Problem is, Indian Ink now ain't what it used to be. In days of yore shellac tended to be used as a binder. The general solvent for shellac is alcohol.
But if alcohol doesn't shift it (when dried), try panel wipe. If that fails, try acetone (which may do very odd things to O rings, etc. although they usually return to normal if allowed to do so).
I've used calligraphy inks (generally cheap and easy clean!) but prefer acrylic paint - the "airbrush ready" varieties are all over-priced, but clog infrequently, tend not to spider, and respond well to water, proprietary - for acrylic - airbrush cleaner and water. Any variety is likely to be cheaper than a decent Indian Ink and - depending on the paper - you can often erase acrylic.