Iron gall ink was an indelible ink used on sailboats from the 12th to the 19th century. It goes down brown and then dries into a dark purply black. It doesn’t fade in the sun or wash away in the spray. J Herbin was a sailor and his first ink recipe was for Iron Gall. His second was called, "La Perle des Encres" (The Jewel of Inks), a recipe brought back on one of his many journey’s to India and refined for years afterwards. It went to market in 1700 and is still in production in France. PH neutral, all natural dyes, water based, fast drying, 30 beautiful, prismatic tones.