Anoxia treatment by various kinds of oxygen scavenger: evaluation of effects on pigments [Original title and text in Japanese]

Anoxia treatment by oxygen scavenger is one of the promising methods for insect eradiction. It is safe to human, non-toxic to environment and very easy to use. However, it is important to evaluate its negative effects on materials: what would be caused by packing with oxygen scavengers. In this report, we tested effects on pigments: malachite, azurite, vermilion, iron oxide red, yellow ochre, red lead, hematite, massicot, white lead and indigo. Four kinds of oxygen scavenger were aplied in the experiments, whose commercial names are: Ageless Z, Ageless G, RP system and RP-K. Oxygen scavengers were applied in both standard amount and excess amount. Each pigment sample was observed for 6 months at 25 degrees C. By application of Ageless G, which evolves Co2, powder of red lead turned dark. Change of red lead powder was very significant in an environment with high relative humidity. PbCO3 was detected in the darkened red lead powder. Massicot powder also turned dark by Ageless G with high relative humidity. In this case also, PbCO3 was detected in the darkened massicot powder. On the other hand, Massicot powder was slightly changed in color by applying excess amount of Ageless Z, which seemed to be a result of increase in relative humidity from Ageless Z. Amount of plumbonacrite formation seemed correlated with the discoloring of massicot powder with excess amount of Ageless Z. Samples of Japanese paper painted with pigments were more resistant to visual change in colors, but samples with massicot were slightly discolored by applying excess amount of Ageless Z and Ageless G. With RP system and RP-K, significant visual changes in colors were not observed in these experiments. However, it is necessary to thoroughly know the chemical ingredients of these reagents when applying them to museum artifacts.