Conservation & Collections Care blog

Glass Iridescence – Deliberate or deterioration?

I’ve recently enjoyed making an interesting connection between our Roman glass collection and a beautiful display of Tiffany and Loetz glass that is part of the Frua-Valsecchi collection. You can see this for yourself in our Cypriot gallery.

Valsecchi glass display in the Cypriot gallery

Much of the Roman glass in our collection displays a pearlescent sheen known as iridescence. Although beautiful, and copied by 19^th and 20^th century glassmakers such as Tiffany and Loetz, this wasn’t deliberately produced by ancient glassmakers, it is the result of the deterioration of the ancient glass.

Iridescent glass vessel — Early Roman bowl found in Leukolla Cyprus, GR.101.1876

What is Roman glass?

The major component of glass is silica, found in sand. The melting point of silica is 1600-1713^oC, which is too high for production in simple glass furnaces (about 800^oC) so an alkali is added to reduce the melting point. In Roman glass this was soda, which is found in many naturally occurring salts. Lime is also needed to stabilise the material. This is found in many sands. Soda-lime-silica make a very stable form of glass.

Much Roman glass is slightly blue or green; this is caused by small quantities of iron in the natural materials used in glass making. Other colours could be produced by choosing particular sources of sands that contain different minerals.

Deterioration

Although largely stable, our Roman glass has had to contend with many challenges to survive to the present day. Vessels may have been physically damaged during use, at the point of burial or during excavation. Prolonged contact with water is also a significant challenge to the chemical stability and surface appearance of the material (take a look at a previous blog post where one of our conservation students worked on part of the glass collection).

Water leaches the alkali (soda) from the surface of the glass, especially in slightly acidic burial environments. This leaves behind fine layers of silica that can flake off the surface. The iridescence is purely a visual effect; in the same way that water droplets in the air cause rainbows, light is bent and split into its separate colours as it passes through the thin layers of deteriorated glass and air.

Surface of deteriorated glass showing pitting and flaking

Copying history

Tiffany – Louis Comfort Tiffany was an American artist and designer well known for his work in stained glass. In 1865 Tiffany travelled to Europe and visited the Victoria and Albert Museum (then the South Kensington Museum). Here he was struck by the colours of the Roman and Syrian glass collections, reflecting on the “rich tones” achieved without the use of paint. It is likely that Tiffany did not recognise the impact of deterioration on the appearance of this material.

Vase, Favrile glass. Louis Comfort Tiffany. Lent to the Fitzwilliam Museum by Massimo and Francesca Valsecchi.

The Tiffany Glass Company was established in 1887 in New York, but he was working with glassmakers at more than one Brooklyn based glassworks prior to this. In the early 1890s, Tiffany patented the Favrile glass making technique, which was heavily influenced by the appearance of ancient material. Multi coloured iridescent glass was produced by mixing different colours of glass together and spraying metal solutions onto the hot surface of the glass before the vessels were blown. The glassmaker Arthur J. Nash developed this method, passing it on to his son Leslie Nash. They kept the recipe a closely guarded secret that even Tiffany did not know.

Iridescent vase. Loetz, Austria. Lent to the Fitzwilliam Museum by Massimo and Francesca Valsecchi.

Loetz – A glassworks was established in Klostermühle (today called Klášterský Mlýn) in 1836. This changed hands several times until it was bought by Frank Gerstner and his wife Susanne Loetz in 1851. Loetz was the widow of a glassmaker and ran the business for 20 years after the death of her second husband in 1855. The business was then transferred to Loetz’s son-in-law Maximilian von Spaun in 1879. Working with the glassmaker Eduard Prochaska, he modernised the factory and developed new glassmaking techniques.

In 1897, von Spaun, saw Tiffany Favrile glass exhibited in Bohemia and Vienna. This inspired him to focus production on Art Nouveau style glass, which led to the most artistically significant and profitable period of the company’s history.

Being able to make this type of comparison of objects from widely separated time periods is one of the joys of working somewhere like the Fitzwilliam Museum. Come and take a look for yourself in our Cypriot Gallery.

Rehousing the Egyptian Organics

The Fitzwilliam Museum is well known for its large and diverse collection and the Department of Antiquities alone holds 27,000 objects. The public galleries represent approximately one tenth of this, with other objects packed away in storage areas. The best and most interesting of these are swapped onto display, many other objects, including small items such as pottery sherds and beads, are accessed by researchers whilst in storage. As Departmental technicians, one aspect of our job, is caring for the objects, both on display and in storage, and working alongside the conservators and curators to ensure that they are housed a suitable way, which will help guarantee their longevity and condition.
In the Antiquities stores, as with many museums, space is limited. With many objects kept in storage, it is an on-going job to rearrange both store and the objects, so that the collection can be best accommodated into the minimum amount of space, but remain accessible to researchers. A recent project that is part of this reorganisation is the Egyptian Organics.
As the name suggests, these are Egyptian objects, varying in types of organic material and design. They are extremely sensitive to changes in environmental conditions and insect pest attack, so it is best for them to be stored together, where we can keep a close check on these factors. They have been stored in temporary tray-stacks in several different places, and we were keen to get them repacked, documented and rehoused together.

How are we doing it?
There is quite a bit of work that will go into rehousing this material, it is not a simple case of just transporting them to a new cupboard or box. Each object is assessed individually through a multi-stepped process.

How the objects have been stored previously.

Up until now, the organics have been stored in these large trays. They are lined with inert foam and acid free tissue, however some objects were not as well supported as we would like and we were keen to refresh the tissue and reduce some of the cramped storage. Some objects had also become separated from their information or component parts.
Each object was taken out, photographed and assessed for its conditions and needs. Information on each object is imported into a spreadsheet, which includes details such as the museum number, a brief description of what the object is, what types of deterioration are present, whether there are old repairs, or metal components. We also gave it a condition grade out of 5, with 1 being in the best condition (similar to the condition of the objects out in the galleries) and 5 being the worst, meaning it might need immediate treatment.

Organics being photographed, documented on the spreadsheet and labelled up.

The museum number is usually written somewhere on the object itself. It may seem strange to permanently mark the object, but it is the best way to ensure the number remains attached, as labels and tags can easily fall off and become disassociated. These days, when marking an object we do it in a way that is reversible and not harmful to the object, but pieces that arrived in the collection in the past sometimes have the number directly applied to the surface. The museum number is how we identify the object, it links it to all its records and documentation, including information on when and where it was found, and how it came to be part of our collection.

An object like this would be hard to identify if we didn’t know its museum number. Luckily it has survived and is still legible.

This tells us that this object came into the museum in 1943, and it was the 5842nd object to be accessioned that year. It means we can easily access all the documentation and provenance for this object. By looking at the online database, we can find out that E.GA.5842.1943 is a figure of a Pygmy with a monkey on its shoulder.

Once you know what the object is supposed to be, it is a lot easier to recognise.
When all his information is recorded, and his label is attached, he is nestled into new acid free tissue paper and placed into a lidded plastic tray.

Even though his museum number is clear to read, giving him a second visible label means we do not have to handle him to check his number in future, thus minimising further damage.

Sometimes, due to the condition of the object (or the handwriting!) the legibility of the number can become a problem. If we are not sure of the number, we can check it against our Slip Books. For many, but not all of the objects, these Slip Book records were created at the time the objects were given a number. They contain lots of useful information, including drawings and sketches of the objects (as this was before cameras were readily used) which can be used to match the object correctly.

Object with its Slip Book entry and drawing.

These drawings are extremely helpful as we can determine what state the objects where in when they arrived and how they are faring now in comparison. It is important to note that the condition of most of these objects has barely deteriorated since they arrived at the Museum. Some objects, especially the tomb model figures, were found to have remnants of newspaper attached to them. As many of the Slip Books entries also make note of it, we can determine that it is likely this newspaper was wrapped around them, as packing material when they were first shipped to the UK after excavation. The newspaper has adhered itself to the surface of the object and became embedded within the grain, making it potentially a tricky (and long) job for a conservator to tackle.

Any object that does not have a number and we cannot straight away identify from the Slip Books, we assign an ‘Unknown’ number. Currently over 100 of these ‘unknown’ numbers have come out of this project.

All these unknown organics will have to be identified through investigation through both our online database and our Slip Books, some unfortunately might take a bit of work to identify!

However, as they are all now safely packed and documented, the conservators can get to work on any that require immediate treatment whilst we investigate!

Rehousing all these artefacts safely is only the first step. There are still many phases of conservation, research, and documentation to be carried out, along with more permanent housing for those that need stabilising. However they can now all be easily accessed and identified, as well as safely packed away.

Projects like these allow us to look at our collection in depth, building up a good picture of the nature and the condition of the objects. It is also one of the most enjoyable parts of our job, as you never know what you might come across next…

LEDs Part 1 Seeing things in a new light

How LEDs are now very much earning their keep

Gallery lighting – setting the scene

The best type of gallery lighting should be versatile, easy to calibrate, natural in appearance and ideally, environmentally compliant.

In recent years the advances in Light Emitting Diodes (LEDs)¹ have been little short of extraordinary. This is now an established lighting technology and is ‘absolutely where the future lies’, no ifs, no buts.

Here at the Fitzwilliam Museum most of the lighting, along with many other heritage institutions and art galleries, is predominantly by halogen incandescent² and to a lesser extent, fluorescent lamps. Although well-honed and now quite sophisticated, there are downfalls: significant energy usage, local heat production and certain reliability issues. Furthermore, when compared to LEDs, incandescent lamps have a pitiful lifespan and to compound matters, the sourcing of suitable parts has become increasingly difficult.

Replacing bulbs can be time consuming, disruptive, and in certain situations it is not always easy to undertake without an element of risk.

The average life expectancy of a traditional incandescent bulb will be around 5 years whereas by way of comparison, an LED will be closer to 100. These statistics alone reveal a startling disparity, and one that increasingly just cannot be ignored.

Recent advances in LEDs have seen a broader range of lenses available and perhaps of more significance, a greater accuracy with regard their colour rendition. So, when the cumulative power saving projections alone are taken into consideration, the argument against their implementation falls pretty much at the first hurdle.

Selection of LEDs

When selecting the type of LED for gallery use, four important factors should be considered carefully The colour rendition index, colour temperature, wavelength profile and light output or illuminance.

Diligent research and seeking guidance from an established supplier will pay dividends. See also: ‘LED Decision-Making In a Nutshell’ by James R. Druzik and Stefan W. Michaliski, August 2012, pp. 22, 23.

Colour Rendition Index (CRI)

The effect of a light source on colour appearance is expressed by the CRI index, on a scale of 0-100. Natural outdoor light has a CRI of 100 and is used by way of standard comparison.

CRI 60 – reasonable

CRI 70 – moderate

CRI 80 – good, reflecting colours ‘truly and naturally’

CRI 90 – excellent, a full and vibrant colour range (heritage organisations should be aiming for 90 plus).

Colour temperature

The colour temperature of a lamp can be used to understand how the light will appear to the human eye. Measured in degrees Kelvin (K).

Both natural and emitted electrical light (various types) will be composed of different wavelengths. Light, from whatever the source, will have a unique profile and in turn a ‘specific colour temperature’.

Warm light 2,700 – 2,800 K

Neutral light 3,500 – 4,000 K

Cooler light 5,000 – 6,500 K (simulates daylight)

Daylight at noon is generally cited as being around 5,600 K. However, in reality this figure will vary according to both the time of day and weather.

Wavelengths

Measured in nanometres (nm)

Ultra-violet³ (UV) light waves fall below 400 nm and is invisible to the human eye. The lower the wavelength, the higher the frequency and potentially, more damaging to museum collections. UV should be excluded wherever possible.

By contrast, Infrared⁴ radiation is above around 750 nm at the higher end of the scale and will produce heat. Heat speeds up chemical reactions and this becomes relevant when caring for collections with regard the rates of decay and degradation.

The graphs below compare old incandescent lighting in the Flowers Gallery with newer LED lighting in the recently refurbished Dutch Gallery.

Correlated Colour Temperature: 2750 K

Colour Peak: 766.77 nm

Lighting: Incandescent lamps (Halogen) and some filtered daylight

Correlated Colour Temperature: 3761 K

Colour Peak: 545.82 nm

Lighting: LED (predominant gallery light source)

Skylights: Fluorescent tubes minimal filtered daylight

Wavelength profiles captured with a Spectrometer (GL Optic’s GL SPECTIS 1.0 touch) January 2017.

Light Output – Illuminance

Measured in Lux⁵

The illuminance considered appropriate for most gallery spaces will be dictated by both addressing audience need and the various sensitivities of the collections displayed (the material type, make-up and overall condition).

Taking a light reading⁶ in the Dutch Gallery. Oil on panel (detail) by Abraham van Calraet, 1642-1722.

Light levels and exposure should be carefully monitored and ideally logged, since light damage to museum objects is often subtle; the effects are cumulative and crucially, any change inflicted is irreversible.

By way of an example see the drawing below where the cut away top mount shows just how drastic the change can be.

Black and white chalk drawing on a coloured paper by Walter Sickert, 1860-1942 (detail).

In this particular case, the coloured paper support was originally and entirely, a greenish blue. The colour shift from green to brown, where the drawing has been exposed to light, alters both the look and quite possibly, the intended context. Fortunately, such extreme examples are rare within museums and as conservators, we always endeavour to keep it this way.

A computer generated overlay gives an impression of how this drawing would have originally looked.

Intelligent lighting design: Creating a sense of theatre

With carefully calibrated light levels, directional beams and consideration to the colour balance (within the range of whites) the impact of intelligent lighting can be little short of ‘transformative’. As such, many of the more informed galleries are now making good use of specialist lighting designers.

An example of exhibition lighting here at the Fitzwilliam Museum:
Degas: A Passion for perfection (2017).

Wall mounted art works and a cased table top display, carefully lit.

Bronze Spanish Dancer (foreground), posthumous cast, by Edgar Degas.

In the above two examples both the needs of the museum objects and the overall gallery lighting has been planned.

The recently refurbished Dutch Gallery (2014)

As part of a recent refurbishment project in one of the galleries here at the Fitzwilliam Museum, various lighting modifications were considered. The museum adapted – it embraced change and now this particular gallery is predominantly LED lit.

The Dutch Gallery with a c1690-1700 Flower Vase (foreground) hosting, in this case, some convincing silk flowers. ⁷

Displaying a mixture of museum items within the same gallery space can present certain challenges since each item type will have a different tolerance.

As such, the most sensitive object will tend to dictate the parameters. In this particular gallery the light levels falling on the displays range between 80 – 130 Lux (UV excluded) and are fully compliant with current standards.

The Dutch Gallery (above) is a wonderful example of just how beautiful a space can become with careful consideration and resourcefulness. LED’s are now very much part of the conversation and with regard to a transition, it is not a question of if but when. For my money – the sooner the better.

Seeing things in a new light – how LEDs are now very much earning their keep. Part 2 will follow in the coming months. Various pieces of studio equipment making use of LEDs will be further investigated and discussed.

We haven’t finished talking about him… Henry VIII’s book is on the bench for some treatment

Henry VIII of England continues to attract attention. This time it is not about one of his many wives but about a book he wrote, the very book which granted him the title of Defender of the Faith, a title still assigned to British Sovereigns today. Henry VIII was a highly educated man and in the years before he turned against the Pope and the Church of Rome, he wrote a treatise called The Defence of the Seven Sacraments against Luther. The book is a theological treatise, dedicated to Pope Leo X, defending the Catholic Church against Martin Luther’s attack on Indulgences, and was printed in London in 1521.

The Fitzwilliam Museum’s copy

The Fitzwilliam Museum’s copy of the book is one of 27 copies that were sent to Rome by Henry to be distributed among the Cardinals of the Church after approbation by the Pope¹. As we are currently working towards an exhibition on Money, Image, and Power in Tudor and Stuart England (spring 2019), the book was brought up to the conservation studio, and this is when the exciting detective work started. In fact, the book has a number of interesting physical features which I tried to unravel, helped by my curatorial and conservation colleagues Suzanne Reynolds and Edward Cheese, in order to choose the most appropriate conservation treatment and extract as much information as possible about its history.

The authentic features

I was able to validate several authentic features of our copy, the large signature of Henry VIII at the beginning and end of the text being the most obvious evidence. The sixteenth-century full leather binding is blind-stamped with the Royal arms and the Tudor rose in a double panel. These stamps are attributed to the London binder John Reynes² and prove the authenticity of the binding. The title page is decorated with an elaborate woodcut border designed by Hans Holbein (1497-1543) which has been recorded by Gordon as part of the original features of the first edition of the treatise³.

Other features

Other features bear witness of the life of this copy and tell us about its owners, its condition and its uses.

Signs on the binding

The front board shows an inscription that has been scratched in the leather. We can read REX ANGLIAE IN LVTH meaning “The King of England against Luther”. The foredge has been inscribed with the title, along with an intriguing sign. This symbol is hard to identify and we came up with two suggestions of what it could be: a cross-bearing orb or a pomegranate. Please get in touch if you have seen this sign used on other books – there are possible links to Queen Catherine of Aragon.

Inside the book

The pages have been numbered by hand, and the running titles have also been added by hand by a reader comfortable with the Latin of the text, using an elegant humanistic script. This reader also annotated the text extensively.

The front pastedown

A nineteenth-century manuscript note on paper is adhered to the front pastedown. It is signed by Samuel Woodburn (1780/5-1853, art dealer and expert on Old Master Drawings) who explains that he bought the book from Signor Romanis at Rome in 1818. Napoleon’s invasion of Rome (1798) had a powerful impact on the Vatican Library as well as its manuscripts. Book dealers coming from England and other countries followed the army and acquired many books and illuminated cuttings. If Samuel Woodburn’s note is true, the book was purchased by Signor Romanis when several of the books belonging to the late Pope were sold by order of the French Army.

Remains of a former reback

One final feature. When removing the existing leather spine repair, blind-tooled brown leather remains were found underneath the original leather along the joints, suggesting a former reback. The patterns that are still visible indicate that the leather came from a fairly large late fifteenth – or early sixteenth-century binding with a central panel of triple-lined lozenges framed by foliate ornaments. The stamp used for these ornaments and the style of the layout is very similar to one recorded by Basil Oldham in English Blind-Stamped Bindings⁴, confirming the date of the re-used leather.

Features identified in Basil J. Oldham’s book

Conservation treatment

Let’s get on with some conservation treatment now!

The book was in fairly poor condition. It had been rebacked at least twice and the last reback was creating tensions to the book. Boards were distorted, corners were worn, the front endleaves were detaching, the large strip of glassine paper supposed to support the title page was falling off and the pages were dirty and torn around the edges. There was definitely room for improvement!

Here are the illustrated stages of the conservation treatment:

Removing the current reback, removing the thick layer of hard animal glue from the spine, and reinforcing the sewing with Japanese paper linings in the panels and linen braids over the sewing supports.

The glassine paper was removed mechanically.

Tears were repaired and losses filled with toned Western and Japanese papers.

Corners were reinforced and reconstructed. They were then covered with toned archival leather.

The waste parchment guard hooked around the front endpapers was cleaned so that the thirteenth-century manuscript writing could be revealed.

Margins were cleaned with a smoke-sponge. New back-bead endbands were sewn to reinforce the sewing. The detached leaves were guarded with Japanese paper strips and sewn back on to the textblock over the extended sewing supports using linen thread.

Boards were re-attached using the extended sewing supports. Finally, the book was rebacked with toned archival leather and housed in a bespoke drop-spine box.

Thanks to this collaborative detective work and the conservation treatment that followed, the book is now stable and well documented, available to researchers and ready to go on display!

Special thanks to Assistant Keeper Suzanne Reynolds for all her help in untangling the many mysteries of the book and bringing academic support to the project.

Walking on eggshells: conservation treatment on Roman glass

By Adelheid Hansen, Conservation Intern in the Departments of Antiquities and Applied Arts at The Fitzwilliam Museum. Graduated from the Ceramics and Glass Conservation Programme at West Dean College.

In conservation, an important principle is to protect an object from (further) damage. Conservators often have to find creative methods to ensure an object is not harmed by treatment.

One of my tasks as a conservation intern at the Fitzwilliam Museum in Cambridge was to conserve a 14 centimetres high Roman glass unguentarium (thought to have been used for perfume or oil), which was found in Cyprus and had entered the museum collection in 1888.

The unguentarium had many issues:

There was a kidney-shaped area of loss with a sharp piece sticking out (fig. 1)
There were several running cracks, one running halfway around the body! (fig. 2)
There was iridescence. Iridescence, as beautiful as it can be, is a sign of degradation and can detach itself from the glass surface in the form of flakes
There was dirt inside
And last but not least, due to glass degradation, the remaining glass was extremely thin, as thin as, or even thinner than, an eggshell.

Fig. 1 Unguentarium before treatment, front side, showing kidney-shaped area of loss

Fig. 2 Unguentarium before treatment, reverse side, showing running crack halfway around the body

Roman glass usually consists of a mixture of sand, soda and lime. When buried in the earth and in contact with water, the soda can dissolve and leach out, causing degradation of the glass. When left long enough, the whole object could disintegrate and disappear.

Treatment plan

The running crack needed stabilising and also the sharp piece sticking out needed protection.

When glass is that thin, it is not an option to introduce an adhesive into the running crack, because it can make the crack lengthen and even split the vessel into two halves.

Therefore, we decided to try to stabilise the unguentarium by attaching a fill from the inside to the missing area. This way, the cracks would be supported and also the dirt on the inside would be protected. Dirt can tell a great deal about the history of an object, for instance about the area where it was found, or it could hold a residue of the previous contents of the unguentarium. When removed, this history is lost; therefore, we decided that the dirt should not be removed.

Japanese tissue with a coating was chosen to make the fill. Japanese tissue is strong and lightweight, so the weight of the fill would not cause further damage, and the coating would provide support for the Japanese tissue. This way it would be possible to make a strong and thin fill.

But since the glass was so extremely thin, no mistakes were allowed and attaching the fill had to be right the first time. Therefore, it was necessary to practise on another object.

Practice

Finding a replacement object to practise on was not difficult, because the discussion about the glass being thinner than an eggshell inspired me to practise on an actual eggshell. After a few attempts resulting in broken eggshells, I managed to carve a similar shaped hole in the eggshell, to the hole in the unguentarium, using a scalpel (fig. 3).

Fig. 3 Shape carved out of eggshell with scalpel

I tested two adhesives to use as a coating on the Japanese tissue. Klucel G, a water-soluble adhesive, could not provide enough rigidity for the Japanese tissue. Instead, a 10% w/v solution of Paraloid B72 in acetone was used to make the coatings (fig. 4).

Fig. 4 Solution of 10% w/w Paraloid B72 in acetone

Next, I needed to develop a method for how to shape the Japanese tissue. Fortunately, I found a bottle in the lab that had a similar curve to the missing area of the unguentarium. I then applied de-ionised water to a piece of Japanese tissue with a glass pipette. The wet Japanese tissue was placed on the glass bottle and I carefully manipulated it in such a way that there were no creases in the paper (fig. 5). Care was taken not to stretch the tissue too far, as this would cause thin sections in the tissue. The bottle was placed on a radiator to accelerate drying time.

Fig. 5 Piece of Japanese tissue drying on glass bottle

After the Japanese tissue had dried, I carefully removed it from the bottle. The tissue now had a curved shape. I then placed the now curved Japanese tissue on a Melinex (polyester film) sheet and applied a solution of 10% Paraloid B72 w/v in acetone with a glass pipette (fig. 6). After curing, new layers of the Paraloid B72 solution were applied in the same way, until the Japanese tissue had the right strength.

Fig. 6 Applying layers of Paraloid B72 with glass pipette to shaped Japanese tissue

I cut the curved and coated Japanese tissue slightly larger than the missing area. Unfortunately, it proved to be impossible to insert the fill in one piece, and therefore I cut the fill into two halves.

Fig. 7 The fill is too big to be lowered into the egg in one piece

The fill had to be lowered into the unguentarium and lifted up in order to be able to bond it behind the missing area (the surface on the outside of the bottle was too fragile to have adhesive applied to it). Therefore, I attached two sections of string to each half. First, I tested masking tape to attach the strings to the fills (fig. 8). However, masking tape would be difficult to remove while the fills were adhered to the glass. Even the slight force needed to remove the tapes could cause the glass to break. I also could not use solvents to remove the tapes as this could compromise the coating of the fill.

Fig. 8 String attached with masking tape

I then tested a solution of 5% w/w Klucel G in de-ionised water to attach the strings (fig. 9). Klucel G is soluble in water which would not compromise the coating, however, Klucel G proved not to be strong enough. Therefore, cyclododecane was used to attach the strings. Cyclododecane is a wax that will sublime over time and disappear, so no solvents or force would be needed to remove the strings. They could simply be left until they fell off.

Fig. 9 Strings attached with Klucel G

For this part of the process, I needed an extra pair of hands. Julie Dawson kindly offered to help me. We frayed the ends of the strings to enlarge the area of contact. Cyclododecane was heated au bain-marie under extraction and was applied to the frayed strings on the fills with a brush. Each half of the fill now had two pieces of string attached and was ready to be attached behind the missing area.

The first half of the fill was lowered into the egg and then raised by gently pulling up the strings. One of us used acetone on a small brush around the edges of the fill to activate the Paraloid B72 and to adhere the fill to the egg, while the other kept the strings being pulled up. This process was repeated with the second half of the fill (fig. 10).

Fig. 10 Strings attached with Cyclodecane, fill complete

Fig. 11 Tools used for egg-practice

Treatment

The method proved to be successful and could now be executed on the unguentarium. Because all the stages of the treatment were rehearsed on the egg, attaching the fill to the real object went smoothly (figs. 12 and 13).

Fig. 12 Unguentarium during treatment

Fig. 13 Unguentarium during treatment

The end result was a stabilised unguentarium (fig. 14).

I thoroughly enjoyed the process of testing various options on an eggshell and finding a solution that was beneficial to the unguentarium. I am very grateful to the conservation team of the Fitzwilliam Museum for giving me this learning opportunity.

Fig. 14 Unguentarium after treatment

Acknowledgements to:

Jennifer Marchant, for supervising my project
Julie Dawson, for helping me with the cyclododecane
Elsbeth Geldhof, for teaching me about the many uses of Japanese tissue in conservation
Edward Cheese and Gwendoline Lemée, for providing the Japanese tissue.

Lantern Project in the Founder’s Entrance (Part 5)

What lies beneath…

As with many conservation projects, new discoveries are made as work progresses.

The contractors for the lantern repairs, Brown & Ralph, have provided an explanation as to what happened when they looked below the surface. What was revealed showed why this project is so crucial for the future of this historic building:

“Having removed the original weather-proofing from the lantern, several areas of suspected decay to the timber structure beneath were identified. Upon further investigation, it was found that some timbers were rotten and the structure weakened in these areas. This is thought to be the result of long term minor water ingress.

“Once the areas were identified, the Museum’s Structural Engineer worked with carpenters from Brown & Ralph to design a repair to the timber structure. This involved propping critical load-bearing timbers, cutting out rotten timber, forming joints and ‘letting in’ of new timber.

“The repairs were all worked out individually to cause as little interference as possible but maintain maximum strength throughout the structure. B&R were able to carry out all the repairs employing traditional timber joints. The replacement timber (some with sections as large as 300mm x 150mm) was selected from a trusted saw mill and used slow grown Douglas Fir to mimic the timber used when constructed originally.

“As a result, the structure is back to full strength whilst maintaining the original aesthetics. It has since been re-boarded with similar Douglas Fir.”

When fashion transforms the truth

As part of Cambridge’s Festival of Ideas 2017, I took part in a series of behind-the-scenes talks on how we investigate the ‘true’ nature of museum objects. As the event was so successful and attendees showed a lot of interest in the subject, this blog post is aiming to share the story of the objects I discussed on that occasion.

What secrets or lies can we unveil, by which means can we do that, and how far can we go into our understanding of past practices? Some objects lead us into exciting journeys and this is the case of two manuscripts fragments from our collection (MSS 293a and 293b¹).

These two beautiful and quite peculiar illuminated fragments come from the Royal Monastery of St Thomas in Avila, Spain, and were presented by the Friends of the Fitzwilliam Museum in 1918. By taking different approaches – those of a curator, a conservator and a research scientist – to investigate the truth of these objects, we can retrace their story and reveal some of their secrets.

Historical context and iconography

The description of the image is the first step in our investigation and already gives a lot of information. First we can see that the main part of each image is a large letter: we can identify an ‘M’ and a ‘D’. These are enclosed within composite floral borders containing birds, animals and grotesques, as well as the arms of Castile and Aragon and the devices of the Spanish sovereigns Ferdinand and Isabella, the yoke and the bundle of arrows respectively.

Questions arise already and we start wondering what text these two initials introduced, from which manuscript(s) the images were excised, and what is their context. The catalogue description ² suggests that the initial ‘M’ would have introduced Psalm 131 (the first psalm for Thursday Vespers) and the initial ‘D’ would have introduced Psalm 114 (the first psalm for Monday Vespers). This type of initial, “shaped and surrounded by densely populated foliage on highly burnished gold grounds, contained within frames inscribed with phrases from the accompanying text”, is, according to our curator Dr Stella Panayotova, “representative of Castilian illumination of the last quarter of the fifteen century which agrees with the internal evidence of the royal arms and devices.” The presence of the arms of Castile and Aragon as well as Ferdinand and Isabella’s devices does indeed give us a lot of information about the time of creation of these images. The two kingdoms of Castile and Aragon were united by this royal couple in 1479; in 1492, the pomegranate (not present here) was added to the royal arms to mark the conquest of Granada. We can therefore conclude that these images were created between 1479 and 1492.

Looking more carefully, we notice the strange layout of the borders. We can see that some of the animals are upside down and some of the drawings are incomplete. We are also aware that this sort of image with such large borders so closely attached to the large initials on all four sides is not commonly seen in illuminated manuscripts. Also, we have two large initials but no other text, so we start asking questions about what happened to these objects and how and why such images came to look the way they do today. At this point we have to start looking ‘beyond’ the image, at the materiality of the object: what is it made of and how can we explain the size and composition of the images?

Conservator’s approach

Last year MS 293a arrived at the conservation studio because it needed some treatment. The fragment was lined with cardboard which was acidic and causing tensions in the parchment. Both of these features were damaging the object.

When MS 293a arrived at the conservation studio I followed the usual starting procedure of figuring out what I was dealing with. The catalogue description of the object gave me a good idea of the date of the illumination fragment and its iconography, but very little was written about its materiality.

Using raking light was the most effective observation method to understand the composition of the object. We can see the texture of the surface, giving information about the thickness of the paint layers and the way gold was applied. Raking light also highlights the presence of separate pieces of parchment. So not only is this a fragment from an illuminated manuscript, but it is an assemblage, a collage of several fragments. This explains the very complex completed image, acting as an individual painting.

Cutting illuminated manuscripts to create new ‘beautiful’ images was a fairly common practice in the 19th century and demonstrates the changing attitudes towards illuminations over time. Mid-19th century revival of interest in Gothic art led to the invasive exploitation of illuminated manuscripts where illuminations were cut and reused in a different context and format: MS 293a was assembled to stand as a painting. It is, as Stella Panayotova writes in the catalogue of the COLOUR exhibition, “a damage inflicted upon illuminated manuscripts, motivated paradoxically, by admiration for them as works of art”.

Backing removal

As mentioned before, the collage was supported by an acidic cardboard. It had been glued with animal glue and stuck firmly onto the board.

The illuminated cutting is painted on parchment which is made of animal skin and is both a very durable but also very reactive material. Parchment becomes stiff over time and reacts hugely to the relative humidity of the surrounding air so tensions can appear when the parchment is forced into a certain shape. My task was to remove the backing and mount the object to keep it safe and stable.

I had to remove the backing board layer by layer in order to reduce the risk of distorting the illumination which could disturb the paint layers. During the process the collage was laid onto a large piece of felt so that the illumination was not crushed. A thin layer of paper was found at the back of the collage and was probably the sheet of paper on which the pieces of the collage were originally adhered. We decided to leave it in place in case removing it would loosen the pieces. However, getting so close to the back of the illumination was intriguing so we looked at the object with transmitted light (now that it was fairly thin) and were able to make out large black Gothic letters. These letters are written on the back of the initial fragment. This was a magical moment and confirmed that the initial belonged to a very large manuscript.

MS 293a through transmitted light after backing removal

We had already so much information and could be fairly confident in attributing the illuminated initials to a Choir Psalter, written in Latin and originating from Avila in Spain in the late 15th century.

We also found out via observations under natural light and raking light that the collages were made of 8 fragments (MS293a) and 3 fragments (MS293b) respectively. Our curator was fairly confident in attributing the floral borders to the same illuminated manuscript as the initials. We could now go further in our understanding of the object and being able to reveal how the ‘artist’ who made the collage achieved the final composition. This is where our research scientist comes in.

Scientific approach

Collaboration with Dr Paolo Romano and Claudia Caliri from the LANDIS Laboratory in Catania (LNS-INFN and IBAM-CNR), allowed us to analyse MS 293a with a cutting-edge macro-XRF scanner, which they shipped here all the way from Italy! The spectral images obtained were interpreted by our research scientist and here is what they revealed:

The elemental map for iron (Fe-K) shows the presence of iron in various areas. The obvious place where we can see iron is in the gilded areas because iron is a constituent of Armenian bole, which would have been used as the ground layer for the application of gold leaf. However, we can also see what appear to be letters throughout the centre of the image. By flipping the image over (see image below) and adjusting its contrast we realise that these are indeed letters, written in iron-gall ink on the other side of this parchment page. Careful observation allows us to start reading the text hidden behind the collage.

MS 293b, elemental map for iron (Fe-K) flipped left-to-right

The false-colour elemental map for zinc, chromium and cobalt (in red, green and blue, respectively ) reveals the presence of elements, all of which are characteristic of ‘modern’ pigments. Combining this information with other analytical data, we can identify the presence of zinc white, cobalt blue, barium chromate and a chromium-based green, all of which were first manufactured in the first half of the 19th century. This information, together with the absence of any pigments manufactured after 1850, suggests that the collage was assembled, and the image retouched, probably in the 1840s, in line with the 19^th-century practice of excising illuminations from manuscripts to create new art objects.

MS 293a, false-colour elemental map for zinc, chromium and cobalt

Conclusion

Collaboration between curator, scientist and conservator helped to retrace the origins and the story of these collages and to document them. These objects are new valuable objects, made of ancient valuable fragments. We won’t undo the collages because they document historic practice on top of being a new artwork. Besides, there is currently no parent manuscript so re-uniting the fragments is not possible – and if it was, digital methods could allow us to reunite fragments from all over the world by use of online digital tools, for example the IIIF (International Image Interoperability Framework). Separating the pieces could also damage the parchment and the paint layers, and having individual fragments without a specific place or use for them wouldn’t be appropriate.

Revealing the truths of an object is so important because we can’t undo what has been done for various reasons explained previously. However, we can document the object and share the information. One day, perhaps, through sharing information, we will find more related fragments that will feed into our understanding of the object itself and the historical practices involved and we may even be able to start reconstructing the illuminated manuscript that was once proudly standing in the Royal Monastery of St Thomas in Avila.

This cutting from our collection gives an idea of the scale of a Choir Plaster and how the fragments of the collage could have been laid out on a page. This is MS 197, from a 15th-century Italian Choir Book (see catalogued information’s here). We can see the large initial, the floral borders, the coat of arm and large black manuscript letters.

With special acknowledgement to Dr Paola Ricciardi, Fitzwilliam Museum’s Research Scientist, for her input with scientific research and imaging and for her help with co-writing this blog post.

Lantern Project in the Founder’s Entrance (Part 4)

Work on the Founder’s Entrance lantern is in full swing. The internal plaster conservation works were completed last month, along with the conservation cleaning. And Tobit Curteis Associates have given us the below update on the conservation paint treatments they have been working on.

The scheme of decorative plasterwork and polychromy in the entrance hall is among the finest of its period in the country. It was conserved for the first time at the turn of the millennium at which point it was found that, although the surfaces were extremely dirty, having lived through the Industrial Revolution, the condition of the plaster and paint work was generally very good. Cleaning and conservation revealed the decoration in all its richness and had a huge effect on the appearance of the hall as visitors enter the museum. Some 17 years later, the conservation survey showed the condition still to be generally very good although there had been additional accumulation of dust and dirt as well as some minor flaking and loss resulting from unstable environmental conditions.

The aim of the current conservation project therefore is to record and document the condition of the decoration and to carry out limited stabilisation, cleaning and retouching. The team of conservators, working with Tobit Curteis Associates, has now been working on the conservation of the polychromy for three weeks and the work is progressing well. Most of the treatment carried out by Tobit’ team in 1999 and 2000 has remained stable and the areas of more recent damage have responded well to treatment. The planned relighting of the entrance hall will further improve its appearance so that visitors can again experience the decorative scheme much as the architect originally intended.

Tobit Curteis Associates

Work Placement – Manuscripts and Printed Books Conservation Studio

In the summer I spent four brilliant weeks with the conservation team in Manuscripts and Printed Books. Edward, Gwendoline and all the staff at the Fitzwilliam generously gave their time and knowledge to make my placement at the Museum enjoyable and an invaluable experience as part of the MA conservation course that I am studying at Camberwell College of Art. I completed a number of practical projects, including rebacking of cloth case bindings and the repair of architectural plans of the Founder’s Library.

Fitzwilliam Museum No 60, 1847 showing the Chimney Piece for the South Library

The architectural plans, mostly from 1847, were graphite and pen and ink on drafting paper – a transparent paper made by adding oil which, after many years, has degraded to make the drawings very fragile and brittle. This was a satisfying collection to work on as the drawings were taken off poor-quality backing paper, carefully flattened, and repaired with fine Japanese handmade paper. Finally, to make them easier to handle and visible on recto and verso, individual folders were made from Melinex®, an archival polyester film. For this I also got to learn to use some new pieces of equipment – the polyester sealing machine and ultra-sonic spot welder. With these I was able to make folders around the object, as you can easily seal as many sides around the enclosure as you need. It meant I could also get a wide enough border to prevent the corners of the drawings from being damaged in future. The ultra-sonic spot welder allows the old label to be displayed alongside the drawing in the same folder without the need for attachment to the Melinex®.

The Founder’s Library at the Fitzwilliam holds a wide variety of different bindings on rare examples of manuscripts and printed books. The cloth case binding rebacks I completed were for two volumes of the Arabian Nights Entertainment and an edition of Augustinus printed in 1490. Although all three bindings were nineteenth-century cloth case bindings, the damage and therefore the conservation treatment were each unique. I like the problem-solving element in taking a similar technique of creating a hollow-back binding to give durability and allow for the original spine to be put back in place, but taking different approaches depending on how he original structure was damaged and how that dictated access into the structure for repair with minimal disturbance to each binding. For instance, Volume II of the Arabian Nights had spilt endpapers making this an entry point to the spine whereas the endpaper joints in Volume I were in good condition so it was important to not damage these during treatment – access was through the spilt down the length of the cloth joint. The Augustinus had a whole piece of the spine detached and revealed a piece of printed paper used as a spine-lining that it was important to keep and protect in case it holds information worth future investigation.

Arabian Nights Entertainment Volume II, 4G17

Arabian Nights Entertainment Volume I, 4G16

Being in the studio meant that during the four weeks I was able to observe and learn from the diverse range of conservation treatments going on. Work on parchment was a new technique and material for me so I enjoyed being able to have a go at reproducing some historic and current repair processes. The area of printed books and manuscripts encompasses a range of different materials and techniques, with the additional consideration that bindings need to ‘work’ mechanically every time the volumes are consulted. I started a model example of a herringbone sewing: making this really helped me to understand how sewing on double cords works and locks each stitch in place for a very strong and flexible structure. As well as being ‘working’ objects, books and manuscripts are artefacts that need looking after and handling with respect. I think one of the factors in helping communicate this is the beautifully handcrafted bespoke cases and boxes made for items in the collection. The books need to fit exactly to protect them. The clam-shell box I made has double thickness on the walls making them very strong; lined with conservation board, they create a non-damaging environment within.

What made my placement particularly enjoyable was all the people who took the time to show me around and share their knowledge. I am grateful to have had the opportunity while in Cambridge to visit the wider conservation community there, from current students, Anna and Elisabeth, giving me a tour at the Hamilton Kerr Institute, to Jim and the team at the University Library showing me the many and varied conservation projects that they have going on, and to Bridget, Françoise and Claude at the Cambridge Consortium and Nicholas Bell at the Wren Library, Trinity College. I found the diversity of different projects being undertaken in all the conservation studios and treasures held in the collections fascinating.

Each of the departments at the Fitzwilliam also took time to show me the different projects that they have ongoing and their collections, from which a lot of exciting research is generated. It was good to see something of the day-to-day work of departments dealing with new acquisitions, items for loan and exhibition and challenges of storage and building constraints as well. I learnt a lot, and will continue to do so through my final year of study and beyond.

Finally I’d like to thank Edward Cheese and Gwendoline Lemée for making it an absolute pleasure to be in the conservation studio and taking the time to teach me many new skills. The experience went far too fast!

Preparing for ‘Flux’: Object Processing on a Large Scale

In the past year, the Applied Arts team has faced a monumental task: processing a group of 360 newly acquired pieces of Parian-ware (or Parian) porcelain, predominantly busts, in preparation for an upcoming exhibition. Most were dirty and many were separated from their original bases, which had become jumbled up. The scale of the project required that we think differently about how to care for the objects, finding an efficient way of processing them while respecting individual conservation needs.

The Glynn Collection of Parian-ware was acquired by the Fitzwilliam Museum in 2016 as part of the Acceptance in Lieu of Inheritance Tax scheme. Largely featuring busts of Classical characters and Victorian public figures, it provides an important insight into lives deemed worthy of commemoration in 19^th-century England.

Acquiring such a significant collection opened up exciting possibilities for interpretation and display. The exhibition Flux (opens March 2018 in the Octagon gallery) is guest-curated by the artist and historian Matt Smith. As well as producing his own art, predominantly in clay, Matt has extensive experience of curating museum collections, often re-interpreting them from the view of an outsider. Flux will make use of his own unconventional Parian-ware (most fascinatingly produced in black Parian!) highlighting the Fitzwilliam’s historic collection and making it more relevant to a contemporary audience. The Flux display will accompany a major exhibition of studio pottery, Things of Beauty Growing, which will showcase ceramics sourced by the Yale Center for British Art, in New Haven, USA.

Parian-ware is named after the Greek Island Paros, known for its white statuary marble that was popular in the Classical world, which the porcelain imitates in appearance. Parian was a development of the biscuit (or bisque) porcelain used primarily by factories in France, such as Sèvres, to produce small-scale statue-like figures. This was developed further by porcelain manufacturers in Staffordshire, Britain, in the mid-19^th century in order to give the surface a more reflective, marble-like finish. The slip-casting method, where liquid porcelain is poured into a detailed mould, allowed mass-production; making affordable, marble-like statues and busts available to middle-class Victorian homes. Parian was popularised by many British factories, right through to its decline in the early twentieth century. It was produced by many famous names such as Coalport, Wedgwood and Copeland. Factories competed with one another to obtain the finest Parian ‘recipe’. This has resulted in the many pieces within our collection having very different finishes, textures and weights. They vary greatly in density, porosity and colour: there are many shades of white and a few are tinted with coloured slips. Several busts are mounted on separate Parian bases, attached with threaded metal dowels. All these aspects need to be taken into account when treating each object.

The considerable size of the Glynn Parian-ware Collection made it necessary to develop a methodology that would allow streamlining the process of accessioning and conserving the porcelain in preparation for the Flux exhibition. The collection has occupied most of the available work surfaces in the department for much of the year, and clearing space was a priority. The first step required the combined effort of Departmental Technician Timothy Matthews and Research Assistant Helen Ritchie, who examined, photographed, measured and described the objects one by one, recording all information on a spreadsheet and eventually assigning each a museum accession number.

The condition was assessed by Penny Bendall, an independent ceramics conservator, who identified which objects required more complex conservation treatments, such as the reattachment of broken parts, removal of old repairs and re-mounting on bases. The vast majority just needed cleaning in order for them to be appreciated properly and to be made suitable for public display. The porcelain had more than likely been stored in different conditions and cared for in different ways by different owners. While many of the larger busts appeared to have been kept outside, their surface weathered and discoloured by accumulated dirt, smaller statues were far cleaner. Timothy Matthews and Assistant Conservator Flavia Ravaioli removed surface deposits using an enzyme-based detergent that activates in warm water. You will see from the photographs that a small amount of detergent was initially applied by brush and left on the objects’ surface for a few minutes to allow the enzymes to work. The detergent was then worked over the surface with the brush, taking care not to scratch the surface, until all the dirt had lifted. This was followed by thorough rinsing with specially-filtered water to remove all residues of the detergent. Finally, the porcelain was dried with soft cloths, then left in a warm place until completely dry.

When cleaning Parian-ware, we are very mindful of areas of restoration, the porosity of the surface, the presence of metal elements and old labels. When encountering a restored piece of Parian, we do nothing more than dust it with a dry brush, as using detergent and water could weaken or remove previous joins or restorations. A small handful of restored pieces were cleaned with acetone on small cotton wool swabs to allow more localised application.

Once clean, the objects were labelled with their accession number, photographed, and stored away to await display in the spring. So far 260 pieces have been completed. Only 100 more to go!

Timothy Matthews, Departmental Technician

Flavia Ravaioli, Assistant Conservator