A Colour A Day is a year-long project by Jo Volley, which began on the first World Pigment Day, 22 March 2020,  to celebrate one colour each day by recording a swatch. This is the post of colours created for Week 2; 30^th March – 5^th April.

This week’s contributions are group of colours made from natural sources that Jo has collected and prepared as pigments.

1. Iron Gall Ink
2. Hampstead Heath Ochre no.6
3. Pomegranate Ink
4. Hampstead Heath Ochre no.3
5. Cork Black
6. Prespes Red Ochre
7. Bone Black

It is fair to say that ochres and their origins are poorly discussed in the academic geological literature. Though ubiquitous in the landscape, they are largely ignored by most geologists. They occasionally pique the interest of economic geologists but are generally dismissed and shovelled away in favour of something more shiny. Ochres can form in a wide range of geological environments on Earth and indeed, on Mars (there’s a reason it’s red), but in this post I’m going to focus on ochre forming on the weathered surfaces of solidified basalt lava flows (I may get around to writing about other ochre-forming environments in the future). At its simplest, ochre is defined as an earthy deposit predominantly composed of metal-rich oxides or oxide-hydroxides. By far and away, iron ochres are the commonest, but ochres of other metallic elements such as cobalt, nickel, copper etc. can also form. Ochres form in the surface or near-surface environment, in the presence of oxygen and water. Iron ochre formation is accelerated by warmer Mediterranean or tropical climates, and the presence of red rocks is therefore often indicative of past warm climates in the rock record.

The inspiration for this post was a photo (above) posted on Instagram for World Pigment Day by Scott Sutton of an ochre layer between basalt lava flows in the Rio Grande Gorge of New Mexico. This region’s geology is dominated by basaltic volcanism which erupted in the upper Miocene, around 10 million years ago. These eruptions were not like any basaltic volcanism we can observe from active volcanoes anywhere on Earth today. They were large-scale, effusive flows which spread out covering large areas and forming a plateau composed of a thick pile of solidified lava. Such formations are subsequently known as plateau basalts or (continental) flood basalts. The basalts of the Rio Grande Gorge are part of the Taos Plateau Volcanic Field (TPVF). Following the end of volcanism, the Rio Grande cut down through the basalt pile exposing 180 m of section. Scott’s visit into the river gorge and his photograph revealed part of this geological history. The old adage says that if you want to hunt elephants, first you must go to elephant country. The same is true for geological prospecting; horizons forming between successive basalt lave flows are typically ochre-rich, and therefore these are good places to go pigment hunting. Certain types of rocks form in certain regions, and their occurrence is generally controlled, ultimately, by the regional plate tectonic environment. The kind of basalts that are erupted into rift valleys – areas of continental extension, which is the setting of the Rio Grande – are typically iron-rich. Most basalts contain significant iron, but continental flood basalts are the richest. When they cool and become weathered, ideally in a warm, wet climate, they produce iron-rich soils; ochres. These ochres are then sealed and preserved by the next lava flow that covers them. Later in their geological history, these so-called interbasaltic beds can be further weathered and the ochre more concentrated by groundwaters which percolate through these porous layers. Layers of basalt are impervious.

This series of geological logs, from a guide to the Rio Grande basalts by Dungan et al. (1984), shows how the individual basalt flows (white) are interlayered with sediments, including ochre palaeosols (stippled). Like so many other papers on this subject, the authors record much about the basalts and little, if anything is said about the ochres.

In the British Isles the British Tertiary Volcanic Province (BTVP) is a series of flood basalts formed as the North Atlantic Ocean opened around 60 million years ago. Most famously, these are exposed in Northern Ireland on the Antrim Coast where they form the Giant’s Causeway. This basalt pile is famous for its ochreous interbasaltic horizons and is the one place where a series of papers have been published on ochre formation. Although several ochre-rich interbasaltic horizons occur between the flows of the Antrim plateau basalts, there is one 30 m thick horizon of weathered basalt and associated palaeosols which has attracted attention for many years. It is known as the Inter-Basaltic Formation (IBF) and the ochres, known locally as boles (a good painter’s term) are mostly laterites, that is aluminium and iron-rich ochres (aluminium-rich ochres are known as bauxites), The main aluminium mineral present is gibbsite. Laterites are typically orange in colour. Yellow goethite and red hematite iron ochres also occur here, along with purple-coloured ‘lithomarge’ which is rich in clay minerals and hematite.

The Antrim Basalts from an early publication by Cole et al. (1912). The huge Bole Bed is inexpertly marked out in (appropriately) red paint.

The analyses carried out on the Antrim ochres suggests they formed in warm, wet and occasionally hot, arid climates in the early Palaeogene. Similar horizons are also found in India’s Deccan Traps flood basalts.

A figure from Ghosh et al. (2006)’s paper on the boles of the Deccan Traps; interbasaltic ochre beds formed here in very similar climatic conditions to those of the Antrim Basalts. This 2 km thick pile of basalt flows was erupted towards the end of the Cretaceous, 66 million years ago. 

Basalts are composed of three main minerals, olivine, pyroxene and plagioclase feldspar. The iron minerals are produced from the breakdown of olivine and pyroxenes, whereas the aluminium-rich laterites and bauxites form due to the breakdown of the feldspars.  Hematite (iron oxide) and goethite (iron oxide hydroxide) are the main and most stable iron ochre constituent minerals. Gibbsite (aluminium hydroxide) is the predominant mineral in laterites and bauxites.

You don’t need huge plateau basalts to find ochreous interbasaltic beds. You can find them on most volcanoes that have erupted basalt. These examples below are in the lower eruptive sequences of the Greek volcanic Island of Thira (Santorini). The reddened layers are clearly seen between the layers of grey-black basalt.

A view towards Firostefani on the Santorini Archipelago. You can see the reddened ochre layers between the grey coloured basalts.

Follow Scott Sutton on Instagram, and visit his webpage here.

Download this article as a pdf document

 

References and further reading

Cole, G. A. J., Wilkinson, S. B., McHenry, A, Kilroe, J. R., Seymour, H. J., Moss, C. E. & Haigh, W. D., 1912, The interbasaltic rocks (iron ores and bauxites) of North East Ireland., Memoirs of the Geological Survey of Ireland., Dublin, Ireland, 143 pp.

Dungan, M. A., Muehlberger, W. R., Leininger, L.,  Peterson, C., McMilan, N. J., Gunn, G.,  Lindstrom, M. & Haskin, L., 1984, Volcanic and sedimentary stratigraphy of the Rio Grande gorge and the late Cenozoic geologic evolution of the southern San Luis Valley., in: Rio Grande Rift (Northern New Mexico), Baldridge, W. S.; Dickerson, P. W.; Riecker, R. E.; Zidek, J.; [eds.], New Mexico Geological Society 35th Annual Fall Field Conference Guidebook, 157-170

Ghosh, P., Sayeed, M. R. G., Islam, R. & Hundekari, S. M., 2006, Inter-basaltic clay (bole bed) horizons from Deccan traps of India: Implications for palaeo-weathering and palaeo-climate during Deccan volcanism., Palaeogeography, Palaeoclimatology, Palaeoecology 242, 90–109.

Hill, I. G., Worden, R. H. & Meighan, L G. 2001, Formation of inter basaltic laterite horizons in NE Ireland by early Tertiary weathering processes. Proceedings of the Geologists’ Association, 112, 339-348.

Ruffell, A., 2016, Do spectral gamma ray data really reflect humid–arid palaeoclimates? A test from Palaeogene Interbasaltic weathered horizons at the Giant’s Causeway, N. Ireland., Proceedings of the Geologists’ Association., 127, 18-28.

A Colour A Day is a year-long project to celebrate one colour each day by recording a swatch of it.

International Colour Day and World Pigment Day fall respectively on the 21^st and 22^nd of March. The project started on 23rd March which was coincidentally also the day lockdown began in the UK.

It has begun with the Liquitex Heavy Body Cadmium Free range of 7 colours, as seen here,  and tomorrow will progress onto a range of natural colours.

Jo Volley, 30 March 2020

Day 1. Yellow Light

Day 2. Yellow Medium

Day 3. Yellow Deep

Day 4. Orange

Day 5. Red Light

Day 6. Red Medium

Day 7. Red Deep

Graphite is a naturally occurring mineral pigment, a form of  carbon, which occurs in geological environments which have undergone high temperature metamorphism or where there has been precipitation of elemental carbon from fluids. Vein carbon deposits are regarded as exceptionally pure. Graphite has been used as the main pigment for pencils. A lode of graphite was discovered in Seathwaite in the English Lake District in the 16th Century, when it was assumed to be lead (plumbago) because of it’s sub-metallic, silver grey lustre. Graphite has a very high specific heat capacity (as opposed to the metal lead), so it was initially used for moulds for casting cannon balls. The graphite pencil was exclusively manufactured in Britain because of the particular quality of the Seathwaite deposits, but they were relatively rare. The uniqueness of the Seathwaite deposit was that it could be sawn into square-section rods which could be used for drawing. Most artists and draughtsmen were using silverpoint for drawing at the time and this continued to be used until the mid 19th Century when the ruction of graphite pencils became universal.

For World Pigment Day, artist Sarah Needham wrote about a graphite pigment made from graphite rods used in the steel-making industry.

“I’m really interested in the way that pigments leave traces of our history and human interconnectedness across time and geography. The pigment in these videos is graphite, recovered from graphite rods my Uncle bought at auction when the steel works in a North Yorkshire town were closed down. This is a particular incidence of history that is close to my very own personal history, firstly because my uncle found them, and secondly because on the other side of the family there is a history of stainless steel cutlery making. The industrial graphite took some pounding to get into powder form and I did this by covering it in a cloth before pounding it.

More often I look for pigments that play a role in historical events which have resonance with current events. For example my recent collection From Alchemy to Chemistry uses pigments that were synthesised as a result of chemical analysis, to replace older natural pigments, in the industrial revolution. The connection being an era when technological change revolutionised our ways of being, living, doing and seeing…just like the technological revolutions of
today.”

What exactly are graphite rods? They are used in the steel industry for a stainless steel making technique called the electric arc furnace (EAF) process and for refining the final product (turning steel into stainless steel) in blast furnace processes. The latter were those most probably used by Sarah’s ancestors. Graphite rods are used as electrodes as they can carry huge amounts of electric current. They are made by mixing graphite and pitch and then placing this mixture into tubular moulds. These are then heated so that the pitch turns to coke, this mixture is then heated to extremely high temperatures, in modern process, these are typically 3,000 °C, so that the entire mix of hydrocarbons is reduced to pure graphite.

Follow Sarah Needham on Instagram.

This beautiful colour wheel was created for Work Pigment Day by Margot Guerrera, and artist from Santa Fe in the South-West USA and the pigments she has used here have been inspired by the desert landscape in which she lives. Starting at the top, the pigments used are Heart Wuda (heartwood), Campeche Wood, New Mexican Ochre, Copper Vitriol, Azurite and Mixtec Indigo. They represent a mixture of plant-based dyes, geological deposits and synthetic materials, reflecting the world of pigments.

Follow Margot in Instagram and see more of her work here.

Yesterday (22 March 2020) we launched the inaugural World Pigment Day. There was an huge amount of engagement on social media and particularly on Instagram. Over the next few days I will be sharing images and pigment stories from people who posted to celebrate World Pigment Day. First up is artist Polly Bennett, a resident of St Ives in Cornwall, who contributed a series of posts on the colours of the Rainbow. Over to Polly …

Red: Cinnabar Cinnabar is a toxic mercury sulfide mineral that has been used as a pigment for thousands of years due to its bright red colour. It is a pigment in its own right, however, it was also used to make the red pigments known as “vermilion” and “Chinese red”. Cinnabar is a hydrothermal mineral that is usually found in rocks surrounding recent volcanic activity but can also form near hot springs and fumaroles (an opening in or near a volcano). Because of cinnabar’s toxicity, it is a lot less commonly used nowadays.

Orange: Ochre Ochre is a family of earth pigments that includes yellow ochre, red ochre, purple ochre, sienna, and umber. It consists of varying amounts of iron oxide, clay and sand, and ranges in colour from yellow to deep orange or brown with an array of shades inbetween. I have found huge amounts of ochre earth in St Ives, where I am currently staying, and have been slowly but surely grinding and separating the ochre into different shades. The mineral goethite, an iron oxide hydroxide and the main constituent of most yellow ochres, is named after Johann Wolfgang von Goethe, the colour scientist whose death marks the date of World Pigment Day

Yellow: Sulphur Although Sulphur is not a pigment, I found some in a curio shop and was curious to see if it ground into a powder; would it work in the same way?  So I intend to turn it into watercolour and test it out. Historically it has been used to bleach cloth, so it might do something similar when applied over the top of other watercolours. Sulphur occurs naturally as the element, often in volcanic areas, and as the extraction of pigments is very alchemical, I thought it was interesting to note that for centuries, along with mercury and salt, it was believed to be a component of all metals and formed the basis of alchemy, whereby one metal could be transmuted into another.

Green: Green Earth from St Ives Yesterday I was super excited to find a little green sparkly rock on the eroded foreshore. I set about grinding it down and managed to get two shades of green from it, the darker one I immediately made into watercolour.

 

 

Blue: Azurite Azurite is a soft copper mineral, named for its beautiful “azure blue” colour. It has been ground and used as a pigment in blue paint as early as ancient Egypt, and through time, its become much more common. During the Middle Ages and Renaissance, it was the most important blue pigment used in Europe, and through the early 19th century, it was also known as chessylite, after the type locality at Chessy-les-Mines near Lyon, France, where much of the pigment was mined. Here I have mullered the Azurite into glaze.

Indigo: Mussel Shell Blue from St Ives Since landing in St Ives I have been going down to the foreshore every morning to collect mussel shells as I wanted to create a blue pigment to represent the sea, however after being ground the mussels create a light indigo colour that I love! Historically painters used shells as paint pans, so I thought it very appropriate to make watercolour paint with the mussel pigment and use one of the mussel shells as the pan for the paint.

Violet: Cochineal Cochineal is a bright scarlet insect lake pigment that has been used for centuries to dye textiles, drugs, food and cosmetics. A lake pigment is a pigment made by precipitating a dye with a mordant. Unlike mineral pigments, lake pigments are organic.Cochineal is the result of harvesting the female cochineal parasitic insect that live on the cacti native to Mexico, Central and South America. Using soda ash and alum, I extracted the pigment from the insects and added honey and gum arabic to make watercolour.

Follow Polly on Instagram.

 

Today should have been the last day of our Colour and Poetry Symposium at the Slade School of Fine Art. However, like everything else, we have had to postpone this event because of the current pandemic. Jo Volley and I were going to announce at the symposium that we were going to nominate tomorrow, 22 March, as World Pigment Day – basically because we can! We still hope to celebrate this event even though most of us are in isolation or quarantine, I would like to share this with all of you and ask for your support. This initiative is not for profit and is all about collaboration and sharing between all the disciplines that use pigments and mostly just for fun!

We have chosen this date, because it marks the death of the poet Johann Wolfgang von Goethe (28/08/1749-22/03/1832). Goethe was a polymath. In addition to his plays, poetry and prose, he wrote on botany, and importantly published his Theory of Colours in 1810 and went on to publish a series of influential monographs on the understanding of colour. The mineral goethite, an iron oxide hydroxide and the main constituent of (most!) yellow ochres is named after Goethe.

We will be celebrating this tomorrow with a live stream from 12 noon on Longplayer. Please find the link here to listen in.

#worldpigmentday

 

Professor David Dobson was UCL Slade School Scientist in Residence for 2017-2018. Intrigued my the media coverage that the development of the new YIn Mn Blue pigment made in 2017, David was moved to make his own blue and think more about blue minerals in the Earth. David has recently been interviewed in Science Magazine by Kai Kupferschmidt.

David writes …

We live on the blue planet. Blue is so common in our everyday experience that we don’t even notice it. The sky is blue due to light scattering and water absorbs short wavelengths of the visible spectrum making it a pale blue.  But blue minerals are rare; so much so that in medieval and renaissance time blue pigments were reserved for God and the saints.  Most mineral colouration comes from small amounts of transition metal impurities in the mineral structure.  This class of element can exist in several different electrical charge states and the hopping of electrons from one transition metal ion to another causes absorption of light in the visible spectrum and hence colour.

Iron, with allowed charges of 2+ or 3+, is the most common transition metal and so most minerals display the colours associated with electron hopping between 2+ and 3+ iron – red or brown when 3+ dominates and green when 2+ dominates. But deep in the Earth’s interior, at pressures of 180 to 230 thousand atmospheres the most common mineral, ringwoodite, is a rich royal blue. Once again, water is responsible, at least in part. In this case water is incorporated into ringwoodite as protons (H⁺ ions) and it substitutes for the main cations, Mg²⁺ or Si⁴⁺. In order for a stable substitution in a crystal lattice the charges must balance – you can’t replace one silicon (Si⁴⁺) ion for just one proton because the crystal would be left with an excess negative charge which would blow it apart.  Instead the proton is accompanied by an iron ion to make a [Fe³⁺H⁺] substitution on the silicon site.  This pushes the iron into a much smaller site than it usually occupies, surrounded by only 4 oxygen (O^2-) ions rather than the usual 6 oxygens.  This in turn changes the energy of charge transfer electron hopping transitions between iron 2+ and 3+ ions, making ringwoodite blue rather than brown. This [Fe³⁺H⁺] substitution is such a good fit in the silicon site that, if all the ringwoodite in the Earth had as much water as possible in its structure (and that is a BIG if), there could be as much as 4 time the entire volume of the oceans locked up as structurally bound water in the Earth’s mantle and Earth’s interior would be as blue as its exterior.

Here in UCL Earth Sciences we are attempting to develop synthetic structures which mimic the unusual ferric iron structure of ringwoodite but which are stable at atmospheric pressure.  So far we have shown that we can make blue pigments from iron-bearing oxides and are now investigating how much Fe³⁺ the structures can take before they become unstable.  That will determine just how blue we can make them. The prospects are bright…blue.

Ringwoodite synthesised at 20 GPa and containing 10% iron

 

David’s new blue, with about 0.3% iron

 

Three blues created by Fe2+-Fe3+ charge transfer: vivianite (in the centrifuge vial), (on the left) my Fe-bearing zinc germanate with Fe from 0 to 0.3% and (on the right) a Fe-dopes zinc silicate.

 

A a cross- and interdisciplinary event at the UCL Slade School of Fine Art to celebrate International Colour Day and World Poetry Day took place on 20th and 21st March 2019. This included all things colourful and poetic and often both, from talks, poetry readings, to making and mixing pigments, and looking at images in the accompanying exhibition The Nomenclature of Colours.

The symposium was conceived and organised by Jo Volley of the Slade School and the exhibition The Nomenclature of Colours was curated by Jo and Stephanie Nebbia. The photos used here were taken by Gabriela Giroletti and Ruth Siddall.

The full programme is available here.

 

Speakers talking about colour and research were; Michael Berkowitz, Malina Busch, Jane Bustin, Mark Cann, David Dobson, Taylor Enoch, Roland-Francois Lack, Liz Lawes, Andy Leak, Antoni Malinowski, Onya McCausland, Dimitris Mylonas, Ruth Siddall, Henrietta Simson, Estelle Thompson and Edward Winters.

The poets who read from their work were Mataio Austin Dean, Rhun Jones, Sharon Morris, Fabian Peake and George Szirtes. Caroline de Lannoy‘s ‘Colour Tale’ was performed by Caroline and Slade School students, the ‘Colour Tale Choristers’.

David Dobson, Ian Rowlands and Jo Volley demonstrated making and mixing pigments.

Looking at Josef Albers’s silk screen prints from the Slade’s edition of Interaction of Colour in a talk and discussion led by Malina Busch.

An exhibition of pigments in the Material Museum curated by Jo Volley.

RED

This exhibition, installed for the month of November 2018, in the vitrine Material Museum/Museum Material in the foyer of the UCL Slade School of Fine Art, is one of the research outcomes of a project completed during Summer 2018 by UCL students Alexa Marroquin and Jessica Manuel, supervised by Ruth Siddall. Jessica and Alexa are both successful recipients of UCL Laidlaw Scholarships, which gives them the opportunity to undertake academic research in their first year of undergraduate study. Their project, ‘Red Pigments in Roman Britain’ has looked at the range of red pigments available to Romano-British artists and together they have made a comparative study of the ancient pigments available and their modern analogues; rose madder, red lead, cinnabar/vermillion and red ochre. Alexa is studying for an MSci Chemistry and Jessica is studying for a BA History of Art with Material Studies at UCL. Together they have performed scientific analyses of the pigments and also prepared pigments as paints to test their workability and colour.

Jessica Manuel (left) and Alexa Marroquin (right) and their exhibition in the Material Museum.

The Exhibition RED in the Material Museum, UCL Slade School of Fine Art

Over to Jess and Alexa …

‘Within this exhibition, RED, we have decided to include various objects that encapsulate and refer back to our Laidlaw Programme summer research project, Red Pigments in Roman Britain.Coming from a background of Art History with Material Studies and Chemistry, we have used both our interests and practical disciplines within our research to analyse the red pigments used in Romano-British wall painting fragments.

Our research started within familiarising ourselves with articles and texts that broadened our understanding of common red pigments utilised by Roman artists, most of which were taken from archaeological sites or museums and are painted objects from across Roman Britain, and also throughout the extent of the Roman Empire.

From this literature research we determined which of the analytical methods would be the most feasible and efficient to identify organic and inorganic red pigment samples such as: Red Ochres, Red Lead and Cinnabar, as well as the organic pigment: Rose Madder. Of the analytical techniques used across many other studies, we limited our research to UV-VIS, ATR-FTIR, RAMAN, XRD and Polarised Light Microscopy (PLM). We found that the most useful analytical technique was Polarised Light Microscopy, and this by far produced the most fascinating results.

By using all of these analytical techniques we were able to produce a reference data set that we can compare with the pigments found on actual wall painting-fragments acquired from an archaeological site; a Romano-British Villa at Sudbrooke in Lincolnshire. Roman wall-painting fragments were not simply painted in red, but often in bands of different coloured paint that we additionally identified as carbon black and chalk/calcite.’

Installing the Exhibition

 

Key to Objects in the Exhibition

1. Jar containing Mercury(II) Sulfide (HgS) / Cinnabar. This pigment, derived from the natural mineral cinnabar was considered a very valuable commodity in the Roman World. It came from the mercury mines at Almaden in Spain.

 

2. Jar containing Lead(IV) Oxide (Pb3O4) / Red Lead pigment. Often referred to as minium secondarium during the Roman Empire as it was considered as a second-rate pigment compared to its more expensive counterpart, cinnabar. A synthetic pigment, Red Lead was made from scrap lead exposed to vinegar fumes. This produced white lead which could then be roasted to produce this read pigment.

 

3. Jar containing Iron(II) Oxide (Fe₂O₃) / Red Ochre. The main component of red ochre is the mineral hematite, but as this is an impure, geological deposit, other impurities may also be present. The pigment in the exhibition is supplied by Rublev Colours. However ochres are ubiquitous geological deposits and they were a cheap and readily available artists’ material.

 

4. Jar containing Rose Madder pigment. Madder is a dye derived from the plant species Rubia peregrina or R. tinctorum. Rose Madder produces a bright-pink pigment. This pigment is supplied by Cornelissens.

 

5. Large wall-painting fragment from the Romano-British Villa at Sudbrook, Lincolnshire. Five different coloured bands are present. The red band was analysed by Raman spectroscopy, and hematite was identified as the main pigment used.

6. Small wall-painting fragment from the Romano-British Villa at Sudbrook. The bright-red band was analysed, by Raman spectroscopy, and cinnabar was identified as the pigment.

 

7. Image of Hematite crystals in Red Ochre under Plane Polarised Light. In this sample hematite crystals are finely grounded and have a deep brown-red body colour. This sample also contains crystals of yellow ochre, goethite. x 400 magnification, plane-polarised light.

 

8. Image of Red Lead crystals viewed using polarising light microscopy under crossed polars. Some particles exhibit emerald-green interference colour characteristic of red lead. x 400 magnification, cross-polarised light.

 

9. Mineral Sample of red ochre from Clearwell Caves in the Forest of Dean, England. Clearwell has been a major quarry site for ochre pigments from the Roman period to the present day.

 

10. Mineral specimen: Cinnabar from Guizhou Province, China.  

11. Mineral Specimen: Crocoite is the mineral analogue of red lead. This sample is from Dundas, Tasmania, Australia.

 

12. Root of Rubia tinctorium, from which madder is extracted.

 

13. Paint trial of red ochre from Clearwell Caves, filled with chalk in a linseed oil medium.

 

14. Powdered X-ray diffractogram of Red Ochre. The sample diffracts the X-rays, producing a diffraction pattern unique to the material in question which can then be compared to an array of reference diffractograms. This technique was useful in confirming the presence of certain impurities found using polarised light microscopy.

Acknowledgements

Many thanks are due to the following people; Project Supervisor – Ruth Siddall; Martin Vickers – Senior Research Associate & Inorganic Section Laboratory Manager, UCL Chemistry; Martyn Towner – Lab Technician, UCL Chemistry; Zilu Liu – PhD student, UCL Chemistry; Jayne Dunn – UCL Culture; Alan Crease & Zoe Tomlinson – Sudbrooke Roman Villa; Jo Volley & Grace Hailstone – UCL Slade School of Fine Art.

This research was funded by the Laidlaw Scholarship Programme and undertaken by Alexa Marroquin and Jessica Manuel.