Here's what I have used, from this website: http://home.att.net/~rspragg/bonecure.html
PREPARING FRESH BONE
(For Turning)
In preparation of fresh bone (use marrow bone only), cut off the joint ends and then boil the bones in baking soda, it's an alkali and dissolve's grease easily in water), or lime water, (another bleaching agent also called chlorinated lime) with approximately one teaspoon of alum added to each quart of water. Boil this for one to three hours depending on the size and fat content of the bone. Rinse the bone well in several changes of water, and then bleach the bones for several days in the sun and open air.
Another method, which I think is more effective but which demands a greater degree of care, is to cut the bone into pieces of the desired size and after it has been boiled the piece is dried and ready to shape and work. Place the bone in a bleach of 40% hydrogen peroxide (taking care not to burn your fingers) for 24 to 48 hours. This method will give you the best white color results. 40% hydrogen peroxide can be bought at hair salon supply stores.
Another method is to bring to a boil the steer bones in 1/2 cup of enzyme bleach, (Axion, BIZ, ERA, Plus, or Wish), these bleaches attacks the proteins and eats away the fat and meat parts that are on the bone), and simmer for 4 to 5 hours. These bleaches makes the bones white. (may not want the bones white, but natural) Rinse the bones in cold water and scrap away any remaining cartilage material Rinse several times before putting in a fresh pot of water. Repeat this simmering process. Thoroughly rinse again and let dry for up to a week. Bones may be dried in less time in a very low oven.
Make sure that there are no porous parts included in your finish piece. These porous parts will occur around the joints at both ends of the bone and some in the center.