The ivories on the bottom were soaked in Clorox for 4 days.  The time could be shorter but at least it is not too long. The top ivories show the condition before bleaching.

The clorox is about half and half.  Rinse in clean water dry with a towel place on something like an oven rack or toaster oven grill so both sides can dry together to prevent warping. I dried them outside the oven    ---ric