment and expertise. Alex Ball and Innes Clatworthy from the Natural History Museum have worked tirelessly to provide our staff and students remote access for electron microscopy including training and support. Now we can, following current Covid safety regulations, deliver our samples to the NHM and book a remote session on the equipment, undertaken through our lap-tops from the comfort of our homes. Support for this process has inspired the current generation of students, many of whom come from fine arts and humanities backgrounds to do the high-level scientific work that is essential for the conservation of paintings even in these most difficult times.
“With the initial guidance (and patience) of Innes, the remote control of the SEM machine felt very similar to using the system in person at the NHM. The screen resolution was clear, the connection was good and it was easy to save and access files, I just need to remember how to use all the buttons!” Megan Levet graduate student in Conservation, Courtauld Institute of Art
“It was really amazing and slightly surreal to be able to use the equipment from my house. Innes was super helpful and made the process seem easy and straightforward. I look forward to making the most of this facility in the near future”, India Ferguson graduate student in Conservation, Courtauld Institute of Art.
“I didn’t expect to be able to begin using SEM EDX at this time when so much is restricted. I was unsure how the analysis would work remotely. With the support of Innes at the NHM accessing the software was straightforward; once the sample was in the chamber it was almost as good as being there. Beautiful images of a painting cross section were streamed to my laptop and analysis could be performed simply by pointing and clicking on a chosen area. I look forward to using this powerful tool to support my work in the near future!” Jack Chauncy, graduate student in Conservation, Courtauld Institute of Art
Written by Aviva Burnstock, Professor of Conservation at the Courtauld Institute of Art
This post continues on from our last post ‘Back to the Future’ which explored how the Natural History Museum developed remote access to some of its laboratory equipment during lockdown. Here, Dr Joyce Townsend from Tate, describes her experience of using the equipment from home.
As I spend another groundhog day at home during the third lockdown and imminent first anniversary of the Covid-19 pandemic, remote access for running instruments at the Natural History Museum (NHM) seems like a concept that was developed just in time. I’ve been an electron microscope user and driver at the NHM for some 10 years now – certainly long enough to have used 2 or 3 models of variable pressure SEM (scanning electron microscope), two software packages, and three operating systems. My samples consist mainly of paint fragments on self-adhesive carbon stubs, interspersed with larger and more complex paint samples mounted in resin blocks and exposed as cross-sections, and a few outliers such as canvas, metals and plastics. Since they come mainly from artworks, anything large enough on the stub to spot by eye in a good light – provided such a small specimen is also representative – is the right size for SEM-EDX. I do sometimes seek assistance with imaging of canvas, or newly-applied and solvent-rich paint (high vacuum would make short work of its topography!), but in most cases I am more interested in elemental analysis to prove or disprove identifications of inorganic pigments and extenders from optical microscopy, and sometimes to reveal unexpected elements. High-resolution imaging is not usually my aim for many samples. A knowledge of historic pigments used in the west, and of a great variety of historic manufacturing processes, enables good inferences to be made about the compounds in the samples, in nearly all cases. My samples are at least fairly robust, and there are no issues with shelf life or storage temperature, as I deliver them to a masked figure emerging from the premises on freezing mornings.
My fellow conservation scientists and all my other colleagues with humanities backgrounds were vastly impressed when I announced, ‘If you can control a Mars rover from Houston, Texas, you can surely drive an SEM from across central London’. Then I wondered whether Tate systems would ever communicate seamlessly with NHM systems. The set-up was lengthy and took a day of effort, and the process of logging in through two opposing firewalls is never fast – but it does work. I have always established the connection from my usual workplace whilst logged into both systems, which makes for a complicated workspace on a large single screen. It does enables instant storage of the snipped or screenshot spectra and locator images into PowerPoint format on our own system, ready to be dropped into artwork reports and interpreted with other data. This data capture is far more time-efficient that the different workflows I have used in the NHM processing lab over the years. There’s an additional big advantage in being able to access other data and artwork information instantly through the Tate system whenever I need more sample information, which cannot be done in South Kensington without hogging a number of workstations at one time to make it possible.
Running the SEM remotely now works very smoothly, in fact. This month I have used it for two full days. The JEOL IT500 has clearly been designed for the purpose: its stage movement and auto functions for focussing and brightness/contrast make it far more possibly to drive the SEM from one keyboard and no joysticks than it would have been for earlier models. It helps to pre-plan the sample holder map to include groups of samples of the same height and stub size, and to ask for large groups of samples to be placed on the larger holder that fits in the chamber. The filament may still occasionally fail in the midst of analysing the most interesting sample of the day, but the support team is on call (now by Teams as well as e-mail and mobile) and they will replace it and refocus to average sample height. Remote training for new users must be more challenging for them, but that sounds perfectly feasible too.
Written by Dr Joyce H Townsend, Senior Conservation Scientist, Tate
Our next post for British Science Week 2021 is from Dr. Alex Ball of the Natural History Museum. His post focuses on the challenges and opportunities presented by a move to provide remote access to laboratory equipment during lockdown.
In the (almost) 30 years since I joined the NHM as a PhD student, the one constant has been that the electron microscope labs were a resource that you had to book in advance and physically turn up to use your session on the microscopes. SEM sessions were typically a half day at a time before you had to give up the microscope to the next user, or perhaps you’d get lucky and were able to work on until the end of the day. The rules were simple, you could have two sessions booked in advance and you could book another session once the first session had started.
We worked like this to prevent users from block booking a microscope for days on end as everyone deserved an equal chance on the instruments.
As the equipment got more and more sophisticated and could be programmed, it was not unusual for users to set up programmed imaging or analysis sessions to run overnight, or even over the whole weekend if enough samples could be loaded and programmed in advance.
A very few, experienced users were authorised to work late and even to come in at weekends, under the proviso that if anything went wrong, they had to follow their training, switch the instrument to a safe mode, let the staff know what had happened and then go home.
Then in March everything changed.
With just a few days’ notice, the Imaging and Analysis Core Research Laboratory (IAC) staff had to place the whole laboratories into some sort of safe mode, shut down instruments where possible and arrange to leave the labs, for weeks, months, who knew? Instruments that had never been shut down for more than two days were suddenly idle. Would they restart? Could they be reanimated? No-one knew.
A few staff came in one or two days a week to check for problems and to ensure that all was well, but apart from that, the corridors were dark and silent. The scene more like a science fiction horror movie set than the bright and lively place we were used to.
When we finally returned, a few at a time, we had the mammoth task of restarting all the instruments, testing and recalibrating, booking in missed service visits, fixing stuff that had failed and then figuring out how to make all of this kit accessible again.
Throughout lock-down we’d been attending remote conferences and the question everyone was asking was “How do we get back to work safely?” The community spirit in those meetings was really encouraging. The first meeting I attended included participants from all over the world, including the USA, Portugal, France, Germany and Australia to name a few. Solutions came thick and fast, so we weren’t having to go it alone, we could ask each other for advice and for help.
For the Electron Microscopy unit, this gave us the confidence to try something we had never allowed in the past and in fact had not even really contemplated: remote access to the instruments. Starting from what we’d learned and discussed with other labs and with the NHM’s IT team, we set up the instruments to allow remote desktop access and then set to work testing and practising. First from one computer to another in the same room, then from an office to the SEM (scanning electron microscope) within the lab and then finally with one staff member at home and another providing support in the lab.
At each stage we documented our findings, worked out safe ways to work and moved on. As soon as the financial accounts reopened we ordered new sample holders, so that instead of loading six or eight samples, we could load 25 or 50. We were no longer planning to confine users to half a day, but contemplating sessions lasting 2 days or more.
Finally, after about two weeks, when we felt that we’d completed enough testing, we started to reach out to the users. We had our priority user list provided by Science Group and so we set about contacting them, scheduling training, acquiring samples, or planning for samples to be prepared. We trained a few of them to safely use an instrument from their home office, how to control a microscope which was normally controlled with two joysticks and a complex control panel with just the mouse and keyboard they had. We simplified the user interfaces so that instead of two screens, they only needed one.
Samples get dropped off in the IAC corridor, or are collected from offices and are quarantined for a few days, photographed and then put aside until needed, or sent across to the newly reopened mineral prep labs for preparation.
Every case seemed to be different. What was the minimum network speed required to control the microscope, move the sample and focus the image? How did we control two different computers from a single laptop so that we could operate both the SEM and the EDX system? How did we accommodate Apple users? Could we allow external users remote access to the instruments?
For the past few weeks, we’ve been reinventing the labs. It’s clear that the relationship between the users and the staff has changed. Remote training has proven to be surprisingly easy, provided the network connection is good and Teams or Windows Remote Assistance is playing nicely. On the flipside, when things go wrong, it can take days for us to find the solution.
We are finding users can fit their instrument sessions in around their lives in lockdown, so being able to load one to two days’ worth or samples is a huge advantage. Not everything works and patience is required, but we’ve found that it’s just about possible for us to supervise two or three users.
Our users are also processing their data remotely. Not only have they been accessing the instruments, but they’ve been accessing the workstations remotely as well. The micro-CT lab led the way in this by opening up their workstations right from the beginning of the lock down. We also have to give the instrument suppliers credit for being so willing to work with us and advise us on how best to manage this and also for making some pretty expensive pieces of software available to home users right through to the end of September.
We have so few active users at present, but we feel just as busy. Meeting someone you haven’t seen for months in person is a shock, but also a welcome distraction. There are still people I am working with that I’ve never met, other than from the other side of a webcam and screen.
There’s a lot of work still to complete and I have a lot of concerns over how we are going to teach the next generation of microscope users. Some people I’ve worked with over these past two months haven’t even seen the instrument that they’ve now spent days using.
This new way of working is making me wonder what the future will be like. Will some of our visitors be able to access instruments remotely, so removing the need for them to come to the Museum at all? Could this usher in a new era of accessibility for those who would normally not have the money or opportunity to travel to the UK and to access these lab facilities?
What are the security implications for our instruments and network?
How do we get data to users, remember the files can be really large and how will they process them? What additional hardware do home users need to work effectively? At work I use two screens. At home I have the luxury of a decent sized screen, but many are working just from a laptop screen. Remote support for us has heavily relied on mobile phones, headsets and webcams. Teams, Whatsapp and even plain phone calls have all played a role in getting connected and supported.
There is a new initiative, “The Future Ways of Working” which will be looking into this for the future, but it’s clear that a lot of these solutions need to come sooner rather than later. For now, if users need access, we do our best to make it happen.
Written by Dr Alex Ball of the Natural History Museum.
Our next blog post for British Science Week 2021 comes from Dr. Moira Bertasa, Research Assistant in Laser Conservation Science in the Department of Scientific Research at the British Museum. She describes new research to find a safe way of cleaning feathers with lasers.
The British Museum collection includes many objects made with bird feathers. This includes featherworks from South America and Oceania, but also more unusual objects such as a Victorian necklace with iridescent heads of humming birds and a Chinese snuff-bottle made with blue kingfisher feathers inlaid in silver (Figure 1). Cleaning feathers can be very difficult. Over time, they become brittle and traditional conservation cleaning methods such as gentle vacuum cleaning, brushing or solvent cleaning are unsuitable as they risk damage to the object.
In such situations, conservators and scientists join forces to explore new conservation techniques. I am a conservation scientist. In these years, I had the opportunity to explore a broad range of subjects from the study of innovative cleaning methods to remove stubborn stains from the artwork to the preservation of graffiti artworks. Currently, I am working with conservators at the British Museum to investigate the application of lasers to clean feathers. Laser radiation was found (by accident!) to be highly effective at removing black encrustations on marble facades while conducting holographic measurements in Venice in the 1970s. Since then, laser cleaning has become an established conservation method to clean stone and ceramics and it has been used at the British Museum since 2002. (To find out more about the Museum’s experience with laser cleaning, have a look at this short video)
Laser cleaning is a non-contact method, which makes it very useful for fragile artefacts, such as feathers. However, laser radiation can also cause serious damage to objects if the laser parameters are not carefully selected. For instance, at a high fluence (which is the energy of the laser per m2), it makes small holes in feathers, something that the conservators definitely want to avoid! This is why I do not test lasers on feathers from museum objects. Instead, I am currently testing our Er:YAG laser (Erbium-doped Yttrium Aluminium Garnetlaser) on pigeon feathers collected during a walk in my local park (Figure 2). This way, I can select the appropriate laser cleaning parameters without worrying about causing damage to museum artefacts. I have just started my research and, in collaboration with conservators, hope to determine an effective and safe laser-cleaning procedure for feathers.
Written by Dr Moira Bertasa – Research Assistant in Laser Conservation Science in the Department of Scientific Research at the British Museum (firstname.lastname@example.org)
M. Cooper and J. Larson (1998). Laser Cleaning in Conservation: An Introduction. A Butterworth-Heinemann Title
Written by Lucia Burgio, Senior Scientist, Victoria and Albert Museum
As part of NHSF’s contribution to British Science Week 2021 we’re sharing examples of heritage science from a range of different organisations. This blog post features work at the V&A, with help from the Natural History Museum and the National Gallery.
What do you do when a rare museum object suddenly springs a surprise on you? Easy: you investigate, and then call in the cavalry.
This is exactly what happened at the Victoria and Albert Museum with a seventeenth-century South American table cabinet, the first object of its kind on display in a UK public collection (Fig 1).
Why was this table cabinet unique? Because it was made using materials and techniques centred around mopa mopa, an indigenous resin from the Andes. The traditional method of preparation of this resin involves chewing it as if it were bubble gum, stretching it and applying it on the surface of objects. The result is a lacquer-like finish, glossy, beautiful and very, very durable.
The scientific investigation at the V&A produced the first bombshell: the white pigment used everywhere on the cabinet was calomel, mercury(I) chloride. In the past calomel was well known as an alleged medicinal remedy for all sorts of illnesses, from syphilis to constipation. But as an art material? Certainly not. What a discovery! We re-christened it ‘mercury white’.
The second bombshell fell when we X-rayed the object: a grim reaper suddenly appeared on the lid (Fig 2) – this must have been painted on the object first, and then covered in the second half of the 20th century with a less frightening decorative scheme.
Enter the cavalry: I picked up the phone and called our friends at the Natural History Museum, across the road.
Full disclosure: the largest cultural heritage institutions in the UK have their own dedicated team of scientists, who can rely on many pieces of in-house scientific equipment. But no single institution has every possible type of scientist and kit, so we rely on one another to lend a hand (or type of expertise, or equipment) when the need arises.
And so it was that the mopa-mopa cabinet went for an outing and crossed the road to undergo a micro-CT scan at the NHM. The results were jaw-dropping: the hidden, original scheme was revealed. Our NHM colleagues also verified the crystallinity of the calomel on one of our samples, using their micro-X-ray diffraction equipment.
It was then time to call other colleagues, this time at the National Gallery, and get their help and equipment to map the distribution of mercury white within the hidden scheme. Lo and behold, the grim reaper, with its bits and bobs, had indeed been painted with mercury white too (Fig 3).
Moral of the story: when there is a good relationship between different heritage institution, and capacity can be found to help each other out, the results can be very rewarding. Together we can unlock the secrets of the objects in our collections, understand more about their materiality, history and context, and have the tools to care for them and preserve them for the enjoyment of present and future generations.
Burgio L., Melchar D., Strekopytov S., Peggie D.A., Melchiorre Di Crescenzo M., Keneghan B., Najorka J., Goral T., Garbout A., Clark B.L.; Identification, characterisation and mapping of calomel as ‘mercury white’ a previously undocumented pigment from South America, and its use on a barniz de Pasto cabinet at the Victoria and Albert Museum, (2018) Microchemical Journal, 143, pp. 220-227. https://doi.org/10.1016/j.microc.2018.08.010
The paper discusses the use of in-situ micro-Raman spectroscopy for the identification of calomel – a mercury (I) chloride mineral with formula Hg2Cl2 – as a white pigment in a 15th-century English manuscript and a late 16th-century portrait miniature by renowned limner Isaac Oliver, both belonging to the Fitzwilliam Museum in Cambridge, UK.
Although mercury chloride compounds have been employed for centuries in different fields including medicine, electrochemistry and cosmetics, the deliberate use of calomel as a pigment has been identified only recently within a few 17th-century South American objects. The present research, however, attests the first-ever verified presence of calomel within the original painting palette of two Western European works of art, predating its documented use in South America.
With ever-increasing possibilities to undertake non-invasive analyses of museum objects, it is quite possible that in the near future, calomel will no longer be considered an unusual pigment but rather will take its place as an integral part of the palette used by artists in different times and places.
The research behind this paper has been financially supported by the Cambridge Humanities Research Grants scheme, the Zeno Karl Schindler Foundation and a Short Term Mobility grant from the Italian National Research Council (CNR).