Meanings of ink wash in English

So why did some voters' ink wash off under a stream of water, or, worse, by a forceful touch?

Waves of dark green ink washed down his forearms, lapping at his wrists.

Romany sagged, his tenuous confidence abruptly eradicated like fresh ink washed from a page by a gush of ice water.

In most cases, india ink did not significantly inhibit detection with antibody, nor was the ink washed off during the antibody incubation steps.