DIY Skull Cleaning (Contains Graphic Images)

This is the finished deer skull, I was happy to be able to keep the lower jaw intact (with some glue), the only portion I was a little disappointed with was the teeth which are a bit stained.

Why did I clean a skull?

I was listening to a podcast with Steve Rinella who is an American Conservationist, and also popularly known for his series Meat Eater on Netflix. His commentary surrounding hunting regulations, factory farming, and wildlife conservation were new and engaging to me. Given my upbringing, I had little exposure to wildlife and hunting culture, it seems like a way of life that is exclusively passed down through the family. Fortunately, a friend of mine named Matt has some ties to this culture and was able to increase my exposure.

The last time I visited Matt's family farm in southwestern Washington State we stopped by a neighbor's home who shared his collection of skulls and antlers with us. It wasn't odd for me to be interested in something like this, I had taken an anatomy class around the same time and loved looking at bone specimens. In particular, the bone specimens that were actually real bone, not plastic molds. Plastic molds leave you with a blase feeling when you hold them, you know it's fake and a lot of detail is lost. In addition, they all look the same since they're cast from the same mold. When you hold a real bone specimen there's a tremendous amount of detail and variation, there's a clear sense that this was a part of a living animal and it forces upon you a sense of awe when you hold it.

Sometime after this trip, YouTube summed up my various interests and recommended a video by WhiteBone Creations. I guess Steve Rinella + interest in anatomy + physical proximity to Matt’s neighborhood skull guy = skull cleaning video recommendations.Now, as much as I hate the idea of recommended content and the addictive properties of how that is typically implemented, I do have to give some credit here, the recommended video was a good fit. If the opportunity presented itself I would absolutely be interested in attempting to clean a skull myself.

WhiteBone Creations is a small company that cleans skulls and briefly documents the process via their YouTube channel. They share enough information to help you get started yourself but not enough detail to replicate their quality of craftsmanship. The biggest barrier to entry is that most people would be put off by the process, it's a bit gruesome. I continued researching bone cleaning techniques and let Matt know that if it wasn't a hassle I'd like him to save the head of his next hunt so that I could try to clean the skull myself.

Methods For My First Attempt

I received a call from Matt on a Sunday night, he had a successful bow hunting trip and came home with a deer. I immediately met him to begin the skull cleaning process that I've documented below.

  1. Removing the hide from the head

This was harder than expected, in the videos I watched they cut through the hide very easily. Though my blade was sharp I think their blades were, well, extremely sharp. Though a bit time consuming, I eventually stripped off the hide.

2. Separate the lower jar from the skull

The jaw was clamped shut, I had to make four incisions through muscle tissue in order to release the jaw. When prying the jaw open be careful to not cut yourself on the teeth.

After removing the hide, the jaw is clamped shut and in order to separate the lower jaw, you need to cut through a few muscle groups.

3. Remove loose tissue

I didn't have the proper tools for this step. I did the best I could with my limited tools but would pick up better tools the next day.

4. Boil the skull in a water and sodium bicarbonate (baking soda) solution

From this step onward skull cleaning hobbyists and experts vary in their methods. Some recommend baking soda, some soap, some just water. Some said to boil, others to simmer, some no heat at all. You can even clean the skull with dermestid beetles, skipping any chemical treatments. Each option has tradeoffs to consider which I discuss later.

I made a solution of water and sodium bicarbonate, about 1/2 cup of sodium bicarbonate per gallon of water. I boiled the skull in the solution a total of three times for about 30 minutes each. I obtained some pottery/wax carving tools that were extremely effective at scraping tissue as well as three small wire brushes made of steel, copper, and nylon. I also hosed off the skull with a nozzle set to "jet". After the third boil, I started to notice the bone was deteriorating a bit. I'll touch more on this later, but in hindsight, I probably shouldn't have boiled as aggressively as I did, a light simmer may have been sufficient.

The boiling process was shockingly effective, in hindsight, I think I may have boiled the skull too aggressively.

5. Degreasing the skull

This was a last-minute decision, I read some folks that soaked their skulls in soapy water to "pull out" grease. Since I had the time I went ahead and soaked the bone for about 30 minutes, visually it was hard to say if it did anything.

After three boiling sessions in a sodium bicarbonate solution, I soaked the skull in a soapy solution to pull out as much grease as possible.

6. Whitening process using hydrogen peroxide

I used 3% hydrogen peroxide (what you find at the store) to whiten the skull and it was very effective. There's a few whitening techniques out there (various concentrations, and so on), but this was what I had access to on short notice. I soaked the skull for about 24 hours overnight. I'm glad I kept an eye on it since the hydrogen peroxide was definitely degrading the bone and thinning out.

After degreasing, the bone soaked in a 3% hydrogen peroxide solution for about 24 hours.

7. Drying process

I wrapped the bone in paper towels to dry for 2 days, replacing the paper towels and hand drying a few times a day. I think a blow dryer would be useful here to accelerate the process.

This is the bone during the drying process after having soaked in the hydrogen peroxide bath.

8. Gluing broken pieces together

The lower jaw split on me during the boiling stage and a couple pieces from the upper jaw fell off as well. All advice online pointed to using Elmer's glue so I went ahead with that method and it worked great. The lower jaw needed a wooden dowel in the back for support.

The lower jaw split, most likely due to over boiling in the early stages. I glued it together at the tip and glued a wooden dowel in the back for support. Nearly all skull cleaning sources online recommended Elmer's glue believe it or not.

9. Finishing touch with Mop & Glo

I picked up this tip from WhiteBone Creations, lightly brushing on Mop & Glo gives the skull a nice sheen.

The finished upper and lower jaw, the Mop & Glo gives it a natural-looking sheen.

10. Assemble for the photoshoot

Here is the skull assembled for display, it was important when gluing the lower jaw in the previous step to make sure it would fit with the upper jaw. I would love to get a vintage glass display box to hold the skull, but I haven't found one that I like quite yet.

The finished skull, no photo editing was done on any of the photos in this post, it's legitimately this white and this clean looking.

How To Improve For Next Time

The results of my first attempt turned out surprisingly well. I solved problems as I encountered them and wasn't afraid to improvise. Common sense and intuition proved to be great guideposts to follow. With that said there are a number of things I would do differently next time.

First off, a sharper knife to remove the hide is mandatory. The amount of force required to remove the fur was a stark reminder of how squishy humans are. The process I used for loosening and removing tissue from the skull could use the most revision. There are a number of factors you're trying to balance, ideally, the process is quick, makes the tissue easy to remove, does not degrade the bone, does not produce a strong odor, and is cheap. I chose the sodium bicarbonate boiling method because it was quick and cheap, and I assumed it worked to some degree since it was recommended consistently online. It turns out though that there is quite a bit of research on the various methods (I wish I had found this beforehand).

In 2006, Steadman published a paper investigating various maceration techniques to facilitate skeletal analysis by forensic anthropologists. He devised a wonderful scoring system shown below.

Steadman's scoring system ranking odor, soft-tissue texture, ease of flesh removal, and bone quality.

The scoring system addresses all the tradeoffs one would be concerned with (excluding cost). Steadman scored odor, soft-tissue texture, ease of flesh removal, and bone quality, as well as the exposure time to the maceration technique. The results are his experiments are shown below.

The results of various maceration techniques, the experiment most comparable to my method is Biz/Na2CO3 (90 C).

We can actually see the technique I used, Biz/Na2CO3 (90 C), though mine was more like 100 degrees Celsius. My experience falls in line with the score Steadman arrived at as well. The odor was not an issue, the soft tissue was noticeably looser, and I noticed some bone erosion. Where my results differed was the average ease score. I would've given a score of 2. But his table indicates the solution was kept at 90 degrees Celsius. My solution was certainly boiling at 100 degrees Celsius, so we can compare the boiling experiment in the above table and we see the average ease score increased to 2.7 which makes sense empirically.

The beauty of this table is that it will inform my next skull cleaning project. I would like to maximize ease and bone quality while minimizing odor and to a lesser extent time. With that in mind, it seems like just boiling the skull in water is the best approach.

The results of this study were fascinating because it contradicted much of the advice I read on forums online. The one method I wish Steadman would have tried was the use of dermestid beetles, they provide incredible results, preserving intricate and fragile bone structures, especially sinus cavities. If you ever see a skull with intact sinus cavities, such as teh skull below, almost certainly beetles were used.

The only way to keep intricate structures intact is dermestid beetles, all other methods are too aggressive to my knowledge.

References

Steadman DW, DiAntonio LL, Wilson JJ, Sheridan KE, Tammariello SP. The effects of chemical and heat maceration techniques on the recovery of nuclear and mitochondrial DNA from bone. J Forensic Sci. 2006 Jan;51(1):11-7. doi: 10.1111/j.1556-4029.2005.00001.x. PMID: 16423217.