Hi Ronald,
Cleaning bones is a whole different ballgame from cleaning shells.
Bones contain fat - shells do not.  If the fat is not removed, it
will gradually decompose and discolor over time, turning the bone
first greasy yellowish, and eventually an ugly brown color.  Those
who prepare study specimens of skulls and skeletons use organic
solvents to quickly dissolve out the fat.  Such solvents include a
variety of nasty substances that I do NOT recommend for home use,
such as toluene, benzene, chloroform, and carbon tetrachloride.  Some
of these are very toxic.  I believe something like mineral spirits or
paint thinner would work adequately, but even with these "safer"
solvents such procedures should be done in well ventilated areas,
away from sources of flame or sparks (including electric motors of
ventilation fans).  Outdoors is best!  Alcohol is not a very good fat
solvent.  I would soak them for at least several days, if not a couple
of weeks, during which time the solution should be changed regularly.
Before any such solvent is used, the bones have to be thoroughly
dried.  These solvents are not miscible with water, so if there is
water in the bone, it will keep the solvent out.    Once all the fat
is extracted, the bones only need to be dried.  They don't need
bleaching, as they will dry white and remain that way.  If they later
begin to yellow, you didn't get all the fat out.  A strong detergent
solution might be worth trying as a fat solvent, though generally the
non-aqueous solvents work better and faster.  Both bleach and acids
should be avoided.  Bleach (and other strong alkalis) will dissolve
the bone matrix, leaving only the calcium salts.  A friend of mine
got a deer head from a hunter, and wanted to prepare the skull.
After carefully dissecting away all the muscle and other soft
tissues, he put the skull in a potassium hydroxide (roughly
equivalent to drain cleaner) solution, to remove small pieces of
tissue that remained.  However, his specimen preparation was
interrupted by a 2-week family vacation, during which time he left
the skull in the solution.  When he returned, he looked in the bucket
and saw what looked like a perfectly clean, pure white skull.  But
when he grabbed it to pull it out, and the whole thing crumbled to
bits.  Acids have just the opposite effect.  They won't dissolve the
matrix (unless the acid is very strong), but they will leach out the
calcium salts, leaving a softened, cartilage-like material which may
shrink and become distorted when dried.
Paul M.