Rohrer & Klingner fountain pen writing inks feature a range of brilliant colours. The inks are made in Germany and contain specially treated water and minimal additives. This well-balanced composition allows for optimal flow of the ink and provides consistent ink delivery to the fountain pen nib. 50 ml bottle. Salix Iron Gall ink is a blue ink which darkens due to oxidisation, as it is made from iron salts and tannic acid. This ink is water resistant and has a high level of permanence.