黄色系天然染料染色布の展示照明による変退色挙動とCIE美術・博物館照明基準による評価

抄録

In 2004, CIE issued a technical report (CIE 157: 2004) entitled "Control of Damage to Museum Objects by Optical Radiation," in which it recommended that materials classified as highly responsive to light (ex. blue wool standard 1 to 3) be exposed for a maximum of 15000 lx·hr/yr. The aim of this report is to validate the new CIE recommendation for natural yellow dyes categorized below the blue scale grade 4. Twenty types of natural yellow dyes on silk were exposed to both white and non-UV fluorescent museum lamps. Color differences were measured at 15000 lx·hr (500 lx at fabric surface x 300 hr) intervals for 10 times, for an accumulated exposure totaling 150000 lx·hr. The results show that non-UV fluorescent museumlamp was 24% more effective in reducing the fading rate compared with white fluorescent lamp. Complying with the new CIE recommended maximum exposure of 15000 lx·hr/yr, the fading rate for most yellow dyes, will be below the noticeable fading degree (ΔE1.6) thus, the CIE recommendation is valid. However, additional dyes should also be classified as "extremely highly responsive." The limiting exposure for Ukon (Turmeric, Cucuma longa L., colorant: curcumin) should be 3500 lx·hr/yr, and Kihada (Amur cork tree, Phellodendron amurencse Rupr., colorant: berberine) and Onion skin (Allium cepa L., colorant: quercetin) should be 8000∼12000 lx·hr/yr. This study demonstrated a need for revised classification of "extremely highly responsive" materials under museum lighting conditions.