| Summary: | 碩士 === 國立臺南藝術大學 === 古物維護研究所 === 97 === Low-oxygen treatment is to lower oxygen concentration to anoxic or a very low level, forming an unfavorable environment for pests to survive, and can also preserve objects by lowering the oxidation rate. Oxygen absorber is one of the ways to achieve such environment, and is suit for handling medium or small size artifacts. It is devided into two groups by compoments, iron base and non iron base. However, iron base oxygen absorber will produce heat and water during oxidation. Following research tries to figure out whether this kind of temperature and humidity changes will cause color changes of silk materials.
In the color fading experiment, 5 different natural dyes, safflower, madder, Cape jasmine, Shoulang yam and indigo, were chose to dye thin silk fabric as samples. Samples are placed in low-oxygen environments, where oxygen level is lower than 0.1%, achieved by 3 kinds of absorbers, Agelong®-G500, Ageless®-ZP202 and RP®-20K, then stored in 3 different lighting environments, dark, ultraviolet absorption film coated fluorescent light, and normal fluorescent light, for 16 days’ and 90 days’ aging. Spectrophotometer is used to measure the color difference before and after aging, then analysis the data with temperature and relative humidity records, also compared the difference between directly contacts and not contact with oxygen absorber, and whether different lighting environments in low oxygen level affects the color of silk or not.
As a result, color changing of silk artifacts in low oxygen environment is depending on lighting conditions, oxygen absorber and dyes. Iron base oxygen absorber, Agelong® and Ageless®, will release water during oxidation and affect objects, thus accelerate color change and reduce the effect of insect mortality. However, changes caused by heat are not very obvious. Organic base oxygen absorber, RP®-K, will absorb water during oxidation and slightly lower relative humidity, compared with the dramatically increase caused by Agelong® and Ageless®. Besides indigo dye samples of no UV lighting and Cape jasmine dye samples of dark, the effect of RP®-K is the least of all conditions. Even so, dyes which are sensitive to light will still fade in no UV lighting and low oxygen environment. In both lighting environment, oxygen absorber directly contact with sample will cause color fading around oxygen absorber, leaving a mark on the object.
The best way of using oxygen absorber is with purged inert gases. It can prolong the low-oxygen maintaining time, and avoid severe changes in temperature and relative humidity. When using oxygen absorber in static system, it would be better to use RP®-K instead of iron based oxygen absorber. Finally, oxygen absorber should never directly contact with object, and should be place into dark during the treatment.
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