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Hi Monika, At the 1995 Biodeterioration of Cultural Property 3 meetings in Bangkok (Proceedings pages 555 to 566), Hiromi Tanimura and Seiji Yamaguchi gave a poster which summarized their work on low temperature treatment of Japanese lacquer. They did their treatments on 14 damaged urushi objects so they could measure changes to cracked pieces, or look for problems on ones with borer holes. They treated bowls, dishes, trays and an inlaid box up to 30 x 30 x 12 cm in dimension, so the pieces were representative of a good range of internal constructions and surface detailing. However they stated there is a wider range of urushi work yet to consider. Ages of the pieces were 150 to 50 years old so they had significant number of natural cycles to react to before treatment. Freezing was to -30C and two cycles were done. No changes were measured by micrometer and visual inspection of the pieces pre- and post-treatment. In general I would expect urushi to behave as other good quality coatings, it has microscopic pores whose significance depends on the processing of the liquid and number of coats. Such good barriers (but not perfect) will resist moisture movement over the short duration of the treatment. The most significant threat would be dimensional change from moisture movement, and that is further controlled by the recommended bagging step. The authors also took the step to wrap each piece in a single layer of paper which added a significant moisture buffer. In comparison, the experience from archeological wet site material as described before is expected. Significant and prolonged exposure to moisture leading to saturation allows dissolution of components, swelling and significant mechanical levering, and probable microbial action at some point, all combining to allow delamination to proceed when the freeze-drying was carried out. Quite a different scenario to the dry and nominally intact samples used by Tanimura and Yamaguchi. Currently in Japan, urushi objects are likely to be treated by CAF (controlled atmosphere fumigation) methods, either low oxygen or CO2. Sincerely, Tom Strang Canadian Conservation Institute | Institut canadien de conservation Senior Conservation Scientist | Scientifique principal en conservation Institut Canadien de Conservation | Canadian Conservation Institute Ottawa, Ontario, Canada, K1A 0M5 [email protected] Téléphone | Telephone 613-998-3721 (extension 239) Télécopieur | Facsimile 613-998-4721 Téléimprimeur (sans frais) 1-888-997-3123 | Teletypewriter (toll-free) 1-888-997-3123 ------------------------------------------------------------- To send an email to the list, send your msg to [email protected] To unsubscribe from this list send an email to [email protected] and in the body put: "unsubscribe pestlist" Any problems email [email protected]
