The bark of Rhaphiolepis umbellata Makino has been used to produce the characteristic black color of so-called Oshima Tsumugi, Examination of dyeing properties for the hot water extracts from leaves as well as bark were carried out. Furthermore, both extracts were devided into two fractions by their molecular weights through dialysis for 24 hours. Each fraction was compared for their dyeing properties on the basis of organic matter weight under the modified Oshima dyeing method. The extracts from leaves dyed more poorly than those from bark at the same concentration of organic matter, but at the same concentration of tannin, both extracts dyed fairly well. Besides, inner dialysate tends to dye better than the outer. These results indicate the importance of high molecular weight fractions including tannin for dyeing properties. The linear relationship was observed between the weight increase of silk fabrics and luminosity.
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