Dokumentus Braun is a brown, permanent document ink.
Rohrer & Klingner's "Dokumentus" line of document inks is a DIN ISO 12757-2 certified document ink which means it's permanent: waterproof, UV resistant / lightfast, bleach resistant, ammonia resistant, sulfuric acid resistant, and more. Basically, the paper you write on will disintegrate long before this ink does.
