The Chester Beatty Library Conservation Department and the Restorient studio in Leiden have been working together closely for years. Andrew Thompson and Sydney Thomson at Restorient have conserved some of the collection’s most important Japanese scrolls and have been extremely generous in sharing some of their expertise with us. Thanks to them we discovered and have adopted the use of yasha, a traditional Japanese dye.
Yasha is the natural yellow-brown dye extracted from cones of the alder tree (Alnus japonica) and it has been used in Japan since the 8th century. In Japanese mounting studios, yasha is still used to dye the lining papers of hanging scrolls and hand scrolls. The light brown colour obtained from the dye helps to soften the white tone of the paper and silk used for linings and repairs.
Through centuries of practical application, the traditional use of yasha has proven its stability and durability which makes it highly suitable for conservation. Scientific studies confirm that papers dyed with yasha remain pH neutral or slightly alkaline, and retain their brightness and colour on ageing. Most plant dyes are light sensitive but yasha is lightfast, a quality which ensures its continued use.
Like many features of the traditional Japanese conservation studio, yasha is now readily available to Western conservators. With a growing interest in adapting conservation techniques imported from East Asia and Japan, the use of alder cones has become a known technique for dyeing paper when working on Japanese or Chinese Art objects.
The preparation of the dye and its application is straightforward.
- Cover the bottom of a pot with alder cones and submerge them in water.
- Simmer for about 2 hours until the colour intensifies in tone.
- Once boiled, leave the dye to cool.
- Strain through a silkscreen or muslin cloth to remove impurities. The dye is now ready to use.
- Cut a number of Japanese paper sheets of the same size.
- Pour the prepared dye into a shallow dish and apply directly to the rougher side of the paper with a large brush on a flat, non-porous surface.
- The brush strokes should be light and must follow the grain direction of the paper to avoid stretching the fibres. Each sheet is dyed individually; the dye is brushed on evenly and the surface of the sheet completely covered.
- The next sheet is laid on top of the last, staggered by 5mm. Repeat the process to ensure the dye is evenly applied to each piece of paper.
- When all the sheets are dyed, lay the stack on felt for 30 minutes to allow the water to begin to evaporate.
- After this short drying period the sheets are stronger and can be separated and left to dry fully on felt.
- Rinse the dried sheets in cold water for no more than a few seconds as the dye is still fugitive and can be removed in water.
- Prepare a bath of water and Potassium Hydroxide (Potash). When the water reaches pH 7.1 rinse each sheet separately in the prepared bath to fix the dye onto the paper.
- Dry the sheets on felt before a final rinse in plain water to remove any excess lye (Potash).
- When dry, the sheets are ready to use.
The process of layering the paper in a stack while applying the dye to each sheet of paper, creates a progressive darkening of tones throughout the stack from a light cream to a yellow-brown tone. The first sheet of paper to be dyed will be darkest in colour as the dye penetrates through the stack when subsequent sheets are dyed. The last sheet to be dyed when it is placed on top of the stack will be the lightest in colour, receiving only a single application of the dye.
As the dye is applied, it penetrates into the paper colouring the fibres internally. This is a major advantage when using this paper for repair as the water cut edge is the same colour as the toned surface. Unlike watercolour or acrylic paint solutions, where the application can leave visible brush strokes and tends not to fully penetrate the paper, yasha tones each sheet evenly, regardless of the size of the piece of paper.
The gradation of colour obtained through the layering application technique is also extremely helpful to the conservator as it quickly produces a large quantity of paper dyed with various shades of a similar tone. The repair paper can then be used selectively to match the colour of a single sheet or for the repair of a full volume. The tones obtained from yasha are even and saturated, yet the paper remains soft and flexible and does not stiffen on drying. After fixing the dye no colour shift has been observed when repairs were applied.
The selection of different varieties of alder cones (both Japanese and European) and the preparation method described will achieve further useful colour variations and help the conservator to produce a large array of toned repair papers that can be kept on hand for use as necessary.
The adoption of the Japanese dye yasha to tone repair papers at the Chester Beatty Library has been a success and we cannot recommend it warmly enough to colleagues. It is a wonderful method for dyeing paper and this readily available material certainly deserves to find its way into every conservation studio.
Julia Poirier, Book and Paper conservator
The Library is very grateful to Andrew and Sydney at Restorient for first introducing us to this versatile dyestuff when Julia undertook a short placement with them in 2013.
This work was first presented as a poster, ‘Yasha – Adapting a Traditional Japanese Paper Dyeing Technique to the Conservation of Parchment and Islamic Paper’ at the IADA conference ‘From Generation to Generation – Sharing Knowledge, Connecting People’ in Oslo, Norway 3-5 May 2017.