THE OZONE FADING OF TRADITIONAL JAPANESE COLORANTS.

The colorfastness of several traditional Japanese colorants upon exposure to atmospheric ozone was tested in a chamber exposure experiment. Samples, in the form of colorants applied to paper, dyes on silk cloth, and colorants on a nineteenth- century Japanese woodblock print, were exposed to an atmosphere containing 0·40 parts per million ozone at 22°C and 50% RH, in the absence of light, for 12 weeks. Color differences, calculated from the measured diffuse reflectance spectra, were used to assess the rate and extent of the ozone fading. Of the colorants applied to paper, orpiment was the only inorganic pigment that showed severe color loss after ozone exposure. Several organic colorants on paper also reacted, including the widely used plant colorants ai (indigo) and ukon (turmeric). The woodblock print, produced using the plant-derived colorants beni (safflower), ai (indigo), shiō (gamboge) and aigami (dayflower), showed significant ozone fading only in the blue and green areas, which contain ai. Several of the dyed silk cloths also exhibited some color change in this experiment, suggesting that prolonged exposure to atmospheric ozone could pose a risk to these materials as well. [ABSTRACT FROM AUTHOR]