Natural Dye Extract ChestnutColors: Parchment to Elephant Grey Sweet Chestnut or Castano is native to Italy and Southern France. It contains between 5% and 10% tannic acid. It is a subtle dye, used primarily as a base for other colors. Chestnut is used extensively in the leather industry. It can be used with Iron for a warm grey or Alum producing a pale yellow. Overdyed with Indigo it provides the color Mallard Green.