After several days of searching, I finally found the newspaper article
I have that talks about cleans ivory!  It appeared in a local newspaper
recently, but the article itself is from a syndicated column by Anne B.
Adams and Nancy Nash-Cummings, and distributed by the Newspaper
Enterprise Association.

   "Dear Anne and Nan: I have an ivory necklace that is very
discolored, and I am wondering if you could tell me what I could use to
clean it.  It is quite old, and I don't want to use something that
could ruin it.  -- Catharine, Harvard, Ill.

   "Dear Catharine: Here is what the restoration people told us at
Steinway and Sons when we called.  We suggest you try it on one bead at
the back of the necklace first to make sure you get the results you are
looking for.

    "First, clean the beads with 4000-grit steel wool and denatured
alcohol.  Then apply hydrogen peroxide with a wet (not soaking) cotton
ball.  Apply the hydrogen peroxide several times; each time, let the
beads sit and dry for a couple of hours.  If you expose the beads to
sunlight, so much the better.  Then buff first with 4000-grit sandpaper
and then with 6000-grit.  Finally, polish with a buffing cloth --
chamois is the best.

   "P.S. Warning!  If your beads are old and you think they may be
valuable, _don't_ remove the discoloration!  You will decrease the value
of your necklace by half, if not more."

Joyce Brite
Player Piano and Mechanical Music Exchange
http://mmd.foxtail.com/Exchange/