2014 Volume 22 Pages 133-138
Traditionally, tsumugi has been seen as a secondary product made from inferior cocoons that cannot be used for raw silk. Nowadays, however, tsumugi is considered to be an important type of fabric. Tsumugi is characterized by variation in thickness of its yarn, which is hand-spun from silk floss, but the details of this variation are unknown. Here, we discuss the distribution of tsumugi yarn width, which is considered to be closely related to thickness. To maintain the integrity of the thread, it is impossible for the yarn to be thinner than a certain value. In contrast, there is no upper limit on the thickness of the tsumugi yarn. We used a truncated normal distribution (TND) to describe this asymmetric situation. The convoluted TND and a normal distribution were obtained for practical analysis of the data. Likelihood equations for estimating the distribution parameters were derived as well. The equations were applied to actual tsumugi yarn-width data captured with an image scanner. The convoluted TND summarized the width distribution of tsumugi yarn well.