The 24k gold ink is a nanoparticle pigment, held in water, and was offered with an introductory price of around 139 euros but is meanwhile situated at around 290 euros. Document-proofness and water resistance arise only on drying on the paper; before that the ink behaves like a normal water-soluble ink. For cleaning the pen, therefore, clear tap water suffices; important is not to leave the pen unused too long, since the ink otherwise clumps and solidifies. Collectors voice concerns about the high price and see in a second pen the more sensible investment.