A single batch of dye, together with the yarn colored with it, all of which takes the same shade. Natural dyes are made in small artisanal batches, and when one runs out the replacement cannot be matched exactly, so yarn from different lots differs slightly in tone. In a finished rug the difference shows as the color shifts known as abrash, which is read as a sign of hand dyeing, whereas a perfectly flat, uniform color suggests synthetic dyes and machine making.