This dynamic and thorough talk focused on the Dirghagama Sutra, a ten-leaf accordion format Korean Buddhist sutra dating from the 14th century, treated by the authors in the Asian Conservation Lab at the MFA Boston. Often produced by the ruling classes as a form of prayer for family members, a sutra typically consists of front and back covers decorated with lotus flowers and other Buddhist symbols, a frontispiece, a main body of text, and a dedication specifying the purpose, donor, and date of the sutra. The support is usually brush- or vat-dyed indigo paper, and the media gold and/or silver pigment. Today many sutra covers have lost their silver pigment and retain only the gold. The sutra’s accordion consists of lined sheets of paper joined together at the folds, with joins typically present at approximately every fifth leaf.
To better understand the history and manufacture of the sutra, the authors examined four other Buddhist sutras from the same time period and consulted with a modern-day sutra artist about his extensive experience studying and copying sutras. They learned that the paper is sized with animal glue, then burnished until it is shiny, smooth, and slightly water-resistant; sheets of paper are then layered and joined together to create the accordion. After the pigment is applied with animal glue, the surface is burnished with a bone folder. To achieve the desired results, climate in the studio must be carefully monitored and controlled.
Upon receipt, the Dirghagama Sutra had many condition issues. The surface was abraded, and showed yellow and white accretions. Portions of the paper layers were lifting and misaligned, and there were losses and previous tape repairs. The structure of the Dirghagama Sutra appeared different from the others the authors had examined, as it did not have readily visible seams in the accordion. After very close examination, they discovered two main segments of different lengths, each constructed of several layers of paper overlapping at the seventh leaf. Before beginning treatment, they diagrammed this structure and drew a condition map documenting the sutra’s many condition issues.
To begin treatment, they surface cleaned the paper with a brush, a vacuum, and erasers. Preliminary stabilization was performed on the tears with 1% methylcellulose gel. The front and back covers were released from the text mechanically with a bamboo spatula. The tape carrier was removed with a heated spatula, and the adhesive reduced with a crepe square and a kneaded eraser. To further reduce the tacky adhesive, which analysis showed was rubber-based, the authors experimented with low-polarity solvents. Though toluene was the most effective, they opted to mix it with acetone to give themselves more control while working and ultimately settled on a 1:2 toluene:acetone solution applied over a suction platen.
To fully stabilize the sutra, it was necessary to disassemble the segments and to add new lining layers. Concerned about dimensional changes that might result from exposure to moisture and drying, the authors made templates to record the original sizes of the paper and used the templates along with controlled applications of moisture to manipulate the sizes of the various pieces and to ensure that the folds would align properly when the object was re-assembled. The templates were also useful in determining the size and placement of the fill for a large loss between the eighth and ninth leaves. Though the various pieces of the sutra reacted to moisture differently, they found that once an overall lining was applied rates of expansion and contraction became more uniform. This, along with the use of templates and the carefully controlled exposure to moisture, were the main factors to which the authors attribute the success of the treatment.