Platinum Ink bottle, Classic Ink series Yellow-Green ink (Citrus Black - 60ml)

60ml: Dye ink

Blue Black Ink was developed and required for its high resistance to water and light, which was mainly used for official documents that are stored over years.
Firstly, the ink on paper is blue but as time goes by, the ink will slowly change into thick black that will maintain its color for years.
Nowadays, there are only a handful of manufacturers using these procedures.
Blue Black Ink is known for its high resistance to water and light, which makes it suitable for such documents that are being stored for years.
'Classic Ink' is specifically for such purposes and to enjoy the changes of ink over a period of time. It also emphasises the shading of the writing, which is another aspect you can enjoy.
It is a 'living pen'.

Go see in the 'Specifications' section below the PDF file to have a closer look at the ink bottles.