It’s recommended to write documents with this ink ONLY
The documents written with this ink can not be washed out with water or bleached with any acid or alkali.
They are really permanent. Light fast too.
The ink is iron gall type. When kept in an un used pen, this ink can corrode the metal ( That is Steel nib). NO PROBLEM FOR GOLD NIBS. I recommend to wash the pen at least in a week when using this ink continuously.
The color of the shade change from Blue black to black.