A Heavenly Transformation – The Treatment Continues…

Jan Cutajar

Check out the previous posts in the series here, here, and here!

Our last blog post on the treatment of the Norfolk Museums Services angels dealt with some very satisfying flake relaying on Angel A. In this new episode, we shall delve into the treatment of Angel B (shown below in case your memory needs jogging), which had suffered a more severe case of surface delamination than its counterpart. Indeed, the delamination had reached such a severe state that even slights movements of the angel within its packaging resulted in notable loss of gilding!

Angel B, more affectionately known as Gabrielle. Courtesy of Norfolk Museums Service, T1878333.

Angel B, more affectionately known as Gabrielle. Courtesy of Norfolk Museums Service, T1878333.

For this reason, an intensive rescue operation took place earlier this year over three, wintery January days, with the aim of stabilizing the angel so that it may be removed from its packaging and be treated in a similar manner as Angel A. An enthusiastic team comprising of the author, Letty Steer and Dae-Young Yoo was put together and led by a motivating Claire D’Izarny-Gargas.

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The team members hard at work – above, from left to right, Dae-Young Yoo, Letty Steer & Claire D’Izarny-Gargas; below, from left to right, Jan Cutajar, Dae-Young & Letty.

The team members hard at work – above, from left to right, Dae-Young Yoo, Letty Steer & Claire D’Izarny-Gargas; below, from left to right, Jan Cutajar, Dae-Young & Letty.

Given the condition of the angel, it was slightly (if not very!) daunting to actually even consider touching the angel. The first step, therefore, was to develop a method of stabilising very loose flakes. After several initial trials, it was found that the best method, given the time frame we had to work in, was to apply a Japanese tissue paper facing (adhered directly with a 2% w/v solution of Klucel G in isopropanol, a hydroxypropyl cellulose adhesive commonly used with organic materials), which was then heat-activated using the heated spatula. This step allowed the gilding flakes to be slightly re-shaped in the process before relaying. You can see these facings in the pictures above – here are some more detailed shots of the procedure.

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Applying the Japanese tissue facing using 2% w/v Klucel G – where possible, the areas of flaking were cleaned first, as can be seen. Sometimes though, this was not possible and facing was applied directly to severely flaking sections.

Applying the Japanese tissue facing using 2% w/v Klucel G – where possible, the areas of flaking were cleaned first, as can be seen. Sometimes though, this was not possible and facing was applied directly to severely flaking sections.

The same procedure used to relay flakes on Angel A was then used, applying solutions and heating through the paper facing, which was possible due its fibre-thin nature. Once the gelatin (5% w/v in deionised water) had set hard after 5–10 minutes from heat-activation, the facing was removed by first moistening it with lukewarm deionised water and then peeling it off at a 180o angle with a pair of pointed tweezers. Any clean-up of excess gelatin or paper threads could then take place with warm water swabs.

Here’s an example of the complete treatment procedure: (1) flakes before treatment; (2) facing applied; (3) application of 50% IMS and gelatin, followed by heat activation; (4) after setting, the facing is removed with a warm, wet swab; (5) tweezers are used to pull the facing gently off; (6) the area after treatment, success!

Here’s an example of the complete treatment procedure: (1) flakes before treatment; (2) facing applied; (3) application of 50% IMS and gelatin, followed by heat activation; (4) after setting, the facing is removed with a warm, wet swab; (5) tweezers are used to pull the facing gently off; (6) the area after treatment, success!

Once we were confident that this method worked, the angel in its packaging was set on the operating table and the areas identified as most fragile were faced and treated. There definitely was a ‘surgical theatre feel’ to all this, with two conservators each working on each side of the box, passing around spatulae, brushes and adhesive solutions. Everyone fell promptly into their roles and the rhythm of work got going.

Here, Claire and Dae-Young are stabilising the angel, before its removal from its temporary packaging.

Here, Claire and Dae-Young are stabilising the angel, before its removal from its temporary packaging.

The “operating table” so to speak, with different parts of the treatment taking place at the same time.

The “operating table” so to speak, with different parts of the treatment taking place at the same time.

Letty and Young heat activating the Klucel G and gelatin using heated spatulae.

Letty and Young heat activating the Klucel G and gelatin using heated spatulae.

After the first day, the angel was lifted out of its box successfully without any severe loss of gilding. This allowed us to access more surface area on the angel and so the work intensified during the next two consecutive days, as you have seen already in some of the photos. Facings were applied, flakes were relayed and facings taken off. The most challenging areas were the face, wings, chest and feet on the angel due to the undulating surfaces and level of decorative carving. At times, some flakes were broken or damaged during treatment which was heart-wrenching, however, the solution to this was very straightforward: document it and then repair it.

Some stunning work achieved by Claire on the face of the angel.

Some stunning work achieved by Claire on the face of the angel.

Similar successes on the left wing – clearing the facing was particularly tricky here, as it tended to catch on the decorative carvings, lots of care and caution were thus necessary to achieve these results!

Similar successes on the left wing – clearing the facing was particularly tricky here, as it tended to catch on the decorative carvings, lots of care and caution were thus necessary to achieve these results!

At the expiry of the available time, the angel was miraculously looking in much better shape than before, and in turn was also much more stable! Indeed, the success of the treatment allowed us to move the angle from a lying, horizontal position to a standing, vertical one. Advantageously, this then permitted an improved packaging solution to be implemented whilst more work was carried out at a later stage.

The angel after three days solid work – and finally standing whole!

The angel after three days solid work – and finally standing whole!

Yes, despite the advances made at this stage, the treatment was not yet over and further relaying of gilding and paint was necessary. This was completed in part during another similar session in February. In fact, should you wish to know about this session, we will be more than happy to answer your questions in person at this World Archaeology Day Festival at the UCL Institute of Archaeology, come Saturday the 13th June! There’s an even more exciting part though! We shall be working on the angels this Saturday and you will have the opportunity to see how this work is done in real-time. So don’t miss out on this fantastic opportunity to set your eyes on these angelic beauties, we look forward to seeing you!

WE LOOK FORWARD TO SEEING YOU THIS SATURDAY!

WE LOOK FORWARD TO SEEING YOU THIS SATURDAY!

N.B. All photos by Claire D’Izarny-Gargas & Jan Dariusz Cutajar. Permission to post courtesy of the Norfolk Museums Service.

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Material Spotlight: Agar Gel

Robert Price

I’m just going to come out and say it – gels are pretty amazing.

Jurassic Park (1993)

Jurassic Park (1993)

No, not this kind…

I mean, sure, Jell-O or Jelly is pretty great too, but I’m talking about the gels used in conservation and my new favorite gel – Agar.

If you’ve done some lab work you’ve probably come across Laponite RD (a synthetic clay), Carbopol (a carbomer resin), or Cellulose Ethers like Methyl Cellulose or Sodium Carboxymethyl Cellulose being converted to gels for cleaning techniques involving water, solvents, or other cleaning agents.

Gels are useful because they minimize the total amount of solvent or water needed for a treatment by slowing the rate of evaporation and maintaining good contact with the surfaces targeted for cleaning – this is good for you, the environment and the object. In some circumstances gels can also have a poulticing effect and are capable of absorbing a portion of the materials they solubilize or soften.

Aside from potential chemical interactions, a big consideration with gels is how easily you can remove them once they have worked their magic – a process known as ‘clearance’. With some gels this might be particularly problematic, especially when used on very rough or porous surfaces. Not all gels are the same though and you need to do some research.

But here’s where my new favorite material comes in – enter, Agar gel.

If you look into the literature you might be surprised to see the wide range of materials it has been used to clean, including: wax sculptures, marble, gypsum plaster, ceramics, wood, and textiles. Anecdotal reports from our peers currently undertaking work placements have also noted its growing use within museums, especially for surface cleaning on limestone.

The beauty of the gel is that it’s capable of slowly releasing water in very small amounts, which means that it can be used to remove or soften water-soluble materials without overly saturating a water sensitive surface. Unlike other commonly used gels, the rigid gel formed by Agar is extremely easy to remove in a single piece and leaves no visible residues behind. This minimizes the amount of mechanical action needed to clear the gel. You should be aware, however, that at least one study has identified trace amounts of polysaccharides within cleaned materials analyzed with GC-MS.

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Comparative clearance tests with commonly used gel concentrations on Melinex

Personally, I have found it to be a promising material for softening and removing proteinaceous glues in situations where excessive amounts of water or heat would be problematic for the object being treated – as is the case for bone and wood.

It’s definitely worth experimenting with, even if you don’t currently have a use for it. While purified agarose can be purchased online, food grade Agar is much cheaper and can be purchased from higher end grocery stores. Even some high profile cleaning projects have gone with this cheaper alternative. I’ve been using Clearspring® Agar Flakes.

Try making a 2% w/v gel by adding 2g of agar flakes to 100ml of boiling water and a allowing the solution to cool within a flat container. The resulting sheet can be cut into whatever shapes you need and will keep in the fridge for a week or more depending on the cleanliness of your equipment and how often you open the container.

A square of Agar gel, roughly 3mm thick.

A square of Agar gel, roughly 3mm thick.

Unfortunately, these tidy little sheets only work well on flat surfaces. As an alternative, the semi-cooled solution can also be placed in a plastic syringe and extruded just before gelation occurs, allowing the gel to better conform to complex surfaces. This takes some practice and familiarity with the material but can be very effective.

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Direct application of the gel near its ‘sol-gel’ transition temperature.

Finally, you can also experiment with forming the gel around other materials as I did with natural fiber strings. The string can be repeatedly dipped in and out of the warm solution until a thick coating is formed around the fibers. Strings with looser twists and greater surface area work best. This gives the gel a support structure and made handling and removal even easier. Possible applications could be for disassembling narrow joins or lying over curvilinear shapes.

Non-dyed, natural fiber strings used as ‘scaffolding’ for the gel

Non-dyed, natural fiber strings used as ‘scaffolding’ for the gel

Hopefully this has been helpful and got you excited about exploring Agar gel further. It might be a good alternative to consider the next time you have to remove proteinaceous glue from a fragile or water sensitive surface.

 

 

The Polishing Rush

Anna Funke

The last weeks of term are always a challenge in getting everything finished, but this term one task in particular – polishing SEM samples – took its toll on everybody’s patience.

The SEM (Scanning Electron Microscope) is a powerful analytical tool for our work. However, the sample preparation process is rather tedious. Just a quick reminder, a scanning electron microscope uses an electron beam (rather than light with standard optical microscopy) to produce images up to 500,000 x magnification.

Although there are several different methods for preparing these samples, our technique involved mounting our samples in resin (Clear Casting Resin POLYLITE 32032-00 from Alex Tiranti Ltd., to be specific), using ice-cube trays as moulds.

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Resin-cast samples of glass beads prepared by Emily Williams.

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An SEM image of the above sample, as prepared by Emily Williams. The glass appears grey in this image, and the swirls show that the glass was poorly mixed. The white specks in the sample are unmelted metal colorants in the glass.

Once cast, the resin block has to be prepared and sawn into the correct shape. This often requires some elbow grease and several sacrificial saw blades. The sample is then polished to the smoothest possible surface. This required four grades of abrasive paper, followed by 4 grades of micro mesh that added up to a good 5 hours per sample. One of the challenges is to make sure you are not left with scratches all over your sample.

The polishing work station of Megan Narvey.

The polishing work station of Megan Narvey.

The author and Megan Narvey discovering a significant amount of scratches on their samples.

The author and Megan Narvey discovering a significant amount of scratches on their samples.

At the end this long process you should have a shiny smooth resin surface, and are likely to have repetitive strain disorder. But if, against all odds, you do succeed in preparing a beautifully smooth surface, the images you will get in return for your labour are really quite amazing!

Sample of a cross-section of a painting by Kristen Gillette. Layers 1, 2, and 3 are surface pigments, probably acrylic paints; Layer 4 is a pigment ground layer; Layer 5 is the ground; and Layer 6 is animal skin.

Vanessa Applebaum’s cross section of painted plaster along with elemental maps of the sample.  Explain what can be seen here

Vanessa Applebaum’s cross section of painted plaster along with elemental maps of the sample. The cross section shows the plaster, applied pigment, and a carbonation layer. The elemental maps identify where specific elements are located in the sample. They are, starting from the top and moving left to right: silica, iron, chlorine, calcium, titanium, aluminium, potassium, and sodium.

Discover What is in Your Lab: Unlabelled Blue Pigment

Julie Flynn

As part of an assigned research project in the conservation materials science course, I was given an unknown bright blue crystalline material. The original context of the sample was unknown, but it was assumed that it was a pigment, possibly Egyptian Blue. Visually comparing my sample to a known sample of Egyptian Blue, it was obvious that they were not the same. In order to demonstrate this, I began investigating this unknown blue using various techniques available to me at the Institute of Archaeology at UCL.

The bottle of unknown blue pigment

The bottle of unknown blue pigment

Polarised Light Microscopy (PLM) was the first technique that I used to examine the sample. In this technique a prepared sample is illuminated under magnification with polarised light.

For comparison, here are the PLM images of the unknown sample and the known Egyptian Blue. Out of all the known samples I analysed, Egyptian Blue pigment had the largest grain size. However, as you can see in these two images at the same magnification, the unknown sample still has much larger grains!

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PLM image of the unknown sample

 

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PLM image of Egyptian Blue

The unknown blue has grains at least twice as large as the Egyptian Blue. The other known samples of blue pigments in the lab had even smaller grains – smaller than 10 µm in length.

I was able to carry out elemental analysis using both portable X-Ray Fluorescence (pXRF) and Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS). In pXRF, secondary electrons in a sample are excited by bombarding the sample with high energy x-rays. Each element fluoresces differently, making this a good elemental analysis technique. IN SEM-EDS, an electron beam is scanned over the sample’s surface, and the electrons striking the sample produce signals. These specific signals can identify specific elements. Here are the results for identifying the blue portion of the samples.

Major Elements Found Within Pigments With Two Methods of Elemental Analysis

Pigment SEM XRF in Mining Mode
Unknown Pigment O, Na, Cu Cu
Egyptian Blue O, Cu, Si, Ca Si, Ca, Cu

The elemental composition of the two samples are different therefore, at this point, I believed that the unknown blue was not Egyptian Blue.

Now that I had established that the unknown sample was definitely not Egyptian Blue, I needed to find out what it was. For this, I used Energy Dispersive X-Ray Diffraction (EDXRD) to determine the unknown blue sample’s chemical composition. EDXRD uses X-Rays to reveal information about the crystal structure of the sample, which in turn reveals information about the sample’s chemical composition.

When I analysed the sample using EDXRD, the ICDD (International Centre for Diffraction Data) database of minerals found a very close match to the composition and crystal structure of the unknown blue pigment: sodium copper carbonate (Na2Cu(CO3)2).

 

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EDXRD diffractogram comparing the unknown blue sample to sodium copper carbonate (Na2Cu(CO3)2). This mineral matched closely to the chemical composition of the unknown blue sample. It also matches the results from the prior elemental analyses.

There is a rare mineral of sodium copper carbonate known as Juangodoyite. This mineral was discovered in situ in a Chilean mine in the Atacama Desert in 2003 by Arturo Molina, Iquique. It is formed by the dehydration of chalconatronite, which has the chemical composition of Na2Cu(CO3)2•3H20, and is a corrosion product of bronze. There is no evidence to suggest that this mineral has ever been used as a pigment.

Besides elemental and chemical composition analyses, more evidence that the unknown blue sample is juangodoyite is that they both form in crystals and have a bright ultramarine colour. Evidence against the unknown blue sample being Juangodoyite is that the minerals found in the Atacama Desert were 5 µm in grain size, which is much smaller than the unknown blue sample.

It’s curious to consider how this rare mineral came to UCL in the first place. Its origin at the Institute of Archaeology is shrouded by age, having passed from one professor to another professor many years ago under the name “Egyptian Blue”. It could have come from one of the Institute’s many international expeditions, or from a previous experiment to create a historic type of blue pigment. There are many possibilities – what do you think?

 

Let the Treatment Begin!

Abigail Duckor

Following the research conducted by Claire d’Izarny-Gargas, further examination led to the formation of treatment plans for Angel A and Angel B. As discussed earlier, Angel A was in decidedly better condition, so it was tackled first.

Claire starting the treatment on Angel A

Claire starting the treatment on Angel A, courtesy of Norfolk Museums Service, T1878333.

On the front and the back of the angel were two different types of surfaces. The front was a gilded layer, which was flaking and delaminating. The back featured a painted layer, also undergoing flaking, but not as extensively. The front and the back of Angel A therefore underwent different treatments. This blog post discusses the relaying of the flaking gilded surface. For the front of the angel the main goals were to clean the surface (which was very, very dirty!) and to relay the remaining flakes. An initial gentle clean was done with a cotton wool swab and a solution of 50:50 IMS (industrial methylated spirit) and deionised water. This method was selected after some cleaning tests were carried out in an inconspicuous area.

Cleaning tests on Angel A.

Cleaning tests on Angel A. Courtesy of Norfolk Museums Service, T1878333.

The flakes were then relayed by first saturating the area with the 50:50 IMS/ deionised water solution. Then, using a small brush, a drop of warmed gelatin solution (5% w/v in deionised water) was placed under the flake. Saturating the area first reduced the surface tension and allowed the gelatin to penetrate under the flake.

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The gelatin was dissolved in warm deionised water. It was kept at 60°C in a water bath. Photograph by A. Duckor

After the gelatin cooled a bit (a few minutes), heat was applied to the area with a heated spatula. A piece of silicone-release paper was used between the  spatula and the angel, to prevent damage to the surface from the tackiness of the gelatin. Pressure was gently applied to the flake with the heated spatula, in a ‘rubbing’ motion. The gradual heating softened the gilding and allowed it to be re-shaped onto the surface of the angel. The heat ‘activated’ the gelatin and adhered the flake onto the substrate.

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The heat spatula and brush used in the flake relaying. Photograph by A. Duckor

This method was very successful in relaying the flakes with little breakage. Following re-laying, further cleaning could be done without risking additional damage to the surface.

The left hand of Angel A before and after the flake relaying. Courtesy of Norfolk Museums Service, T1878333.

The bulk of this treatment took place during the summer months of 2014 and allowed for the involvement of both MSc and MA conservation students – a great opportunity to work together and learn from one another!

Erin Murphy using the heat spatula to gently press down a flake and seal it with the gelatin.

Erin Murphy using the heat spatula to gently press down a flake and seal it with the gelatin. Courtesy of Norfolk Museums Service, T1878333.

Rachel Altpeter and Romina Quijano Quinones working together.

Rachel Altpeter and Romina Quijano Quinones working together. Courtesy of Norfolk Museums Service, T1878333.

Yuqi Chock applying gelatin to flaking areas of gilding.

Yuqi Chock applying gelatin to flaking areas of gilding. Courtesy of Norfolk Museums Service, T1878333.

Photographs by A.Duckor and Claire D’Izarny-Gargas.

Work Placements – transitioning from the UCL conservation lab to a professional institution

Veronica Ford

So far in this blog we have seen a lot of stuff from the current inhabitants of the UCL conservation lab. As you know from Megan’s introductory post, the MSc in Conservation for Archaeology and Museums is actually a two year course.

“But what about last years’ lab students? What are they doing?” I hear you cry.

In the second year of the MSc for Conservation for Archaeology and Museums, students are assigned work placements lasting a total of 10 months to give them experience of the reality of the working environment (in other words – it’s a wake up call!).

My placement has been divided between two institutions. Between September and December, I spent time with the preventive conservation team within the Bodleian Libraries. From January onwards, I’ve moved on to the Ashmolean Museum of Art and Archaeology, both institutions located in Oxford.

The past six months have been a massive learning curve!

When people think of conservation they might imagine a lab-coated conservator gluing an object back together.

Something like this. Which sometimes is the case, nevertheless (photo courtesy of Naomi Bergmans).

Something like this. Which sometimes is the case, nevertheless (photo courtesy of Naomi Bergmans).

But in reality the role is far more diverse than that!

The two institutions I have been hosted at have been quite different (though very close to each other geographically). At the Bodleian, I was part of the preventive conservation team, ensuring that objects are kept in good environmental conditions (including temperature, humidity, light exposure, and so on) and that they are well stored and handled in order to minimise damage. I was also involved with the environmental proving of a new library building. This meant consulting with builders, contractors, other conservators, librarians, and curators. It also required a scientific approach to understanding the environmental factors that might adversely affect the storage of library materials. As part of this we implemented a dust monitoring programme in the new library, and carried out research into pest eradication.

The view from my office in the Bodleian wasn't half bad (photo courtesy of Veronica Ford).

The view from my office in the Bodleian wasn’t half bad (photo courtesy of Veronica Ford).

At the Ashmolean, however, I have focused more specifically on interventive conservation (i.e. the active treatment of deteriorated and broken objects). In addition to object treatments, I have been involved in a broad range of museum activities including pest monitoring, condition assessments, loans and exhibition installations.

No complaints about my view from the Ashmolean either (photo courtesy of Veronica Ford).

No complaints about my view from the Ashmolean either (photo courtesy of Veronica Ford).

The two experiences combined have shown me the true breadth and diversity of activities with which conservators are involved. Basically – we need to be involved whenever there is a risk that an object might be/has been damaged. Conservation treatment work needs to be fitted around this, as conservators are often required to jump in and get involved with other museum activities at the last minute. This is in contrast with my experience working in the conservation lab at UCL, where the majority of my time was spent actively working on object treatments.

At UCL, I was encouraged to gain experience with extensive research, complex analysis and challenging treatments. The need to develop hand skills and experience meant I was encouraged to undertake complicated treatments. This contrasts to some degree with my experience at a working institution, where the focus of treatment decision making is defined by the needs of the institution, and where time and resources may be limited.

Two previously restored ceramics with two different approaches (before treatment). Left - that undergoing treatment at the Ashmolean. Right - that treated at UCL (photos courtesy of Veronica Ford).

Two previously restored ceramics with two different approaches (before treatment). Left – that undergoing treatment at the Ashmolean. Right – that treated at UCL, Copyright UCL Institute of Archaeology Collections (photos courtesy of Veronica Ford).

This is clear in my approach to two archaeological ceramics both with broken Plaster of Paris fills, one of which I treated at UCL and one of which I am currently treating at the Ashmolean. My approach at UCL was thorough: I removed the old adhesive from the ceramic and reconstructed it from the beginning with conservation adhesive (Paraloid B72*), creating structural fills only where necessary. At the Ashmolean, I have decided to replace and repaint the broken fills, avoiding a complete deconstruction. This conserves time and resources and offers the least interventive approach, whilst still stabilising the object and fulfilling treatment goals.

I have learnt that it is necessary, in a professional context, to be pragmatic and realistic. This however need not be an obstacle to more in-depth research projects. The Ashmolean is always looking for new ways of researching and analysing the collection and recently received funding to carry out analysis on 500 objects belonging to the recently acquired Wellby collection.

It is hard to be glamorous when you work on a building site: moving special collection material into the new library building (photos courtesy of Veronica Ford and Naomi Bergmans).

It is hard to be glamorous when you work on a building site: moving special collection material into the new library building (photos courtesy of Veronica Ford and Naomi Bergmans).

At times conservation work can seem unglamorous or routine. But such activities are absolutely vital for the preservation of collections. For instance, an important preventive conservation activity is condition checking new acquisitions, to ensure that they are not actively deteriorating and can be safely stored with other collection material. This can sometimes result in rather difficult and less pleasant working conditions.

Spores for thought: checking new acquisitions for mould at the Bodleian (photo courtesy of Veronica Ford).

Spores for thought: checking new acquisitions for mould at the Bodleian (photo courtesy of Veronica Ford).

Conservation is often a controversial activity and it can be hard to balance established conservation approaches with increasing pressure on heritage institutions to maximise access to, and use of, collections. I am finding that essential conservation skills include the ability to negotiate with others, to communicate conservation needs clearly and accurately, and also to show willingness to be flexible and compromise where necessary. Although, in theory, this is clear to many conservators in training, the lesson cannot truly be learnt without direct experience.

* An ethyl methacrylate copolymer. Just in case you are wondering.

Acknowledgements: Thanks to my lovely work placement hosts at the Bodleian and Ashmolean and to Naomi Bergmans for some of the photographs.

A Glass Puzzle from Tell Fara

Emily Williams

Image Of The Glass Sherds Before Treatment. Copyright UCL Institute of Archaeology Collections

When I first came across the box full of archaeological glass fragments in the conservation lab, it raised a strong sense of curiosity and concern – I did not want the box of bits to go back to the collections store in the same condition, and without knowing what this golden iridescent glass used to be. The box contained 19 fragments, too few to make up a whole vessel, so early on, I had to abandon any idea of being able to reconstruct a complete object. After many hours of research, and what felt like the longest, most complicated puzzle I had ever done, I was however able to piece enough fragments together to infer the shape of a bottle.

Reconstructing the bottle. Copyright UCL Institute of Archaeology Collections

Once I had identified that the fragments formed a bottle, I attempted to reconstruct it. The glass was however too fragile to handle without the surface layers becoming detached. Before I could do anything else, I needed to consolidate the surface. This was done using very low percentage of Paraloid B 72 in acetone. I carefully applied this solution so that the polymer went under the delaminating flakes in order to reattach them to the underlying glass.

Making the Fill using Japanese Tissue. Copyright UCL Institute of Archaeology Collections

After I consolidated the surface, I put the fragments together with a more concentrated solution of Paraloid B 72. Stronger epoxy adhesives are often used to reconstruct glass objects in collections (like Hxtal NYL-1), but was not used with this archaeological object as the treatment would not have been so easily reversible. The potential for conservators in the future to retreat our conserved objects is always considered when we make decisions about our treatments now. I then used watercolour paints to colour Japanese tissue a very pale blue/green and sandy yellow in order to match the colour of the glass underneath the layers of corrosion. The tissues were shaped by hand, cut to size, and then attached as a support to the reassembled glass fragments.

The Reconstructed Base of the Bottle. Copyright UCL Institute of Archaeology Collections

For the upper section of the bottle, I experimented using a light bulb as a base to create my rounded fill. Shaping Japanese tissue so that it remains curved can be quite tricky. My lab partner Robert suggested I coat the light bulb in a thin layer of silicone to create a barrier between the two, this allowed me to remove the tissue from the light bulb surface once it had dried. I used T40 Silicone Rubber from Tiranti, which is a two part thixotropic mixture with a curing time of approximately 30 minutes.

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Using the Silicone covered light bulb as a mould for a Fill

One complicated aspect of the reconstruction was having to figure out how to reconstruct a closed vessel when the only opening was through the very small and narrow neck of the bottle. Once I had all my tissue supports in place, I inserted a bent wooden stick with a flattened silicone tip so I could reactivate the adhesive with acetone and use the silicone tip to press the tissue onto the glass from inside the bottle.

Glass Irridescence On The Inside Of The Bottle. Copyright UCL Institute of Archaeology Collections

Finally, the glass bottle reconstruction is now complete! The object will be returned to the UCL Institute of Archaeology’s Palestine-Petrie Collection, and is now readily available for teaching and research.

Image of the Bottle After Treatment. Copyright UCL Institute of Archaeology Collections

The Writing on the Sherd

Megan Narvey

One of the objects I am in charge of this year is this small ceramic pot, belonging to the Petrie Museum of Egyptian Archaeology:

Before Treatment photo of the archaeological ceramic in question. Courtesy of Petrie Museum of Egyptian Archaeology, UC65224

Before treatment photo of the archaeological ceramic in question. Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC65224

One of the interesting things about this object is that it was excavated by a rather famous early archaeologist, Sir William Matthew Flinders Petrie. Petrie is famous in archaeological circles as a pioneer of modern archaeology, implementing methodical techniques and caring about the small details.

Portrait of Sir William Matthew Flinders Petrie, 1903

Portrait of Sir William Matthew Flinders Petrie, 1903

Petrie’s legacy was visible right on the inner wall of one of the large sherds on my pot – the blue pencil markings were identified as belonging to him. Unfortunately, they are very difficult to read.

This blue pencil writing belongs to Flinders Petrie. Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC

This blue pencil writing belongs to Flinders Petrie. Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC65224

The pot had undergone a previous treatment some time in the past that had now failed, leaving several sherds detached, as you can see in the first photograph above. Additionally, the pot had survived not one, but two historic fires! This had left a thick layer of soot on the object, which you can see below. In order to remove it, I had to spend a lot of time testing different cleaning methods and looking at the surface of the ceramic very closely.

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Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC65224

There was an exciting and unexpected consequence of spending a lot of time cleaning the sherds –  I saw strange shimmery lines underneath engrained soot on one of the fragments, almost invisible to the naked eye. In order to figure out what I was seeing, I looked at the fragment with an infrared (IR) Dino-Lite, a handheld digital microscope. The infrared rays, with a longer wavelength than visible light, allowed me to not only see more clearly, but take close up images of what was hiding under the soot.

Here is an image of the sherd under normal light:

An image of the fragment with the hidden writing. Can you spot it? Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC65224

An image of the fragment with the hidden writing. Can you spot it? Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC65224

In contrast, here is what was captured with the IR Dino-Lite:

The IR Dino-Lite images of the hidden writing.

The IR Dino-Lite images of the hidden writing.

I also annotated the photograph on Powerpoint so that the writing was bright red, making it easier to read:

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Whatever is written here is very similar to and in much better condition than the original and much more obvious writing, even under the same conditions!

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I now need to help to identify what is written. What do you think? Can you decipher what Petrie has written?

 

Characterization of Gilding Layers on Gilded Wooden Sculpture

Claire d’Izarny-Gargas

Back to the stunning pair of Angels from Blo Norton Hall Chapel – see the first post in the series here.

Angel A (right), and B (left). Courtesy of

Angel A (right), and B (left). Courtesy of Norfolk Museums Service, T1878333.

Before proposing a suitable conservation treatment for the Angels, we needed to better understand how they had been made and the causes of the dramatic flaking of the gilded layers on both Angels.

An initial examination showed that they were covered by several layers of gilding and that the detachment of the surface appeared to be at the same layer on each of the Angels, revealing the mordant of an older gilding layer. The high degree of damage and the shiny/waxy appearance of the uncovered mordant suggested that some change had occurred between the two gilded layers, causing the detachment of the outer gilded layer. It also appeared that the mordant was composed of wax, rather than animal glue, which is a more commonly used gilding technique. Further analysis could help to confirm this, and would give a better understanding of the composition of the successive layers added to the surface, and an idea of the type of gold used – was it pure gold leaf or an alloy?

Detail showing two gilded layers on the arm of Angel A. Courtesy of

Detail showing two gilded layers on the arm of Angel A. Courtesy of Norfolk Museums Service, T1878333.

Detail showing the yellow 'waxy' mordant on the dress of Angel A. Courtesy of

Detail showing the yellow ‘waxy’ mordant on the dress of Angel A. Courtesy of Norfolk Museums Service, T1878333.

Angel A was investigated by using a combination of techniques, such as micro-chemical spot testing of samples (flakes which had fallen off the statue), Fourier transform infrared (FTIR) spectroscopy, observation under ultra violet (UV) fluorescent light, thermo-microscopy and analytical studies of two cross-sections under the polarised light microscope (PLM) and scanning electron microscopy with energy dispersive x-ray spectrometry (SEM-EDS). Each of these analytical techniques enables us to characterise the materiality of the object with different degrees of accuracy. Correlating the results of the different analytical techniques would help us determine how the Angels had been made.

In this post we will talk specifically about the polarised light microscope (PLM) and the scanning electron microscopy with energy dispersive x-ray spectrometry (SEM-EDS), which are two amazing techniques that, when combined, allow us to get accurate results.

Two samples, taken from different areas of the statue, were prepared in cross-section. The cross-sections were first embedded in a resin and observed under a polarised light microscope.

Two samples of the gilded layers taken from Angel A were embedded in a resin to realize a cross section which will then be observed under the PLM and the SEM-EDS.

Two samples of the gilded layers taken from Angel A were embedded in a resin to realise a cross section, which will then be observed under the PLM and the SEM-EDS.

The PLM gives precise information about the thickness and the number of layers present in the polychrome surface. Moreover, it is possible to identify the number of gilding layers and so to give the number of gilding campaigns carried out on the statue. The use of the SEM means that the morphology of each layer can be studied under higher magnification than with PLM. Also, the EDS can provide an elemental analysis of the sample and therefore identify and precisely locate the inorganic elements present in each layer.

PLM photo showing the layering of the successive layers of gilding. Right: SEM photos, summary of the elements found and interpretation

PLM photo showing the layering of the successive layers of gilding. Right: SEM photos, summary of the elements found and interpretation

The investigation revealed the presence of three gilding layers, each composed of five distinctive layers. The gold leaf layer was made of gold alloy of copper and silver. The fillers were made of calcium carbonate, which was occasionally found mixed with clay. Furthermore, the presence of wax in the two mordant gilding was confirmed, mixed with an unknown component. Finally, the use of white lead pigment was identified alongside iron oxide. The difficulty of adhering gold leaf to a wax surface, combined with fluctuating environmental conditions over long periods of time could have been the reason for the extensive detachment at this level.

Inpainting Decision-Making: An Introduction

Vanessa Applebaum

It’s Fashion Week in London and to celebrate the array of styles and colours I’ve seen walking through the streets, I’ve decided to speak about the nuances of colour matching when one inpaints a decorative or archaeological ceramic.*

As we saw in Emma’s post from last week, repairing a ceramic often requires the application of a fill to replace gaps or spaces, which can both recreate the object’s original form and provide it with structural support. Inpainting the filled area frequently provides it with camouflage, to avoid bringing unnecessary attention and focus to this recent addition.

One aspect of conservation that I find particularly tricky is the lack of a singular, finite answer when it comes to treatment questions. Sometimes, the correct way to proceed for one object is a completely inappropriate method for how you should handle another. An example of this is the difference between inpainting the fill of a decorative ceramic object vs. an archaeological one. Since there is no set criteria for choosing a treatment based upon object material alone, the important thing to keep in mind is the item’s context and its significance to the stakeholders to which it is connected. This will play a key role in any conservation decisions made in the future.

In year one of the MSc programme we are given nine objects of varying origin to conserve, each composed of a different material. The first two we received were ceramic—both high and low fired. Similar to Sarah’s, my high fired ceramic was a blue and white transfer print bowl from the latter half of the 20th century. It used to look like this:

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Object no. 9211 before treatment. Courtesy of Liz Pye.

According to the owner, the main objective of the conservation treatment was to return it to its original decorative function. Since the goal was to regain the aesthetic of the originally manufactured object, it would be important to colour match the fill as close to the colour of the ceramic body as possible.

After reconstructing and filling the bowl, I thought inpainting it would be the easy part. After all, the bowl was white wasn’t it…? Not so much. As it turns out, recreating a ‘white’ colour is not as simple as you’d think, and in the case of my ceramic bowl, its ‘white’ body was actually a combination of five pigments.

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The five pigments I combined to mimic the ‘white’ of my high fired ceramic

After many trials and mixing combinations, I was able to come up with the correct colour to match the bowl, as you can see below:

Colour match success!

Colour match success! Courtesy of Liz Pye.

Once I mixed the appropriate colour, it was applied to the fills and allowed to dry. Upon completion, the bowl looked like this:

Object no. 9211 after treatment

Object no. 9211 after treatment. Courtesy of Liz Pye.

The fills and inpainting can be considered successful because of their close similarity to the object’s existing colour. Because of this, I was feeling confident in my abilities to match and was quite happy that I’d cracked the correct method of dealing with ceramic fills…until I realized that was completely different to the considerations that had to be given to the inpainting of my low fired ceramic, which were two sherds** from a pinch pot dated between 3300 – 2700 BCE, spanning Predynastic and Protodynastic Egypt.

Before they were joined, the sherds looked like this:

 Object no. UC 66105 before treatment. Courtesy of UCL, Petrie Museum of Egyptian Archaeology.

Object no. UC 66105 before treatment. Courtesy of UCL, Petrie Museum of Egyptian Archaeology.

Unlike the high fired ceramic, the objective for this treatment was to stabilize the object for future handling and use in a university research collection. The sherds needed to be reattached, with fills added for structural support. Like the bowl, these fills needed to be inpainted so that the repair wasn’t distracting when viewing the object; however, unlike the bowl, the colour of the fills needed to be distinct from the ceramic body. This is because the object will be studied and viewed in the context of its place in an archaeology collection, and so there should be no question as to what is newly added and what is original to the manufacture and use of the object. This presented the challenge of coming up with a colour that would simultaneously look similar yet different to the original.

In the end, the following effect was created on the area of fill through paint layering and surface finishing:

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(Courtesy of UCL, Petrie Museum of Egyptian Archaeology, UC 66105.)

Both of these inpainting jobs were considered successful because they weren’t judged by the same set of criteria. Instead, conservation methods were created from the context clues and significances that were applied to them. For someone who used to study scientific and mathematical concepts  that purported to have ‘right’ and ‘wrong’ answers, this was a departure from my comfort zone. That being said, the problem solving that conservation encourages and the creativity that I now enjoy were things that I quickly learned to appreciate. …And as an entirely added bonus, I can now say that I understand colour matching as well as those down at London Fashion Week.

*Ceramic – a material composed of inorganic compounds of varying compositions, which can be high fired fired (porcelain) or low fired (terracotta flower pot).

**Before anyone thinks this is a typo and that I meant to say ‘shard,’ ‘sherd’ is a term often used to describe archaeological ceramic fragments.