To create the paintings, silk was stretched onto a wood frame with wheat starch paste and sized to prepare for painting. The frame was often placed flat on the ground - the artist kneels on a "bridge" to reach areas. The paints consist of mineral pigments in an animal glue binder.
The traditional treatment for such a work would be to line the painting with paper and dry it on a karibari board, as protein (silk) deteriorates quickly without cellulosic support. However, research uncovered the fact that "Iris" was in its original exhibition format - this format is a rare snapshot of the time, and the curator wanted to retain the stretcher and the translucent appearance of the painting.
"Iris" was exposed and tearing at stress points, and had extensive foxing spots. It was necessary to control moisture during the treatment, so gels were used to reduce foxing:
Agarose 5% with EDTA, with sodium citrate - slight tidelines.
Gellan 5% with EDTA and sodium citrate - calcium was not used in preparing the gellan to allow use of the chelator, but the chelator was ineffective.
Gel was cut into dots with a biopsy punch. The dots were placed on foxing spots and left for 1.5 hours until dry, then removed dry - this left no tidelines. Weighting the dots caused tidelines through too much pressure. This treatment for the foxing took 3 weeks total of placing the dots, changing the dots 3 to 5 times daily.
Paper was tested as a potential lining, but it was decided to use a fabric lining. Crepeline silk organdy was chosen, with an adhesive of Lascaux 360 HV : Lascaux 498 HV in a 3:2 ratio, 15% aqueous solution.
Silk was stretched onto a wooden frame with wheat starch paste and placed face down on silicone paper. Lascaux solution was brushed on evenly using a fan brush to avoid gloss.
A Mylar "key" was created, to show where points of adhesion were chosen outside of the painted areas of the iris. A tacking iron was then used to attach the Lascaux/crepeline lining at these points.
This was an interesting presentation both historically as it explained the background of an unusual painting made at a transitional time in Japanese art, and in a practical sense as it demonstrated the use of gels and modern adhesives to help solve the problem of retaining the painting's vulnerable but historically important format.
Julie Niven, Archives Conservator
Mills Memorial Library, McMaster University, Hamilton, Ontario