@Helene
Chinese ink is pigmented and will clog the pen. It's best to ink that flows better, Rotring (black) and Noodler's Bulletproof Black are good if you need waterproof quality.
Otherwise, you can use any dye based fountain pen ink.
Washing is not necessary, but it's definitely good to do so if you are not going to use the pen for weeks.
@Helene
Chinese ink is pigmented and will clog the pen. It's best to ink that flows better, Rotring (black) and Noodler's Bulletproof Black are good if you need waterproof quality.
Otherwise, you can use any dye based fountain pen ink.
Washing is not necessary, but it's definitely good to do so if you are not going to use the pen for weeks.