yellow ivories

[Tvak@AOL.COM]

I have read, or heard somewhere, that ivory key tops will yellow if kept in a 
dark place.  If this is true, where do you guys keep your spare ivories?  My 
work area (I hesitate to call it a "shop") is in the basement with no 
windows.  Should I worry about them yellowing even more than they already are?

I tried bleaching one that was particularly yellow, and the bleach didn't 
seem to have any effect.  (I painted the top with bleach and let it sit for 
15 minutes or so.)  Is there a way to whiten ivory key tops which have 
already yellowed?  

Any advice?

Thanks,
Tom S.
Chicago PTG Associate