What is the reason that just about every tallit has a series of stripes running vertically down the tallit. Is there a reason or is it just decorative? If decorative, when did this practice begin?
The Aish Rabbi Replies:
The tallit needn't be striped at all, yet in fact most are striped. some are striped blue, some black, some bright white, and some with a multitude of colors. Yet in Jewish law the stripes are insignificant. So why the stripes?
Nobody really knows. Yet this is how it's been done by practically all communities throughout the Diaspora for as long as we know, and so we continue the practice.
In 1960, Yigal Yadin headed an archaeological expedition in the Judean desert of Israel. The purpose was to explore a number of caves known to have been used as a hideout for Jews during the Bar Kokhba revolt against Rome (132-135 CE). One of the fascinating discoveries was a number of Jewish tunics, each with stripes similar to the tallit of today. In Yigal Yadin's book, "Bar-Kokhba" (ch. 7), he writes that this was the Roman style of the times.
It is also possible that the stripes in the Tallit were a sort of substitute for the blue string in the Tzitzit, since the identity of the snail that was to be used for the dye was lost.
To learn more, see "Tztzith – A Thread of Light" by Rabbi Aryeh Kaplan.