50 ml plastic bottle of Rohrer & Klingner Dokumentus, Green (Document Ink)
dokumentus is the world’s first fountain pen ink conforming to the resistance requirements of DIN ISO 12757-2.
New technology and high quality raw materials used to formulate this new pH-adjusted ink guarantees permanent and archival writing. Comfort of writing with a fountain pen was the main focus of this new product development. Do make sure to replace the cap on your fountain pen after use to prevent blockages in the nib. Beyond this no special care is needed!
ISO 12757-2 certified means they are not erasable, resistant to ethanol, hydrochloric acid, ammonia resistant, bleach resistant, water (obviously) resistant and are lightfast.
There’s also another standard, ISO 14145-2 which some other manufacturers use like Montblanc.