I've done calligraphy for years and I can confirm what you've found out.
The true permanent inks, especially the chinese inks, will rust your
good pens. Gouche works great! As well as Dr. Martin's watercolors. With
the gouche, you will want to add a drop of gum arabic to help with flow.
On Monday, April 1, 2002, at 07:28 PM, Virginia Rockwood wrote:
After teaching calligraphy for a bazillion years I just read that
permanent inks should be avoided for use with dip pens. Apparently,
(this means india ink) contain a varnish which helps the ink be
permanent when dry. No more will I soak and gently scrape india
buildup from my expensive pen nibs. We use concentrated watercolors for
ink now. . . . .