Fresh bones are filled with natural oils and fats, aka grease. To achieve clean bones that don’t stink or form grease spots later, this grease needs to be removed. This tutorial is about degreasing fragile animals such as reptiles, birds, and baby mammals. I’m not going to do a tutorial on degreasing sub-adult to adult mammals as there are a plethora of write ups on this subject already, and they are easy to find. However, I have found it hard to find information on degreasing fragile animals.

Needed Supplies

To start with it is important to mention WHY fragile animals need to be degreased in a different way. When using standard methods such as diluted ammonia or dawn dish soap and water with heat, the unfused skulls of baby mammals, and skulls of all ages with reptiles and birds, will absolutely fall apart into several pieces. Over 50 separate pieces with certain species of snakes. This is obviously not ideal, especially with tiny skulls that are verging on impossible to reassemble.

Now, don’t get me wrong, there are people that macerate and degrease these types of animals with standard methods and then painstakingly put the skulls back together, but none of that is necessary. If you use Dermestid Beetles to remove the flesh instead of maceration (which will also cause them to fall apart), and follow this method for degreasing, the skull will not fall apart. Neither will Ligament Mounted* skeletons. Much more ideal, and to me it ends up as a better piece as the skull is in it’s original natural form and position.

This example is a hatchling Water Monitor coming out of his egg that I built. This piece would have been near impossible without this method as the specimen was incredibly fragile. Using this method I was even able to preserve the egg tooth.

Let’s assume you have already beetled the specimen and are ready to degrease. The best solution you can use to maintain the shape and ligaments that are holding the piece together is Acetone. Undiluted, straight out of the can, Acetone. Now Acetone is flammable, so use common sense when working with it. It is also known to cause cancer and other health issues, so always wear a respirator mask when working with it.

When you place a full freshly beetled skeleton or skull into Acetone (using metal tweezers as it is bad for your skin and will melt rubber gloves), it will come back out in the exact position it went in. Acetone does not moisten the ligaments, causing the piece to either fall apart or go limp, the way other methods do. This is ideal for small and fragile specimens, and the sole reason I use Acetone. It is a more expensive method, for sure, but you make up the cost in time saved and the frustration it saves you.

Pour the Acetone into an Acetone safe container such as glass, PP or HDPE plastic containers. Most plastic containers have this information molded into the bottom of the container by the recycle logo. I typically use Ziploc Containers as they are air tight, cheap, and Acetone safe. Make sure whatever container you use has an air tight lid as Acetone evaporates rapidly and the gas is toxic. You just need to use the smallest container possible to fit the specimen in and fill with Acetone just above the highest point of the specimen so that it is completely submerged in the Acetone.

Once this is done, simply place it on a shelf in a room that doesn’t get very hot or have any open flames. Now the waiting begins. You will see the fluid start to change colors over the next day or weeks even. It starts crystal clear and begins to yellow as it dissolves the grease from the bones. Once it is a deep amber color the fluid needs to be changed. I continue to observe the container and change fluids as needed until it finally quits changing colors. Once it goes 5 days or more without changing colors, the animal is typically done degreasing and can move on to the next step, whitening.

This process can take just 5 days with small specimens that are naturally not greasy, or months with things such as tortoises which tend to be very greasy. Just keep observing and changing fluid until it stays clear. Don’t give up, it’s a waiting game for sure, and there is no set amount of time with any animal.

I usually keep one container going for small skulls only as they never change the color and the acetone is still usable. I have processed dozens of small skulls in the same container of acetone without changing fluid. This only really works with small skulls and bodies.

Once you think the animal is degreased, remove it from the Acetone with metal tweezers or tongs (not your hands, and keep in mind Acetone melts rubber gloves). Let it dry and sit for several days and see if any grease starts to appear. I typically whiten and then do this, purely because with whitened bone it is much easier to spot grease. If any pops up, I just throw it back in Acetone and start again.

It is not safe to heat Acetone, and as it is very powerful at dissolving grease without heat, it also isn’t necessary. So just keep it at room temperature.

Please dispose of used Acetone in a responsible way. Most towns have places you can take it to for proper disposal. You can dump used Acetone into a PP or HDPE 5 gallon bucket and take it to be disposed of when it is full.

*Ligament Mounts are small specimens where the beetles are stopped after all meat has been eaten but the ligaments are still holding all, or at least most, of the bones in place. This is ideal for fragile and tiny species.