Also, if you haven't already done so, consult the old literature. E.J. Wall's Dictionary of Photography, Cassell's Encyclopedia to name just 2.
Here -> http://books.google.com/books?id=pqk...deners&f=false
Let me know if the link doesn't work. Even though you're using this on modern ink-jet prints, the basic facts and knowledge about hardeners hasn't appreciably changed for over a 100 years (I'm making an educated assumption, but of course could be wrong).