When people think of Celtic culture, sometimes their mind goes straight to a man wearing a patterned kilt playing a matching set of fabric bagpipes. It’s a vivid cultural image, in part thanks to to the rich fabric that man is wearing. The kilt of this imaginary man is tartan, a pattern of interlocking lines of varying width that run horizontal and vertical across the fabric. In Scotland, the Tartans have large cultural significance. The oldest known tartan item in Scotland dates back to the third or fourth century. In early times, tartan would have been homespun with wool. The...