Removing investment from cast pieces

I was just reading the posts on centrifugal casting with diamonds in
place (great I may need that someday soon), and
remembered a tip from a metalsmith I know. She casts quite often, and
has found that if, after she removes the bulk of the investment from
the pieces, she leaves them in white vinegar overnight, the rest of
the investment comes off very easily. I have yet to try it, but it
might help some of you casters out there. Of course, I don’t know how
vinegar would affect a diamond, but (and correct me if I’m wrong) I
would imagine they’d be fine.