Cleaning feathers with lasers: a new challenge for scientists and conservators at the British 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.

Figure 1 – Hawaiian feather cape (Oc1944,02.2109), Victorian necklace (1993,0205.1)
and snuff-bottle (1936,0413.78). © The British Museum

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 Garnet laser) 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.

Figure 2 – Laser cleaning on different feathers and close up on a pigeon feather showing the holes (Ø 2mm) caused by the laser beam.

Written by Dr Moira Bertasa – Research Assistant in Laser Conservation Science in the Department of Scientific Research at the British Museum (

Further reading

M. Cooper and J. Larson (1998). Laser Cleaning in Conservation: An Introduction. A Butterworth-Heinemann Title (in Italian)

New evidence for the intentional use of calomel as a white pigment

The paper “New evidence for the intentional use of calomel as a white pigment” is co-authored by Mila Crippa, Stefano Legnaioli, Christine Kimbriel and Paola Ricciardi. It is now published in the Journal of Raman Spectroscopy and is available in open access thanks to an NHSF Gold Open Access grant.

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).

(Left) Full-page image and detail from the so-called “Fitzwilliam Missal” (Cambridge, Fitzwilliam Museum, MS 34, fol. 138r, York, England, ca. 1470) with coloured dots indicating where Raman analysis was performed; (Centre) Raman spectrum obtained from the white areas analysed on both objects (black line) and reference Raman spectrum of commercially available Hg2Cl2 (red line); (Right) full image and detail of the portrait of an Unknown Lady by Isaac Oliver (Cambridge, Fitzwilliam Museum, FM 3868, England, ca. 1596-1600) with coloured dots indicating where Raman analysis was performed. Image from:

Archaeology has no relevance….

Archaeologists are increasingly under pressure to demonstrate that their work has impact beyond the discipline. This has prompted some archaeologists — and in particular, environmental archaeologists and palaeoecologists — to argue that an understanding of past environmental changes is essential to model future outcomes in areas such as climate change, land cover change, soil health and food security. However, few archaeological studies have explored how to put research results into practice. 

Film showing the historic intensive agricultural system at Engaruka, Tanzania.

The EU-funded Archaeology of Agricultural Resilience in Eastern Africa (AAREA) project ran from 2014–2018 with the aim of looking at the long-term sustainability of two east African agricultural systems (Engaruka in Tanzania and Konso in Ethiopia). This was undertaken through a combination of archaeological, geoarchaeological, archaeobotanical and modelling techniques with the aim of providing a frank and realistic appraisal of the role archaeology can play in sustainability debates worldwide. The findings on the applicability of archaeological research were published through the generous funding from the NHSF Gold Open Access grant in Internet Archaeology in the article ‘Archaeology has no relevance’.

Figure 1 Konso terraces (1)Archaeological investigation of historic terracing in Konso, Ethiopia reveals the importance of valley-bottom sediment traps (Image: C. Ferro-Vázquez, et al. Journal of Environmental Management 202 (3): 500-513).

Admittedly, the title of the article might seem to imply our findings indicated that archaeology doesn’t have a role to play in the global conversation about sustainability, whilst in fact, the insights we gained showed that it was far more complicated than this. Archaeological results were not particularly relevant to policy-makers and NGOs in their raw state, or even in the form of a written-up scientific article, but the insights gained were of interest. In order to progress from, “Oh, that’s interesting” to the point where the insights can be used, a different way of working is needed. A way that is transdisciplinary and requires the ‘flow of knowledge’ to go in every direction, this may ultimately produce changes in the way we work, the methods we use, and the questions we ask. Enacting this way of working was beyond the limits of the AAREA project, but since the publication of ‘Archaeology has no relevance’ a new project, SOIL-SAFE, has been funded by the Global Challenges Research Fund through the Arts and Humanities Research Council to allow us to develop this idea.

Figure 2 Policy brief image Policy brief exploring the potential role of sediment traps can play in soil conservation practices.

Using one of the original case study areas (Konso, Ethiopia), SOIL-SAFE will build on the relationships created during the AAREA project. It will bring together those working in archaeology, ethnobotany, development studies, NGOs and those who live and work in the landscape to co-create a method with archaeological insights embedded from the beginning. Knowing how an agricultural system was built and operated over time is clearly relevant to an understanding of its current sustainability, but discussions of future sustainability must include everyone that is invested in this future. As archaeologists we can tell people what happened in the past, but the relevance of this information can only be determined through open conservation with the people that may choose to apply it. 


The paper ‘Archaeology has no relevance’ is co-authored by Suzi Richer, formerly with National Trust, and Daryl Stump and Rob Marchant of the University of York.

Upon Closer Inspection…

Author: Joshua Bobbett, National Trust

Looking at analytical techniques and equipment during NHSF and UCM’s workshop ‘What can heritage science do for you?’

I attended the workshop entitled ‘What can heritage science do for you?’ on the 12th March 2019 at the British Library, held as part of British Science Week. Dr. Paola Ricciardi and Dr. Lora Angelova supported by the excellent staff at the British Library’s conservation department were able to provide a whistle-stop tour through the use and benefits of:

  • FTIR
  • Portable XRF
  • IR Imaging
  • Raman Spectroscopy
  • FORS

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Practical applications of analysis equipment along with the pros and cons of certain equipment were explored.

Exciting case studies of current analytical work were presented and used to colour the reasons of how heritage science can complement the usual glamour of engagement at our museum and gallery exhibitions. A personal highlight was discussion on the recent analysis of Isaac Oliver’s cabinet miniature of Lord Herbert of Cherbury (on display at Powis Castle in Mid Wales). Using the equipment listed above, Dr. Ricciardi’s explanation of how analysis brought forward the mystery of how Oliver may have learnt the art of cabinet miniatures in Flanders and not Britain as previously thought, based upon the analysis of green copper sulphate pigments displayed how these machines can offer so much more than just identification and data.

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Interpretations of spectra were shown to give ideas on further application of the equipment for our own collections.

The practical session during the afternoon gave the chance to get hands on with the equipment and get a good idea of the intended use, reliability and cost of each machine. The range of equipment and knowledge available during the day was able to complement all levels of experience, yet highly recommended for those employed in the heritage sector that are curious about covering another aspect of collections care which can often take place under the radar.

It is well worth keeping an eye out for more training and workshops from the NHSF on ICON’s website and if you’re employed in the heritage sector, checking if your own organisation is a member too!

What can Heritage Science do for you? ‘Framing research questions and developing research projects’

Author: Veronica Ford

In this opening section of the workshop Lora and Paola focused on how to clearly and carefully frame research questions and how museum professionals can establish a constructive dialogue with the heritage scientist carrying out the research. The need to set realistic, manageable, and targeted research goals was rightly emphasised, with the course leaders suggesting a frequent pitfall was for researchers to be too ambitious with their aims – for instance requesting all pigments on a painting are analysed as opposed to just one or a select few.

It was shown that it is fundamental that the correct data is gathered in the correct way for a research project to be successful. To determine this it is important to be clear what analysis is being used to inform. The course leaders divided research projects into two principle types: practice based and practice led. Many curatorial questions about an individual object fall under the category of practice based research, such as determining the authorship, provenance, and composition of an object. Practice led research, in this context, can often involve determining the correct conservation technique for a particular object or group of objects.

One of the major strengths of the workshop, and this section in particular, was how the course leaders liberally used case studies to elucidate and contextualise their examples of research questions. This helped to show the potential scope of research projects. For instance, visible light induced luminescence was used to help determine the provenance of a manuscript from Cambridge University which had both Frankish and English elements. Analysis indicated that the blue pigment of the manuscript contained Egyptian blue, a pigment which is found more regularly in English not Frankish manuscripts of this era, thus indicating that the manuscript was likely of English manufacture. This example showed how important research questions can be answered through the careful selection of specific analytical techniques to analyse specific datasets.

Particularly beneficial was how the course leaders, as heritage scientists themselves, acknowledged the unique problems and limitations of working within the heritage sector, such as the need to create representative aged samples to carry out testing. At the root of the course was an awareness that conservators often tread the fine line between the objective and the subjective when making conservation decisions, as well as what this means when interacting with scientists – particularly those that are not heritage scientist specialists – who tend to work well within the realm of the objective.

Veronica Ford ( is an Assistant Preventive Conservator at Bodleian Libraries (@BodCons ). 


Reflections on our ‘What can heritage science do for you?’ workshop

Over the next week, we will be publishing reflections from attendees of our ‘What can heritage science do for you?’ workshop that we held in partnership with the University of Cambridge Museums (UCM) back in March.

The one-day workshop took place at the British Library to explore the benefits of heritage science research in the context of collections-based research and outreach activities.

Participants learnt about a range of analytical methods, which methods can be used to learn more about the materials composition, history, original context and current conservation and storage needs of archaeological, archival and museum objects.

During the workshop, real case studies of heritage science research applied to a range of objects were presented and discussed.

Participants were asked to contribute their experience of, or aspirations for, collaboration with heritage science researchers. The workshop was targeted at conservators, curators, early career scientists, collections managers, archivists and librarians working in museums, archives, libraries and historic houses.

A limited number of free places were available to employees or members of NHSF member organisations.

Keep an eye out for out upcoming posts!

How to Hack Heritage Science!

Authors: Ida Ahmad, Rosie Brigham

The recent Heritage Science Hackathon held at UCL Here East on the 18th and 19th of May was a resounding success, organised by Ida Ahmad, Rosie Brigham and Gavin Leong. It brought many people from different backgrounds to work on issues faced by two local heritage institutions. Originally emerging from the tech sector, hackathons are events, usually lasting the weekend, which gather people from across different sectors to compete in teams to create solutions to common problems, in this case, problems faced by the heritage partners.

After an initial ideas and brainstorming session, participants broke up into teams of up to 7 to work on their solutions. Eastside Community Heritage was looking for an effective and sustainable way to open up the Hidden Histories archive whilst Thames Festival Trust asked contestants how they could better collect, map and archive smells and sent memories to assist in their upcoming program The Barking Stink.

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The event brought in participants from many different professional backgrounds across both the technology and heritage sectors.

hackathon 2
Participants split up into teams to discuss how to solve the problems posed by one of the institutions.

Workshops related to the challenges gave attendees the opportunity to delve deeper into some of the scientific and technical aspects of heritage science. Cecilia Bembibre delivered a fantastic hands on workshop that looked at what heritage smells are, and involved asking the groups to model out of playdough the form of the smell in her specially created ‘smell pens’ were. Giles Bergel delivered a similarly interesting talk that looked at the different ways computer vision is being used across digital archives whilst Rosie Brigham taught an introduction to web development, to give a technical edge to any participants who were looking to upskill.

hackathon 3
Cecilia’s workshop was fantastically received by participants.

At the end of the second day, each team had to pitch the solutions they had been working on to a panel of judges. In total eight pitches were made, Initially, two prizes were up for grabs; one for the best idea relating to each heritage partner. These were awarded to teams SearchOral and KAD. SearchOral created a scalable and searchable database of transcripts, through which researchers could request access to the Hidden Histories archive. KAD created an innovative way to present heritage smells in their local context in East London using totems. The judges were so impressed by the calibre of all the pitches that they decided to award a third prize to team Aurora, for their plan to create a lightweight device that captured the chemistry of a given smell in real time.

An immensely fun weekend was had by all, and we can highly recommend the format of a hackathon to engage new audiences with issues, and to find solutions, in Heritage Science. It has proved a successful way to bring new ideas into organisations and form new partnerships.

hackathon 4
One of the Hackathon organisers Rosie being shown a participants project that uses VR.

Alison Trachet: Guest post on the SEAHA conference, 2017

The National Heritage Science Forum (NHSF) provided bursaries to enable three Early Career Researchers to attend the 3rd International Conference on Science and Engineering in Arts, Heritage and Archaeology. Here Alison Trachet shares her experience of the conference.

Last week I traded the daily showers and cloudy skies of north central Florida for the warm, sunny shores of the south English coast to attend the 3rd International SEAHA Conference held in Brighton. SEAHA, which stands for Science and Engineering in Arts Heritage and Archaeology, is a revolutionary academic program training the next generation of heritage scientists. The very name “heritage science” implies collaboration between conservators, historians, and scientists, and thus the emphasis of this conference was on “interdisciplinarity”.

The two-day event began with several warm welcomes and a charge from SEAHA doctoral student Keats Webb to consider what you wanted from the conference and revisit this question after its end. I simply wanted to meet experts and emerging researchers as well as learn current research trends (and possibly hear about post-doctoral research opportunities), yet I experienced so much more. The first keynote speaker, Dr. Robert van Langh, addressed the economic impact of cultural heritage, something I had never considered. Katy Lithgow at The National Trust queried if heritage science is outgrowing interdisciplinary research and becoming its own field. Other fascinating research topics included occupational health and safety issues from pesticides, mechanical testing and characterization of tapestries and ancient Roman glass, and analyzing the smell of potpourri. I particularly enjoyed the budget air velocity measurer developed by Dr. Josep Grau-Bove: a thin strip of paper calibrated to register certain air velocities.

We ended the first day with a private tour of the Royal Pavilion, King George IV’s ornate seaside home.

Image of Royal Pavilion, Brighton
The Royal Pavilion, a famous Brighton landmark and unofficial mascot of the conference.

Despite being sold by the royal family, used as a hospital in World War I, set afire, and crushed by a heavy stone, the Pavilion can still be visited by the public thanks to heroic restoration efforts from a diverse team, making the building a perfect mascot for the conference. After our tour, I wandered about the Brighton museum with a glass of wine, nibbled on delicious appetisers, and chatted with new acquaintances about our professional backgrounds and interest in heritage science. We had the opportunity to individually talk to research presenters during these social events as well as during coffee breaks, the poster session, and at dinner with new colleagues. 

Image of SEAHA conference poster session
Curious conference goers enjoying the poster session

The SEAHA conference was the perfect place for me to catch up on relevant research, network with experts from a wide variety of fields including conservators, scientists, and industry members, and meet the next generation of heritage scientists. I look forward to next year’s conference, where perhaps I can share my own research struggles and results.

Image of seagull
One attendee was very keen on discussing ginger biscuits during a coffee break


The 3rd International SEAHA Conference was held at the University of Brighton, UK from 19-20 June 2017. The Book of Abstracts is available at:

This is heritage science…medieval window glass

In this post, David Dungworth of Historic England explores new ways of looking at decorated medieval window glass. He explains the use of two X-ray based techniques to improve the visibility of the decoration on the glass, traditional X-radiography and a new technique, scanning micro X-ray fluorescence (µXRF).


Coloured, painted and sometimes stained window glass decoration has been a feature of English churches for over a millennium. The ‘atmosphere’ inside a church often depends on the lighting and the decorated windows give daylight rich and varied hues.

While the earliest decorated windows were simple ‘mosaics’ of coloured glass, most later windows were also painted to illustrate scenes from the bible, the lives of saints, royalty, heraldry or benefactors. Some medieval window glass remains in its original windows but most has been moved at least once and much of it has been destroyed.

Medieval window glass has also been found by archaeologists. Although the decoration on some medieval window glass survives well, the glass itself tends to corrode which can make the glass ‘unreadable’. The decoration on a significant proportion of decorated medieval window glass from archaeological excavations is simply not visible.

Hugh Threlfall recently donated a collection of medieval window glass to Historic England which is being used to test a new approach which should improve the ways in which we can view its decoration. The glass (over 1000 fragments) is generally in rather poor condition. Some examples have corroded so much that they are now opaque and the decoration all but invisible (in some cases a layer of mortar appears to have been applied to the decorated surface of the glass).

Imaging the Decorated Glass

We have explored the use of two x-ray based techniques to improve the visibility of this decoration. Traditional X-radiography works well in some cases and we have also begun to use a new technique – scanning micro X-Ray Fluorescence (µXRF). X-ray fluorescence is widely used to discover the chemical composition of materials, by micro-focussing the X-ray beam it can be directed on a tiny spot (0.02mm). By scanning (using a motorised platform) it is possible to scan across the surface of an object. Importantly the paint has a different composition to the underlying glass: it contains high levels of iron and lead. By looking at scans of these two elements we get a picture of the original decoration.

Types of Decoration on the Glass

So far just over 200 fragments have been scanned using µXRF and it is clear that the painted designs on many are closely related. Most were part of the same decorative scheme and so were probably made at the same time and came from the same building (and possibly even the same window). There are a few fragments which have quite different designs. These designs suggest later manufacture (in most cases these fragments are also far less corroded).

Threlfall Glass #0001. A devil from the Torments of Hell? 

Note the yellow was achieved using silver staining which suggests to us that it was manufactured after the beginning of the 14th century.

Most of the glass is painted to produce simple shapes based on leaves or curvilinear geometric shapes (called grisaille). Commonly, some fields are left plain while others, in contrast, are painted with much thinner lines to produce cross-hatching.

A common border comprises a wavy line and dots but this is clearly related to the cross-hatching as at least one fragment of glass has elements of both. This type of grisaille decoration was popular in the first half of the 13th century. Numerous parallels can be found among glass from York Minster, Salisbury Cathedral and Battle Abbey.




A few fragments of glass are decorated with letters, mostly in a font usually described as Lombardic which was commonly used in decorated glass (and manuscripts) until the later 13th century. Careful examination of the lettering suggests that these were produced by two different glass painters. While TG#0010 is well executed, TG#0019 clearly shows how the letter was produced by scraping away paint (before it was fired). TG#0020 contains the letters REX which possibly refer to a king.

Figurative representations are rare but include part of a seated figure (TG#0022) whose right hand is extended with all four fingers straight (ie not a gesture of benediction) suggesting a secular figure (possibly a king). One fragment (TG#0051) comprises part of a face and another (TG#0109) shows the battlements of a castle from a canopy.

The Ian Threlfall Collection and Alcester Abbey

Hugh’s father (R Ian Threlfall) had been a barrister who, in the middle of the 20th century, helped archaeologically excavate a number of medieval sites (usually with Martyn Jope). Ian found numerous archaeological artefacts when sorting out the family home. He managed to work out where most of them had come from and donate them to the appropriate museum; however, there was a large collection of medieval window glass with no information about its origin. A thorough search through Historic England Archives revealed that R Threlfall was the director of archaeological excavations by the Birmingham Archaeological Society at a Benedictine monastery at Alcester Abbey in 1938. The abbey was founded in the late 1130s but went into decline in the 14th century, had become a cell of Evesham Abbey in 1465 and was dissolved in 1540.

R I threlfall QC
Ian Threlfall

Five minutes with…Keats Webb, PhD student, SEAHA; Digital Imaging Specialist, Smithsonian Museum Conservation Institute

What’s your background in heritage science?

I have been doing scientific and computational imaging for research and conservation documentation of the Smithsonian collections at the Museum Conservation Institute (MCI) for five years. I have a background in fine art photography and was trained on-site by a senior conservator turned imaging specialist in the specific techniques and applications within conservation.

I use a range of techniques including multispectral and hyperspectral imaging, photogrammetry and 3D scanning, digital radiography and reflectance transformation imaging (RTI).

In the autumn, I started a heritage science program for the Science & Engineering Arts Heritage & Archaeology (SEAHA). SEAHA is a Centre for Doctoral Training (CDT) funded by the Engineering & Physical Science Research Council (EPSRC) created by University College London, University of Brighton and University of Oxford.

What’s you role at SEAHA and MCI?

As a student I am researching the spectral and 3D imaging techniques for object documentation and the eventual integration of the techniques.

As a digital imaging specialist, I am working with a range of scientific and computational imaging techniques to answer research and conservation questions about objects and collections coming from conservators, curators and researchers.

Keats Webb 3D scanning a test object (a ceramic figure from Senegal) as part of her research with the Cultural Informatics Research Group at the University of Brighton.


What’s been the most exciting/challenging thing you’ve worked on recently?

Part of my research has involved a case study imaging collection items from the Freud Museum in London, UK. The Museum is Freud’s last residence where he moved in 1938 to flee from the Nazi’s in Austria. After Freud passed away in 1939, his daughter lived in the house for another forty years and the Museum opened in 1986. The collection is a combination of libraries, archives and about 2000 antiquities (Roman, Greek, Egyptian and Oriental). Freud was very interested in archaeology and antiquities and used archaeology as a metaphor for psychoanalysis. It was quite exciting to be working in Freud’s study and to be able to image a wide range of objects of different materials and origins.

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Keats imaging a white ground lekythos (#4492) at the Freud Museum.


Who inspires you?

In 2009, I was taken on as an intern by MCI Senior Furniture Conservator, Melvin Wachowiak. Mel was a Senior Furniture Conservator turned imaging specialist with an enthusiasm and passion for conservation and new technologies. Mel was very generous with sharing his knowledge and expertise and he was dedicated to mentoring and training others. I had the privilege of having Mel as a mentor for nearly five years. He was very thoughtful and meticulous in his work, he valued collaboration, he was enthusiastic about the process and results, and he had a priority for accessible techniques that maintained innovation.  Mel passed away in May 2014, but I still find him to be an inspiration for the work that I do and will continue to do.

What do you love most about your job?

I absolutely love my work as an imaging specialist at MCI!! MCI does not have a collection, but supports the 19 Smithsonian museums and galleries in addition to the research facilities. This allows me to work with a range of collections and materials, which makes the work  interesting and exciting. I have had the opportunity to work on paintings, mummies, musical instruments, fossils, just about anything you can imagine in a museum collection.

As a student, I have had an incredible opportunity to expand my skill set and focus on my research abilities while working on different collections and making new contacts. I enjoy meeting other heritage professionals that are excited and interested about cultural heritage imaging, and the SEAHA program has allowed me to expand my network into the EU.

In a single sentence, tell us what’s great about heritage science?

The interdisciplinary nature of the field and the ability to use science to learn more about our heritage makes heritage science really exciting and great!


Find out more about SEAHA and its work at