These very special hand sewing threads are hand dyed in a traditional persimmon tannin. This Japanese technique is over 1000 years old and creates incredibly gorgeous wood tones that gradually change over time (especially if exposed to direct sunlight). Use these very special Tannin Hand Dyed Threads for all kinds of embroidery, including beautiful Sashiko. To care for your finished project, avoid water with a lot of iron in it, alkaline detergents, and bleach. In the case of accidental exposure, you can restore most of the original color by soaking in water diluted with vinegar or reconstituted lemon juice.