Student Conservator sheds new light on Silver Studio designs

Arantza Dobbels (MA Paper Conservation, UAL) used scientific analysis to help her conserve eight Silver Studio designs.

Arantza Dobbels, (MA Conservation, Camberwell College of Arts) conserved eight original Silver Studio designs on tracing paper as part of her MA Final Project.  Her work built on MoDA’s existing interest in tracing paper as a material. She was able to shed new light on some of the working practices of the Studio through close analysis of the material evidence.

Here, Arantza looks at the analytical methods used by paper conservators to show how they can inform us about artistic process as well as guide conservation treatments. Close observation and analysis lead to some interesting discoveries. These helped Arantza to know more about the objects, and also to propose some theories about practices within the Silver Studio.

‘As a conservator who truly values informed decision-making, I believe that knowing as much as possible about an object can help to inform and improve my treatments’.


Silver Studio designs on tracing paper

The designs I worked on were a mixture of watercolour, gouache and pencil paintings and drawings on transparent paper (also known as ‘tracing paper’).

An exciting aspect of this project for me was the range of transparent papers. Historic transparent papers are known for their brittleness and fragility. It is not uncommon to find these papers in a poor and unsalvageable state, split into hundreds of pieces.

Conservators are always looking for new ways in which these fragile substrates can be better preserved.  My interest stemmed from research into the manufacturing of transparent papers that I had already been carrying out at The National Archives (TNA) with Dr Helen Wilson.

Using Specialist Techniques

I decided to apply the specialist analytical techniques that I had been using at TNA in this project to support any treatment decisions. The main aim of any treatments would be to stabilise the designs, to stop further loss and slow down any deterioration.

The project began with a thorough investigation of the methods and materials used as well as an assessment of the damage sustained by each item. I used a series of instruments and techniques: transmitted and raking light to learn about the surface characteristics of the paper, compound microscopes, and UV light to learn about the paper fibres and analyse the condition of the media.

FTIR (Fourier Transform Infrared Spectroscopy) was used to analyse the composition of materials.

Transparent papers

Transparent papers were historically made using three distinct methods:

  • over-beating of the paper pulp;
  • impregnation of the paper with a transparentising oil or resin;
  • and chemically, through sulphurisation of the fibres.

The use of a combination of these methods was very common, and different methods were popular across different time periods. I wanted to find out which methods were used to make the transparent papers in the Silver Studio Collection.

As a first step I documented the colour of the transparent papers, as colour could be an indicator of deterioration.  I also studied the surface of the papers and the fibres under high magnification. This would help me to determine whether a transparent paper had been created through the over-beating of the paper pulp. I used UV light to record the fluorescence of the paper, since different oils and resins shine in different colours. Lastly I used Fourier Transform Infrared Spectroscopy (FTIR) to non-destructively analyse the composition of the paper.

Preliminary Conclusions

By comparing all the information I had gathered, I was able to make some preliminary conclusions on what the different manufacturing processes were for the papers.

Three of the designs presented characteristics which concur with those of transparent papers impregnated with drying oils. These oils make the paper brown quickly, so this paper was probably already brown when it arrived at the Silver Studio to be used as drawing material. Over the years, the oils decay and create acidity within the paper, making it extremely brittle.

Two designs seemed to present similarities with transparent papers that had been impregnated with a wax or a resin. These papers were thinner, still highly transparent despite their ageing, and with a particularly gleaming surface that pointed at the notion of a product sitting on the surface. They were also highly brittle, indicating that not just drying oils were the cause of brittleness in cellulose, and they presented particularly negative reactions to water and alcohol solvents, which further informed my treatment.

given that transparent papers made with drying oils were probably brown by the time they reached the studio, while overbeaten or waxed papers were not, the idea of particular papers being chosen for specific jobs is not far-fetched.
The last two designs presented very smooth and compact surfaces and no particularly strong results on the FTIR, indicating overbeating as a production method. Additionally, one of these designs was also very brown and brittle, making  a combination of drying oils and overbeating likely.

It is therefore difficult to say whether the designers at the Silver Studio had a preference for any particular type of transparent paper.  But given that transparent papers made with drying oils were probably brown by the time they reached the Studio, while overbeaten or waxed papers were not, the idea of particular papers being chosen for specific jobs is not far-fetched.  This conclusion is supported by MoDA staff in their observation that dress fabric designs for silks, for example, can be seen to have employed the qualities of transparent papers to mimic the appearance of those more delicate textiles.

Gouache and Gum Arabic: some new discoveries

This beautiful and intricate bird design suffered from a large tear and risked losing a corner. The media resembled gouache and watercolour, and under magnification the surface characteristics corroborated this initial observation. Unexpectedly, a comment on MoDA records for this design read ‘charcoal’ as the media type. This was puzzling as charcoal will appear powdery and sit precariously on the paper surface, while gouache should be held down to the paper by its binder (usually Gum Arabic).

When testing the media during surface cleaning, some pigment particles were easily disturbed by the light tap of a chemical sponge. Pigment was lifting off the painted surface as if it was, indeed, chalk or charcoal. I researched relevant literature and dozens of theories, including wet charcoal application techniques and damage to ageing gouache, but none seemed to fit what I was facing.

When I returned to MoDA with the designs, I explained this phenomenon to MoDA’s conservator Emma Shaw. She suggested that perhaps, there had been an inadequate amount of binder for this top layer of pigment to adhere it to paint layers beneath, leading it to come off in a powdery manner.

This intriguing three-layer design had been adhered on the edges to build up the design elements. The adhesion had caused the first layer to tear and made the third layer inaccessible.

       SD4406.  The light colour stains on the edges are the spots where an adhesive had been used to attach the design layers together.

The layers were easily separated in order to carry out surface cleaning and repairs. The adhesive used was very dry and cracked, and through light scraping, removal of some of the residual adhesive was carried out. A small sample of the adhesive was analysed on the FTIR machine, and to my surprise, the result was both confusing and exciting. The adhesive presented 90% similarity to Gum Arabic, a common binder used in the production of watercolour and gouache.

If Silver Studio designers had occasion to mix their own colours, it is very possible that their pigment to binder ratios would vary.
I had never previously heard of Gum Arabic being used as an adhesive, as it is not usually tacky enough to attach things. I was also a bit sceptical of the FTIR results, as I had limited resources to carry out a thorough data comparison, so I kept this piece of information in my notes and shared it with Emma upon my return.

As we pondered my discoveries, a connection between the two occurred to us. The powdery gouache and the Gum Arabic adhesive presented the possibility that Silver Studio designers may sometimes have prepared their own paints at the studio. This would involve having loose pigments and binders such as Gum Arabic present in their work space.

If Silver Studio designers had occasion to mix their own colours, it is very possible that their pigment to binder ratios would vary. This is a possible explanation for the unusual friability of the pigments used on the bird design, as well as the differences in paint thickness and opacity I noticed.

It also explains why Gum Arabic might have been used to adhere the three layers together on the beautiful Chinese flower design. Perhaps the bottle of Gum Arabic was within reach when the designer decided to attach the pieces of paper. Or maybe he accidentally grabbed the bottle of Gum Arabic instead of the usual adhesive!

The eight designs were cleaned, repaired and stabilised through minimal intervention and preservation means. They are now safe from further losses and deterioration.

This project was an incredible learning opportunity for me; it has allowed me to develop my research and conservation skills and is shaping the start of my career in conservation.

Arantza was awarded a Distinction for her MA work, and is now employed in the conservation department at The National Archive. Well done Arantza!

MoDA has hosted many students from the Camberwell Conservation course on work placements over the years.  We are grateful for the contribution they have all made to our shared understanding of methods, materials and techniques within the Silver Studio Collection.

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