Using scientific analysis to investigate the unusual discolouration of a David Livingstone letter

In this week’s blog, find out how conservators from the National Library of Scotland and National Museums Scotland have been using scientific analysis to discover more about a letter by famous explorer David Livingstone…

The National Library of Scotland’s collections include a considerable number of letters by David Livingstone, most of which are written a on a white laid paper with an address embossed on the top right corner of the first folio.  One of these letters is strikingly different from the others in its appearance, and the reasons for this were recently investigated in a collaborative heritage science project between the Library and National Museums Scotland. The project team comprised Lore Troalen and Jim Tate from NMS and Isobel Griffin and Simona Cenci from the National Library of Scotland.

The letter in question (Acc.13333) (Fig.1), dated 16 April 1865, is written on a very brittle paper that shows a dark, uneven colour. Apart from the colour, this paper appears to be the same as the white paper used by Livingstone for the other letters he wrote around this time, with an embossed address in the same place. This suggests that the dark colour may be the result of chemical degradation, rather than the way the paper appeared originally. However, the discoloration is more severe than the yellowing which often occurs as paper ages, for example as a consequence of exposure to light.

Acc.13333 showing the brown colour of the paper

Acc.13333 showing the brown colour of the paper

Scientific analysis was proposed to investigate the nature of the degradation processes that lead to the brown discolouration, which would be of general interest and of practical use in determining whether or not to attempt to remove the discolouration. Additionally, it was hoped that some information about the various coloured inks in the letter might be obtained. The analysis was undertaken non-invasively using X-ray fluorescence (XRF) and Scanning electron microscopy in Backscattered mode/energy dispersive X-ray Spectroscopy (SEM-BSC/EDS), with the SEM in Envac mode.


XRF results

The analysis of the ink with the XRF was problematic, because the beam size (about 2 mm x 1.5 mm) was larger than the ink marks, making it difficult to separate the ink from the paper surrounding it, not to mention the paper underneath the ink. However, the results suggested that all of the inks seemed to be iron based, with traces of copper and zinc, and possibly more zinc in the brown ink.

With regards to the paper itself, the XRF showed significant amounts of sulphur and iron, with the iron present in higher concentrations in the darker areas of the paper. This was interesting because in the previous analysis of various other papers of a similar age, NMS has not detected iron at comparable levels.

SEM/EDS results

The SEM-EDS analysis confirmed the presence of iron in the ink that was tested, as shown in the images below.

The area of ink which was analysed using SEM-EDS

The area of ink which was analysed using SEM-EDS

Image above: A detail of an area of writing; the green colouring shows the presence of iron, corresponding to the places where ink is present, and showing that the greatest concentration is where two strokes of the pen overlap

Sulphur was also present in the ink, as seen in the spectrum below. Other elements present in smaller amounts were calcium, sodium, magnesium, aluminium, silicon, phosphorous and potassium, also with zinc in some samples. All samples showed high levels of carbon and oxygen.

With regards to the paper, the elements detected were iron, sulphur, magnesium, aluminium, silicon and calcium, again with carbon and oxygen.

EDS spectra for an area of ink (red) and an area of paper (yellow). The elements zinc (Zn), potassium (K), sulphur (S) and iron (Fe) are notably higher in the ink.

EDS spectra for an area of ink (red) and an area of paper (yellow). The elements zinc (Zn), potassium (K), sulphur (S) and iron (Fe) are notably higher in the ink.

The SEM images of the surface of the paper at high magnification showed in fascinating detail how the ink cracks as it dries out, forming a surface layer which partially obscures the paper fibres.

SEM-BSC micrograph of a rectangle of the paper measuring about 0.6mm across, showing  a line of ink running up the centre

SEM-BSC micrograph of a rectangle of the paper measuring about 0.6mm across, showing a line of ink running up the centre

The SEM images also show small and generally angular particles present amongst the paper fibres. The fact that these particles show up brightly tells us that they contain elements which are different from the paper fibres.


Discussion and conclusions

Calcium, iron and sulphur are known to be commonly found in iron gall inks, with the concentrations of other elements varying depending on the provenance of the ink[1]. Given that calcium, iron and sulphur as well as zinc were all found in significant quantities in the inks tested, and that the inks are brown in colour, they seem very likely to be iron gall inks.

It is possible that some of the elements found in the paper may be from water soluble components within the inks, dispersed through the paper by wetting, although this seems unlikely to be causing such a general brown colour throughout the paper.

Various reasons for the dark brown colour of the paper were proposed by the project team:

  1. It could be due to darkening with smoke, which seems plausible because sulphur as well as carbon is present;
  2. Since iron is present, it could be due to particles of iron oxide, which were possibly introduced through storage of the letter in a damp and rusty container;
  3. It could be an organic coating such as oil or wax, which would be difficult to detect with XRF or SEM/EDS; such coatings were sometimes applied to make paper more translucent, although a translucent paper would generally have been used for a copy of a letter and this letter seems unlikely to be a copy because it has an embossed address.

If the small, angular particles seen in the SEM images are the substance causing the brown discolouration of the paper, their appearance makes them more likely to be a sooty material or iron oxide than an oil or wax. However, it is also possible that they are a calcium compound introduced during the manufacturing of the paper.

Hence the analysis raised as many questions as it answered, and there were many suggestions for further testing, which could include:

  • Further SEM-EDS analysis, to identify the elements present in the small, angular particles seen in the SEM images;
  • Preparation of replicas to introduce soot and iron oxide, followed by analysis of the replicas and comparison of these results to the results for the original letter;
  • SEM imaging of some of the other letters written by Livingstone at around the same time, followed by morphological analysis of the images to establish whether all of the letters were written on the same type of paper[2];
  • Analysis of the letter to look for organic oils and waxes, for example with Fourier transform infrared spectroscopy. Although it seems unlikely that the paper was coated with oil or wax, it would be helpful to eliminate this as a possibility.

If resources permit, we will tackle some of this analysis in the future, and the mystery of the brown discolouration may be solved. Until then, the letter will remain untreated. And who knows – perhaps it will remain that way forever as a testimony to the letter’s unusual storage history, be that in a smoky room or a rusty old box!

For more interesting conservation conundrums and heritage science research, please follow the National Library of Scotland and National Museums Scotland on Twitter (@NLSColl_Care; @ConserveNMS).

[1]                      García, J.A., Ruvalcaba Sil, J.L. and Meeren, M.V. (2014) ‘XRF Study of Mexican Iron Gall Inks: Historical and Geographical Overview of their Chemistry’, MRS Proceedings, 1618, pp. 31–41. doi: 10.1557/opl.2014.453.

[2]                      Kazuyuki, E., Masato, K., Masuchika, K., Barnard, M., Matsuoka, K. and Whitfield, S. (2007) ‘Analysis of morphology and elements on the paper specimens of the Stein collection of the British Library’, in Tradition and innovation: proceedings of the 6th IDP conservation conference, eds. L. Shitian and A. Morrison, National Library of China, Beijing, China, pp. 37-51.


Meet the Committee – Emily Hick

This week we bring you another edition of our ‘Meet the Committee’ series. Today we talk to Emily Hick, the Digital Content Officer….


Emily working on a book at the Centre for Research Collections, University of Edinburgh

What is your main area of conservation?

Anything to do with paper! I trained in the conservation of fine art at Northumbria University, where I specialised in works of art on paper. I now work at the Centre for Research Collections (CRC), University of Edinburgh mainly with rare books and archives.

What is your position within the Icon Scotland Group?

I am the Digital Content Officer. I organise contributions to the Icon Scotland Group blog, Facebook and Twitter page and the main Icon website. I am passionate about conservation, and welcome any opportunity to promote it! Scotland has a vibrant conservation community, so there is always lots to share and talk about. If you have an event, project or conservation opportunity in Scotland that you would like to me shout about – email me at!

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ISG Committee Away Day

Hazel Neill, the newest member of the Icon Scotland Group Committee, describes the group’s recent away day to Kelvin Hall in this week’s blog post….

A Glasgow institution, Kelvin Hall has been the setting for every conceivable cultural and sporting event since it first opened in 1927. It is entirely fitting therefore [its former purpose having been usurped by new facilities across the city] that it should be re-developed as a repository for collections from the Hunterian Museum at the University of Glasgow, Glasgow Museums and the National Library of Scotland, as well as retaining its services as a sporting centre.

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Paper Conservators in Scotland, News and Ideas Exchange 2017

By popular demand we are holding another ‘5 minute presentation’ event! Read about the previous exchange events here and here.

When: 1.15pm for 1.30pm start, Wednesday 19th April 2017
Where: Centre for Research Collections, 6th Floor, University of Edinburgh Library, 30 George Square, Edinburgh EH8 9LJ
Cost: Free! Refreshments included. Thanks to ICON SG for financial support.

This event is an informal opportunity for us to get together to share news and information about our current work. We are looking for 5 minute presentations where you can talk about a topic that you think paper colleagues would be interested to hear about. We invite paper people in Scotland of all levels of experience to contribute, and are hoping to have a very supportive and non judgemental afternoon. There will be tea and coffee at the start, at the end, and the in the middle, so there will be plenty of opportunity to chat to colleagues.

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Review of the 19th Annual Plenderleith lecture “Antiquities trafficking – 21st century developments”

It was a full house for the Icon Scotland Group’s Annual Plenderleith Lecture last month, this time in Glasgow. The event proved such a draw that some members travelled from as far afield as Bristol to attend, and the Icon Chair of the Board of Trustees, Siobhan Stevenson, had come over from Belfast.

The group gathered at the St Mungo Museum of Religious Art and Life to hear Dr Neil Brodie address a controversial and highly topical subject: the global trafficking of antiquities and other cultural objects.


Plenderleith lecture

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Conservation Opportunities in Scotland

Two great conservation opportunities have become available in Scotland this month.

The first is for a post-doctoral research assistant at Glasgow University (closing date 14 February 2017) and the second is for an 8-week internship at the Centre for Research Collections, University of Edinburgh (closing date 20 February 2017).

Scotland is a great place to live and work, so apply now!


Fireworks over Edinburgh

Conference Review: “Fail to Plan, and Plan to Fail” (Icon Care of Collections Group AGM and Conference)

Interesting review of the Icon Care of Collections AGM and Conference “Fail to Plan, and Plan to Fail” held in October 2016. The event delivered a forward-thinking approach to disaster response including talks on having an emergency plan on a smart phone and the Museum of London’s emergency planning e-learning tool. Read now and reassess your own disaster plan!

The Book & Paper Gathering

The dreaded call from a colleague with a collections emergency is one that no conservator wants to receive; but it has happened to many of us. Small-scale incidents are more common than major emergencies, but planning for an emergency situation of any scale involves a great deal of work to ensure a plan is in place, the right equipment is available and the response will be effective. This year marks the 50th anniversary of the Florence floods; and with more recent disasters like the fires at Clandon Park and Glasgow School of Art on our minds, emergency preparedness seems more necessary than ever.

On 3rd October 2016, Icon’s Care of Collections Group (CCG) held a conference ominously titled “Fail to Plan, and Plan to Fail”, followed by their AGM. The event was held at the British Library and included a tour of the book stacks and salvage equipment…

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Crowdsourcing Conservation

During the Festival of Creative Learning (20-24 February 2017), the Centre for Research Collections (CRC), University of Edinburgh, will be hosting its first ever conservation crowdsourcing event!

Over a two-day period (20-21 February), with the help of 30 participants, they aim to rehouse section II of the Laing manuscripts – the University’s most important written collection.

Folder from section II of the Laing manuscripts

Folder from section II of the Laing manuscripts

Laing’s collection of charters and other papers is of national importance and the most distinguished of its kind in any Scottish university. It is an essential resource for the 18th century, however, it is in poor condition due to its current housing in unsuitable upright boxes and folders. It is an extremely popular collection, but it is difficult to access and there is a risk of further damage every time it is handled.

Section II of the Laing Manuscripts in unsuitable upright boxes

Section II of the Laing Manuscripts in unsuitable upright boxes

Section II of the Laing manuscripts stored in upright box (left) and damage caused to collection due to storage (right)

Section II of the Laing manuscripts stored in upright box (left) and damage caused to collection due to storage (right)

To solve this problem, we want to rehouse the collection in acid-free folders and boxes. During the event, we aim to complete repackaging work of all 137 boxes. Each day will consist of a training session in the morning, followed by practical work. In the afternoon, volunteers will be joined by staff members from the CRC who will talk to them about their roles, whilst helping to carry out the conservation work. Good quality complimentary refreshments and catering will be provided throughout the day to encourage networking during break times. A behind-the-scenes tour of the CRC, where the participants will get to see the newly rehoused collection will be offered after the event.

Places are limited to 15 participants per day. If you are a student or staff member of the University of Edinburgh, you can book on the Monday session, by clicking here and the Tuesday session, by clicking here. If you are not a part of the University, please email to book your place.

Emily Hick

Special Collections Conservator

Conservation in Scotland and Brexit

The Icon Scotland Group were asked for details on what leaving the EU might mean for conservators.  Rather than shrug and say ‘No Idea’, we thought it best to see if we could find some specifics to comment on. Carol, Ylva and Rob put together the below response with help from Alison and Siobhan at London HQ. Our response goes to Built Environment Forum for Scotland (Icon is a member of this) who collate it with others and send to the Scottish Government. Please do let us know your thoughts on this!

Institute of Conservation response to the Built Environment Forum Scotland (BEFS) information request

Icon is delighted to be able to respond to the call from BEFS to inform a response to the Europe and External Relations Committee’s call for evidence on Scotland’s relationship with the EU. We provide information below on the connections, initiatives and relationships that Icon and our profession have with Europe currently.

The Institute of Conservation (Icon) is a registered charity and the professional body for the conservation of cultural heritage. Icon raises awareness of the cultural, social and economic value of caring for heritage and champions high standards of conservation. Icon Scotland Group is one of Icon’s 16 special interest groups.

Heritage Science research funding

The science of heritage conservation is a relatively new field and is a field where the UK has a global standing and reputation. This research is essential to inform the care and preservation of our cultural heritage. Around 50% of funding for heritage science comes from the EU. This compares to about 7% of total public research funding being from the UK. (Source: conference on Science and Engineering in Arts, Heritage and Archaeology (, Dr Adam Cooper, Lecturer in Social Science and Public Policy at UCL)

Ongoing research is needed to develop improved ways of looking after our historic buildings and museum collections that are continually in need of conservation and maintenance.

If EU funding for this research is removed without replacing it we will lose the ability to care for much that is of value to us as a country and much that is the primary reason for overseas visitors to come to the UK.

Skills Training and Provision across the UK and EU

There are a little over 3000 conservators working in the UK.2 This small field relies on cross-border training and the movement of specialists between nation states. For example, a book conservator may train in Germany and practice in Scotland or a textile conservator may train in Scotland and practice in France.

The sector is too small for the UK to provide education and training in all specialisms at all levels within its borders. We need, for example, the ability to import stone conservators from Germany who get a level of training that is simply not available in the UK.

The profession of Conservator is included in the EU Free Movement of Regulated Professionals legislation which formalises the ability of UK trained conservators to use their qualifications across the EU and vice-versa. This free movement of expertise also gives us the opportunity to take skills acquired in the UK and use them overseas. For example, stained glass conservators could provide expertise to projects in Ireland.

The training of conservators that is available in Scotland (primarily the Textile Conservation Centre at Glasgow University) relies on having non-UK students. This specialist post-graduate training will be less attractive to potential students if these students become unable to use their training in the rest of the EU (if they are UK citizens) or in the UK (if they are EU citizens). It will also be less attractive to EU students if they are required to pay non-EU tuition fees (currently about double EU fees). This would result in less demand for the courses and might risk their viability. This in turn risks further undermining training provision for the UK and the EU.

We hope this is useful to the Forum, and look forward to hearing about progress in due course.

Dismantle, Conservation and Installation of William Chambers Statue, Edinburgh

This month’s blog post comes from  Jonathan Leburn, a Sculpture Conservator with Graciela Ainsworth Sculpture Conservation Ltd. He describes the recent treatment of a monumental statue in Edinburgh….

Moving sculptures is a large part the conservation work that we do, some sculptures however are larger than others.

Front and back of statue

Front and back of statue

We have recently finished the conservation of a 3 metre tall and over two ton in weight, bronze statue of William Chambers and 5 associated bronze plaques, as part of the revamp to create more public space outside the National Museum of Scotland.

The statue and plinth which date from 1891 have only been moved about 10 metres from their original position, however in order for the conservation works to be undertaken the sculpture and plaques needed to travel a little further.

The fixing methods of sculptures to their plinths is always somewhat of an unknown, and can often make removal of objects tricky. We will always try to remove the sculptures causing as little damage as possible to the original piece.

On this particular occasion it was clear that there were a number of doweled anchor points set into the stone from three footplates. These clearly couldn’t be removed without causing significant damage to the stonework, and as a result the next best option was to cut through the bronze footplates.

Before this could be done the sculpture was carefully slung and a hi-ab crane was brought in to take some of the sculptures weight and ensure that when the last of the fixings had been cut the sculpture would be secure and would not topple.

Cutting through the bronze footplates to free the sculpture

Cutting through the bronze footplates to free the sculpture

The sculpture was then carefully raised up off its plinth and over the scaffold, before being lowered onto the back of the hi-ab lorry.

The sculpture is lowered onto a large pallet with thick plastazote softening

The sculpture is lowered onto a large pallet with thick plastazote softening

Once back at our workshop the sculpture was initially placed in the workshop on his back. This allowed us to have a good look at the internals of the sculpture and with the aid of an endoscope we could view the condition of the bronze right the way up the sculpture. Structurally there did not appear to be any significant issues however it is often interesting to see what has been placed up the sculptures, in this case large amounts of twisted ferrous metal bars and stakes.

Ferrous metal found inside the sculpture

Ferrous metal found inside the sculpture

We removed the original fixings and the remainder of the footplates we had cut away from the top stone of the plinth by way of a core drill and then using a hammer and chisel to carefully shock off the remaining concrete attached to the dowels. Once removed it was clear to see the high workmanship of the original fixings that remarkably after all this time were still easily unscrewed from the footplates.

Original fixings having been removed from the top plinth stone

Original fixings having been removed from the top plinth stone

The cut away sections of the footplates were then welded back to their original positions and a new bronze pad was also welded to the underside of each of these footplates to give added strength. Threaded holes were drilled and cut into the new footplate sections to line up with the original holes and new stainless steel dowel was cut to fit into each of the footplates.

The depth of footprint was then increased on the plinth top by way of hammer and chisel to allow for the new bronze footplate sections that had been added. This ensured the sculpture would sit at the same height on the top stone.

Discreet pigmented wax tests were also undertaken at this time on the underside of the left foot to help us decide on the best colour option.


Carrying out wax tests

The sculpture was raised back to its vertical position by way of a tall gantry within the workshop and was then given a thorough washing down with potable water and nylon brushes. This was done to remove general dirt and bird guano present on the bronze surface.

Following this the bronze surface was again brushed, this time using copper brushes to enable removal of loose verdigris and sulphation crust from the surface of the bronze. Small areas of graffiti were also removed at this point using a combination of chemicals.

The bronze was treated with a chelating agent to inhibit against future corrosion to the surface. Following this it was gently heated with a propane torch to remove all moisture.

Considering its age the bronze was in a generally sound state, however there were areas that required attention. Specifically the top of the head was in a poor condition. Being that the head is the most likely spot for a bird to land and with the acidic nature of bird guano it is not uncommon to find that the tops of sculptures are generally in a poorer condition than the rest.

There was quite significant pitting to the head of Chambers that required filling with an epoxy resin. This was pigmented to match the colour of the surrounding bronze.

Top of head prior to filling

Top of head prior to filling

Filling the pitted surface with pigmented epoxy resin

Filling the pitted surface with pigmented epoxy resin

Once all holes had been filled the bronze was again heated, this time to melt the first coat of pigmented wax into the metal surface. Following this first application the sculpture was left to cool down and allow the wax to harden. The wax was then buffed into the bronze to harden it further. A second application of wax was applied to the sculpture cold which again was buffed to harden. This process was repeated twice further in order to increase the layers of protection the wax gives the sculpture. It also increases the depth of colour to the sculpture as the pigmented wax layers build up.

Applying first coat of wax

Applying first coat of wax

Following completion of the conservation works the sculpture was transported back to the new site of the original plinth which itself had been dismantled, conserved and re-built.
To ensure the sculpture would be completely solid on top of its plinth a core drill was used to deepen each of the original holes that would receive the sculptures dowels. The holes were thus drilled down into the second stone from the top.
The sculpture was then lifted just above the plinth top so the dowels could be screwed up into the footplates. A dry run was then undertaken to ensure that all dowels and footplates fitted correctly into position. Following the successful dry run the sculpture was lifted back up and the holes in the top stone were filled with an epoxy grout. The sculpture was then lowered down into its final position.

Dowels being threaded into position prior to final positioning of sculpture

Dowels being threaded into position prior to final positioning of sculpture

Final positioning of sculpture and plaques

Final positioning of sculpture and plaques

Written by Jonathan Leburn Sculpture Conservator with Graciela Ainsworth Sculpture Conservation Ltd, Edinburgh.