Cast in a different mould: a silicone mould for adding leather grain texture to Japanese paper infills

As a part of my final MA project at the Camberwell College of Arts, I did a conservation treatment for the Wimbledon Lawn Tennis Museum in London. The museum had in its possession an album of press cuttings (Figure 1) that had been put together by the French tennis player Jeannette Poncelet. She had been active on the French tennis circuits between 1937 and 1950. Although she never played at the Wimbledon Championships, she was a regular figure in the French games, appearing at Roland Garros and at most of the tournaments in the south of France.

In the years between the wars, the French upper classes spent their winters in the south of the country, travelling to the Mediterranean coast to escape the cold and take advantage of the warmer maritime climate along the French Riviera. Tennis became a very important part of the winter season, and clubs were founded in major towns and cities, including Nice, Cannes, Menton and Monte Carlo. Local French players – including Poncelet – took part in tournaments alongside world-famous tennis stars.

Jeanette Poncelet won the women’s singles at Nice in 1935, 1936 and 1937, and won the women’s doubles six times and the mixed doubles three times by 1938. The war put an end to the winter season, which never really recovered its popularity. Poncelet last played in 1950, and the album in the Wimbledon Museum’s collection covers the years between 1936 and 1948.

Very little has been written about Poncelet’s personal life or her career, so this album fills a significant historical gap and is a highlight of the museum’s collection. It was therefore decided that the album should receive a conservation treatment to as high a standard as possible. When I first saw the album, it was obviously in need of attention from a skilled conservator. Repair was not only aesthetically necessary: the album’s condition meant that it could not be safely handled by researchers or visitors to the museum. It needed stabilisation so that it could be used for research without further irreparable damage being done to it. 

Figure 1 – Front cover of the album. The piece with a yellow flower pattern is a previous repair in French Riviera leather.

The album resembled a scrapbook: it contained silver gelatin photographs and many articles clipped from newspapers and magazines. The contents were attached to acidic sugar paper pages with pressure-sensitive tape, and were separated with glassine paper. Yellowing was visible on the edges of many pages, as well as on the glassine paper and on the photographs. Some of the pages had split along the gutter fold.

The album originally had a post binding style, bound with string through three holes. The boards were covered with printed (imitation) leather. They were worn from frequent use, and a piece of the covering material had been lost from the bottom right corner of the front board. The edges of the boards were split. Depressions were visible on the front and back boards. 

The original post binding structure was broken and had received a previous repair. A piece of French Riviera leather (a decorative imitation leather from France) had been attached to the board to reinforce the spine. A part of it had peeled off from the front, leaving behind adhesive residue. The binding string and original spine were sticky with it. Under the repair, there were more losses in the original covering material. The repair looked unprofessional and was obviously not done by a conservator.

Some of the damaged areas on the cover would have been visible while the album was on display. The museum decided that thorough treatment of the cover was needed. In particular, the losses in the covering material needed to be filled to give the album a better sense of aesthetic wholeness. To ensure that the infills blended in, the raised ‘crocodile skin’ texture of the covering material had to be imitated. I did a great deal of research on different ways of doing this, including 3D printing and using infills of similar-looking leather. Eventually I came across an article from The Book and Paper Gathering by objects conservator Charlotte Ridley. She had used Steramould – a two-part, non-viscous silicone moulding product – to recreate the texture of another leather-like material, Tolex. She then used the silicone cast to transfer the texture to Japanese paper, which she used to infill losses in the material. This method seemed promising.

Charlotte Ridley had coated Japanese paper in a 15% solution of Klucel G in ethanol and pressed it into the cast in layers. When dry, the paper could be peeled off the cast, resulting in a laminated textured paper that was flexible. The advantage of using a solvent-based gel adhesive rather than a water-based one is that the tissue fibres do not swell, which means that they should not pull apart or tear when rubbed over the mould.

Before the treatment began, I experimented with Charlotte’s method, trying out different moulding materials, adhesive concentrations, and ways of toning the infills. I needed a suitably leather-like paper cast that would make the repairs as invisible as possible.

1. Testing different moulding materials

I tested plaster and the Steramould silicone material on a scrap piece of leather and compared their ability to pick up texture (Figure 2). I pressed the materials into the leather and left them to set. Steramould was left to set for approximately 15 minutes before being carefully peeled away. Both materials gave a good impression of the surface. Then I tested both materials on the album cover itself, pressing them into robust areas of the imitation leather. Both materials gave a firm and reusable cast. However, the plaster picked up colour from the album cover and left behind a white residue, and therefore was found unsuitable for use. Steramould did not pick up colour, and left behind only a small amount of oily residue, which did not penetrate into the covering material (Ridley, 2017) and was easily removed with damp cotton wool.

Figure 2 Detailed impressions of the leather surface in Steramould silicone (left) and plaster (right).

2. Testing different adhesive concentrations

Following Charlotte Ridley’s recommendations, I first tested fine Japanese paper immersed in a 15% solution of Klucel G in IMS (industrial-grade denatured ethanol). I used a skewer to press two successive layers of paper into the mould; then I tamped them down using a stencil brush. However, this technique distorted and tore the paper layers. I then tested paper immersed in 10% and 5% Klucel G in ethanol. I found that it was it most effective to apply adhesive in two steps. First, I dipped the paper into 5% Klucel G. The Japanese tissue then set more easily and was less fragile when pressed with the stencil brush. After the tissue was well set in the mould, I applied the stronger 15% solution of Klucel G with a brush. I repeated the same steps for a second layer of tissue.

Figure 3 – Tamping the adhesive-covered tissue down onto the dried Steramould while the Japanese tissue is wet creates a well-defined surface texture.

3. Testing different patterns and degrees of unevenness in the leather

Figure 6 – After drying, the Klucel-soaked tissue mirrors the surface texture of the leather. Strongly textured leather produced the clearest impression.
Figure 7 Detail of the leather grain impression on a moulded tissue sample. When the texture of the leather is less pronounced, it is transferred less clearly to the paper cast.

I wanted to test how different degrees of unevenness in the leather affected the results. I tested scrap red leather with a strong grain and scrap black leather with a more shallow grain, pressing Steramould onto both and then using it to mould Japanese tissue. I found that the silicone worked better on the coarse texture (Figure 6) than on the smoother one (Figure 7). The imitation leather of the album was sufficiently deeply textured, but this technique may not work well for some smoother or more heavily worn leathers.

4. Testing different weights of Japanese tissue

Once I had decided on the method I would adopt, I tested different weights of Japanese tissue. I considered either using a single layer of heavy tissue or laminating two separate layers of thinner tissue. Both methods would produce the thickness that I needed. While it was possible to use thicker tissue with the Steramould cast, the impression in the paper was less clearly defined than with thinner tissue. I therefore decided to use two layers of 9-gsm Japanese spider tissue.

5. Testing different methods of toning the paper

Figure 8 – Textured Japanese tissue being toned with acrylic paints.
Figure 9 – Paper toned before moulding (left) and after moulding (right).

According to Ridley, the textured paper can be toned with acrylic paints to match the surface colour of the artefact after the paper is peeled off the cast. However, when I tried to tone the textured Japanese paper, I found that some of the texture was lost, probably because of the moisture in the paint. I therefore attempted to tone the Japanese tissue before texturing. I toned 9-gsm Japanese spider tissue with acrylic paints, dried it, and then proceeded with applying the adhesive and pressing the tissue into the mould, as described earlier. This worked well.

A note of caution: I found that applying too much Klucel G to pre-toned tissue can create a distracting white shiny layer.

The treatment process

Figure 10 – The Steramould silicone moulding material pressed onto the cover.

I began by pressing the Steramould onto areas of the cover where the covering material was strong enough to bear the necessary pressure, and then left it to set for approximately 15 minutes. Then I peeled it carefully away. The result was a detailed impression on the silicone (Figure 11).

Figure 11 – A Steramould cast of the surface texture.
Figure 12 – Two layers of toned Japanese tissue were laminated together.

I used two layers of adhesive-coated 9-gsm Japanese spider tissue. First, I toned the tissue using Mars black and Payne’s grey acrylic paints to match the colour of the album cover. Then each layer was coated in adhesive, first in 5% Klucel G, and then in 15%. Once the 5% solution had been applied to the Japanese tissue, I pressed each layer, still damp, into the silicone cast with a skewer. Then I applied the 15% Klucel G with a paintbrush and set the texture with a stencil brush. This was repeated for the second layer of tissue. Once the laminated tissue was dry, I peeled it away from the silicone to reveal a detailed cast of the surface of the album.

Small sections of this textured paper were trimmed to shape and then affixed to the damaged areas of the cover using a mixture of Japanese wheat starch paste and EVA (50:50). I used my finger to press the edges where the leather and Japanese tissue met, and then I pressed the edge area with a weight. I probed the Japanese tissue gently with a bone folder to make sure it had adhered to the cover, and left it to dry. The texture of the infills looked less pronounced when the paper was damp from the adhesive, but once dry, it matched the original leather quite closely.

Overall, the conservation work on the album was successful: after treatment, the album was strong enough to be handled and used by researchers and visitors to the museum – which had been one of the primary goals. The small infills with matching texture gave a sense of aesthetic balance to the cover.

This project taught me a great deal. Besides working on the infills, I needed to use leather preservation, bookbinding and photographic conservation materials with which I was unfamiliar. I realised that I will continue to face unfamiliar materials and processes until I become more experienced in conservation. However, by researching these unfamiliar materials, I learned about them and tested multiple treatment options. I made sure that the album received the best treatment I could offer.

Figure 13 – Detail of the front cover before conservation treatment.
Figure 14 – Detail of the front cover after conservation treatment, showing the textured infill.
Figure 15 – Front cover after treatment.
Figure 16 – Tools for the conservation treatment.

Bibliography

  1. Ridley, C. (2017). Conserving with Japanese tissue: beyond books and paper, Part 1. [online] The Book & Paper Gathering. Available at: https://thebookandpapergathering.org/2017/04/06/conserving-with-japanese-tissue-beyond-books-and-paper-part-1/ [Accessed 10 May 2019]
  2. Pataki, A. (2009). Remoistenable tissue preparation and its practical aspects. Restaurator 30(1–2) pp.51–69. Available at: https://www.researchgate.net/publication/249945229_Remoistenable_Tissue_Preparation_and _its_ Practical _Aspects [Accessed 13 May 2019]
  3. Conroy, T. (1987). The movement of the book spine. The Book and Paper Annual, Vol.6. Available at: https://cool.conservation-us.org/coolaic/sg/bph/annual/v06/bp06-01.html [Accessed 20 May 2019]
  4. Adamopoulou, A. (2013). Same albums, different treatment approaches: The conservation of two photographic albums from the first modern Olympic Games in Athens. 1987. 7th Topics in Photographic Preservation, Vol 15, pp.337–348
  5. Ficher, J. (2008). Constructing a first impression of Japan: Recreating a photo album of Felice Beato. Available at: https://kb.osu.edu/dspace/handle/1811/32022 [Accessed 20 May 2019]

All images courtesy of Yue Li.

Yue Li is the director of the Conservation Center, Gaofan Photography Museum, China, and a researcher at the China Academy of Art and the Beijing Archive Center. Yue writes, ‘In October 2012, I began to study for a BA in Photojournalism and Documentary Photography at the University of the Arts and later joined the MA in Curating and Collection course, aiming to obtain more knowledge of photographic curation. Having a background in photography and curating, I developed a strong interest in photographic conservation. I finished the MA conservation course at Camberwell College of Arts in 2019. By combining the results of personal surveys with information from the working visits and a literature review, I also gained a good impression of European approaches to preserving and conserving  photographic collections, and how western photographic curators cope with preservation issues. After I graduated, I went back to China, focusing on Chinese photographic material conservation research. My aim is to take these preservation techniques to China and adapt them to specific Chinese conditions while exploring the techniques of the political photographers in China. So I set up China’s first photographic conservation center in Beijing, and developed strong connections with most of the country’s archives, galleries and museums.  Also, we are planning to create a photo conservation course at the University of China’s Academy of Art.’ 

4 thoughts on “Cast in a different mould: a silicone mould for adding leather grain texture to Japanese paper infills

  1. Hello ! You may be interested in these articles that both explored casting composites before :

    Reidell, Owen, Cast Composites 2010

    Girard, BEVA® 371-based Synthetic Leather
    A Preliminary Investigation on the use of BEVA 371 as a Repair Material for Leather Bindings 2019

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