You absolutely *don't* want to use contact cement!.  The ivory is somewhat
translucent (see through).  The yellow of the contact cement will make
the ivory appear to be yellow.

I have had the best luck with glue wafers.  What they are is dry glue
imbedded in a white cloth.  It is very similar to what was used
originally.

You clean the key off down to the wood and of course, remove any glue
from the old ivory.  You soak the wafer in water for a few minutes and
clamp the ivory to the key with the glue wafer in between.  This is best
done with a hot clamp.

I get my glue wafers from Schaff Piano Supply in the Chicago area.  The
wafers come with some instructions on how to use them.  Schaff's phone
number is (847)438-4556.

To get ivories, you probably want to talk to any piano repairers /
rebuilders in your area.  I have a small supply.  Usually, when you
replace the keytops on an old piano, there are SOME good ones.  I always
keep them for repairs.  One problem you will have with just any old ivory
is that they may not match very well.  Even when they were new, there
were different grades, grain and etc.  Now that they are old, you want
to try to match the degree of yellow also.  Sometimes, I think poorly
matched ivories are worse than the broken or missing one it replaced!

Depending upon what you are trying to do, you might want to consider
replacing the keytops.  This is possibly easier than finding and
replacing all of those ivories.  If the rest of the instrument is very
nice this would probably be the way to go.  If it has a bit of a rough
look, a new keyboard may make the rest of the instrument even more dingy
looking.

New white (and black) keytops are available from piano supply companies
like Schaff.  I would get the ones with molded fronts.  You remove all of
the old ivories and fronts with an old iron and a damp cloth.  Then, glue
the new ones on with contact cement (this is OK here, the glue doesn't
show through).  The front corners are already nicely shaped.

Getting the ones with molded fronts insures that you get then on even.
Usually, you may need to file the back corners where the key bends.
If you do this, then you will have a supply of old ivories for your next
repair project!

Gary Rasmussen
GRasmus140@AOL.com