How To Clean A Skull
What You'll Need
Before attempting a skull project, make sure you have the following in order:
1) A skinning knife or bone saw
- A sink to clean the skull over when you take it out of the pot
3) A stove-safe pot large enough to fully submerge the skull in water
- Tongs for grabbing the skull out of the hot water
4. Tools for pulling or scrubbing off pieces of flesh (old toothbrushes, tweezers, etc; old dental or surgical tools work great for this)
5) A or two to safely organize teeth or small bones that become dislodged during the cleaning process compartment box
7) An aquarium heater or under tank heater (optional)
8) Hydrogen peroxide 3%
9) A plastic or glass container that will fit your skull pieces while you whiten them
10) Gorilla Super Glue
1: The Detaching Process
Definitely the most grisly of all steps illustrated here, detaching a skull requires a strong stomach, patience, and some understanding of cervical anatomy. If you're lucky, you'll find an already detached skull, but more than likely you will have to face this challenge.
There are a few ways to remove a skull from a body, but the best way would be to use a sharp bone saw, making sure to cut vigorously through the neck at a safe distance behind the head (the "safe distance" is harder to judge with smaller animals such as rabbits, but aiming for the middle of the neck is your best bet). Skulls are often deceiving and can be longer in the back than you would think, so be careful not to saw too close to the back of the head.
Another method of skull removal is by use of a sharp skinning knife. Cut a complete line around the neck as if you were attempting to skin the animal, and peel away the neck skin so that you have a clear view of the muscle of the neck. Then, using the tip of the knife, you can sever the tissues, muscle, and spinal chord between two of the cervical vertebrae (this is easier to do the further away from the skull you attempt it). Once all tissue keeping the two vertebrae together is severed, the skull will come away (with a few vertebrae attached). But don't worry, any cervical vertebrae that remains attached to the skull side will eventually detach in the pot.
Once you have the head removed, it is important to remove the skin on the head so that there is no flesh covering it. The skin is a powerful organ that can be difficult to get rid of once it's in the pot, and removing it can cut down on the maceration time. Removing the skin will require a skinning knife and some patience. Extreme care must be taken when wielding the knife that you do not cut into the bone of the skull at any point. It is best to aim the sharp end of the blade upward, and never saw downward into the skull. Generally I prefer to remove the skin, eyes, and larger cheek muscles attached to the mandibles and the muscles along the sagittal crest of the cranium before I move on to Step 2.
Boiling vs. Simmering:
Simmering is distinctly different from boiling. Never boil a skull - the extreme heat will dry out the bone, crack the teeth, and eventually "melt" away the sutures that keep the skull itself together. Boiling is a technique that many hunters use, but it can actually do more damage than good. In contrast, simmering a skull in water that is just over the threshold of being comfortable to our touch (but not boiling) is where the tissues of the skull will cook, shrivel, loosen, and slough off, leaving the bone unmarred. We are aiming for an approximate temperature of 170° F. It is unnecessary to bring the water to a boil when the same effect can be achieved at much lower temperatures.
2. The Simmering Process
This is where it all starts to happen. You need to be aware of multiple things before jumping in on this one:
This is where the teeth will loosen and fall out. Learn how many teeth your animal has, and draw a diagram beforehand if it will help you know where they all go. In preparation for when the teeth come out, have a place set up where you can line them up or store them in order (this is where your compartment box will come in handy). You will need to glue them all back in once everything is done, so do not take this lightly or you will get confused! Be vigilant, the heat will loosen most of them, and many will fall out of their own accord.
With most mammals, the bottom jaw (the mandibles) are two separate pieces fused together. There is a suture called the Intermandibular symphysis that runs right down the center of where the left and right mandibles meet which will invariably loosen in the simmering pot. Subsequently you will soon have two pieces for the mandible, the left and the right, which you will glue back together when everything is finished.
You will be required to check on the pot every 20-30 minutes, taking out a piece at a time and picking off the softened flesh with a pair of forceps, hemostats, or tweezers. You want to get whatever you can to come off the bone as soon as its loose enough to be pulled off. The longer pieces of meat are stuck on a bone, the more likely it is that the greases and fats of said meat will seep into the bone, discoloring and potentially leaving grease stains behind. A big mistake a lot of first-timers make is leaving the skull in the pot to simmer unattended, believing that all the sinew and muscle will come off on its own. Unfortunately things are not so simple. Undoubtedly this is the most grueling of all the steps, and it will require extreme patience and perseverance.
This part of the process can easily take 1 or 2 hours, depending on the size and freshness of your skull, and how meticulous you want to be. You may want to wear gloves during this process, otherwise your hands will get dry due to washing the skull under the sink for so long! Conversely, sometimes gloves can prevent you from being able to feel loose teeth or bone vs. tissue as easily, so you may find it better to not use them.
- You will start by filling your stove pot with hot water and then bringing it to the appropriate temperature. A cooking thermometer can be used for this. Aim for a temperature approximating 170° F. If desired, you can mix in some Biz solution to help soften up the flesh on the skull, but this is not necessary. Once your water is the desired temperature, add the skull and let it sit for approximately 20-30 minutes.
- Remove the skull with a pair of tongs and take it to the sink. With some forceps, try to pick at any obviously loosened flesh and peel it away. Soft muscles like the ones around the cheeks and jaws are usually easiest to remove first. Be gentle, don't force it - if you can't remove a particular piece of flesh, put the skull back in the pot and let it sit another 20 minutes or so. Repeat this process until the bone is free of all meat. Care must be taken to avoid breaking or marring the bone. Don't pull, tweeze, or push too hard, especially in delicate areas such as inside the nasal cavity or around the Auditory bullae. Beyond removing the leathery flesh of the nose, I don't even bother with the nasal cavity until much later.
- Eventually you will find that the brain within the skull has begun to break apart and some particles may be coming out of the back of the skull. Once this happens, you can clean out the brain case by running water from the sink faucet directly into the Foramen magnum, shaking the water around inside the brain case, and then dumping it out. Repeat this process as necessary. You should not need to insert any tools inside the brain case to stir anything loose, as the brain will eventually liquify completely in the hot water pot and you can clean it all out with water from the faucet.
- Changing out the water in your pot may be necessary at some point, especially with larger skulls. Whenever I feel the water is too murky or full of debris, I like to start over with a fresh new batch of water. Repeat the process as needed or desired.
- As the skull becomes cleaner and more flesh is removed, frequently allow water from the sink faucet to flow from the Foramen magnum down through the nasal cavity, and vice versa, to clean out the sinus area as much as possible. There is a lot of pesky flesh that likes to get stuck in those areas, and by using the pressure of the sink faucet you can do your best to dislodge those pieces without causing any damage to the bone. Do not ever use tools in the nasal cavity regardless of how much material you think is stuck in there, it will come loose in the next few processes.
Eventually you will come to a point where all of the major pieces of flesh have been removed, but you may still have some sinewy looking material stuck to places like the nasal cavity, Mandibular condyle, and Auditory bullae. These white or clear-colored bits of flesh are fine, and as long as all the colored chunks of meat are removed and the skull cavity is as cleaned out as you can make it, you are ready to continue to the next step.
The Wisdom of Teeth
The removal of teeth is an important part of the skull cleaning process. The roots of living teeth are filled with nerves and blood, and if teeth remain anchored inside the skull of a dead animal, oftentimes those once-living systems can migrate to the surface and eventually tarnish the teeth from the inside out. For this reason, it is a good idea to remove any teeth that you can.
Teeth are fitted inside the bone of a skull through means of Periodontal ligaments, which anchor the tooth root tightly to the jaw of the skull. During the Simmering Process, most teeth will loosen and many will come out easily or of their own accord (typically the incisors and canines). However, some teeth, like molars and premolars, may be extremely difficult or downright impossible to remove without damaging the skull. The molars found on herbivores such as deer are deeply rooted and tightly packed, and likely will never be coaxed out regardless of how hard you try. Do your best, but don't force it. I often leave the molars of herbivores rooted in the skull, but with carnivores I make sure to remove all teeth so that I can thoroughly clean everything.
Biz Stain Fighter:
Biz solution can be found at most grocery stores in the laundry detergent aisle. It is similar to baking soda or Borax, but entirely different from these; I feel it is an integral part of my skull cleaning process. It works as a degreasing and conditioning product, and it transforms my skulls into works of art that are smooth to the touch and free from grease. I highly recommend this product, and I cannot guarantee the quality of skulls that are cleaned without it!
3. The Degreasing Process
Degreasing, soaking, final maceration, call it what you will, but the main idea here is to place the skull in a bath of water mixed with Biz (or Dawn dish soap) solution for a few days to a few weeks so as to get rid of any remaining flesh and to try to coax any leftover residue out of the bone itself. There will undoubtedly be some pesky bits of flesh still clinging to your skull's hard-to-reach places after the Simmering Process - bits that hot water alone simply cannot get rid of. In addition to this, greases trapped within the bone itself can leave unsightly yellow smears on the bone surface, persisting even after whitening solution has been applied. This does not make for a pretty looking skull, and it's the reason this degreasing step was invented.
Many taxidermists may go about this process differently. Some place aquarium heaters in the water to keep it at a roughly 70-90° F while it degreases, some will place under tank reptile heaters under a metal pot filled with water to keep the water just above room temperature, some will simply leave the skull in the water at room temperature for months. Some may even forgo this process entirely, but in my experiences this step is crucial in removing the last particles of greasy flesh. You can use the same pot you used to simmer the skull in for this process.
- Fill the pot with enough warm water to cover your skull completely, and then add Biz to it, mixing thoroughly so that there is very little to no powder sediment on the bottom of the pot. The idea is that you want the soap to dissolve evenly in the water so that the skull will be soaking in a well concentrated mixture. I generally add 1/2 to 3/4 of a cup of Biz per 1 gallon of warm water, but this is not an exact science. The water should simply feel slimy.
- Gently place the skull parts (you will either have 3 parts - the cranium and left and right mandible - or two parts - the cranium and fused mandibles) into the pot with teeth facing upward. This will help prevent teeth from slipping out in the soak and you losing them in the murky water. If you are using a water heater, make sure that the heater is not in direct contact with any bone, as it could burn them.
- Let the skull sit! You may notice an oily film developing on the water surface over time, this is the grease being lifted from the skull. Depending on the skull size and the species, the degreasing process can take anywhere from a day to over a week. For example, pigs are notorious for being difficult to degrease, and will require more time than a coyote.
- For very greasy specimens, it is recommended to replace the soap water mixture every other day to prevent any extracted grease from saturating the bone and therefore to prevent the bone from retaining a horrendous smell! Keep your water clean, warm, and above all, soapy!
Any teeth or small bones that fell out during the Simmering Process should remain in the compartment boxes you placed them in. Do not worry about degreasing those items, as they generally do not need it. However, you will include them in the next step.
Hydrogen Peroxide Facts:
Hydrogen peroxide (H2O2) is a simple combination of water and oxygen, and it is used for a great many things both clinical and cosmetic. But there are a few things one should know before popping open the top of these opaque bottles:
- Heat denatures the properties of H202, and just a few hours in a hot car can cause the oxygen to separate from the hydrogen, leaving only water behind. Store at room temperature or slightly cooler.
- H202 is light sensitive, which is why it is sold in opaque containers. Do not expose hydrogen peroxide to a lit room for long periods, or the oxygen will eventually separate from the hydrogen, leaving only water behind.
- Hydrogen peroxide may be rendered ineffective if it is placed inside an air-tight container, because it needs oxygen in order to activate it, and it also produces oxygen gas as it whitens the bone. Sealing H202 with a skull in a tightly lidded container may not only prevent the H202 from achieving its full potential, but also may cause undue pressure within the container (and possibly cause the top of your container to blow off entirely).
- Many metals are catalysts for H202, which mean that they cause it to become denatured and return to plain water. For this reason it is never a good idea to store Hydrogen peroxide in a metal container. When whitening skulls, use plastic or glass containers instead.
What's in a name?
Not all Hydrogen peroxide is equal! Hydrogen peroxide comes in a few different concentrations and grades, but the one I use for the purpose of skull cleaning is the standard, over the counter 3% that one would find in dark bottles at the grocery store, down the same aisle as band-aids and topical ointments. Other concentrations, such as 35%, are too powerful for skull cleaning and may damage the bones if care is not taken.
4. The Whitening Process
Standard Hydrogen peroxide (3%) has the power to transform skulls that are yellowed, mottled antiques into beautiful, milky white works of art which do not tarnish over time.
When preparing your skull to be whitened, locate a suitable container that will be able to comfortably fit your skull pieces but will not be wasting a lot of space. For example: a raccoon- or cat-sized skull will typically be able to fit loosely into a thermos-sized container. A smaller container like this (as opposed to the simmering pot or a standard 5 gallon bucket) will allow you to use less hydrogen peroxide and will make it easier for you to store.
If your skull has antlers, wrap each antler from the burr upward with a plastic trash bag and then tape each bag tightly in place to prevent any of the hydrogen peroxide from touching any part of the antler (whitened antlers are not standard practice and can make your skull look unpresentable).
- Once you are finished with the Degreasing Process, thouroughly and completely wash your skull under warm sink water, making sure to remove all soapy residue from the surface and within the brain case and sinuses of your skull.
- Set the skull into a bath of Hydrogen peroxide and let it sit for 12-24 hours. I have never had to soak a skull for longer than 24 hours, and with skulls that are not very greasy or are quite small (deer, rabbits), 12 hours may be fine. Check your skull at the 12 hour mark to see if the color is to your liking. If not, another 12 should do it.
- The teeth that you still have placed in the compartment box should also be whitened with hydrogen peroxide at this time. Simply pour the H202 gently into each compartment containing a tooth and then close the lid. I like to cover both my teeth and skull containers with a dark towel or make sure that they are kept in a dark room until I am ready to take them out.
- At the 12 or 24 hour mark, check your skull and teeth. If the color is to your liking, take the skull out of the solution and rinse thuroughly. Any H202 residue on a skull can show up as chalky white dust once it is dried, so be sure to clean it fully. Hydrogen peroxide's effervescent quality provides some mechanical benefit in loosening any remaining flesh still sticking to parts of your skull, particularly in the nasal cavity, so don't be surprised if you see fleshy bits sloughing off.
- It is at this point that you should check your skull from snout to brain case. Make sure all the flesh you want to be gone is gone. If there are still pieces here and there, the Hydrogen peroxide will have softened them enough for you to easily tweeze them out by gently using your tools or by using the faucet on full power. Once the skull is to your satisfaction, let it sit somewhere to dry completely. Some people like to sit their skulls out under the sun, others may simply set them in a warm, dry room.
- Hold the lid of your compartment box closed tightly and hold it upside down over the sink so that the Hydrogen peroxide can seep out through the corners but all of the teeth remain in their specific compartments. Once the Hydrogen peroxide is drained out, fill the compartments up with plain tap water, and repeat the process of holding the lid closed and draining out the water. You can repeat this process a few times before individually washing each tooth under the sink to make sure there is no H202 residue or flesh remaining on the tooth roots. But be careful! I recommend putting a rubber stopper in the sink just in case you drop a tooth. Once each tooth is cleaned, return it to its respectful compartment and let them all dry completely in the container with the lid open.
Gorilla Super Glue
For my skull projects I use a product called Gorilla Super Glue. I use it because it is strong, dries quickly, is completely translucent, and comes in a handy applicating bottle. I find that I need to use very little in order for it to bind things securely, whereas with some other glues I've used I found myself needing to reapply coats. I also like the nearly instantanious drying capabilities. However, any translucent super glue should be appropriate for this type of project, do not feel as though Gorilla Super Glue is your only choice of product.
5. The Gluing Process
This is the home stretch! You're almost done! Now it's just time to glue everything together. With this step comes an amount of artistry. The basis of art itself is to appear seamless, and as such you want your skull to look as if it is entirely natural in its current state. Hideous, yellow glue droplets around the teeth are a dead giveaway to shoddy worksmanship, so it is important to use glue that dries translucent as much as it is important not to use too much glue in general. Literally just a touch of Gorilla Super Glue will stick teeth in their place. Dab it, don't dollop it!
- With your completely dried skull, take the two mandible pieces (if applicable) and place them together until the knobs of the bones seem to fit into place. Try this without the glue first, just to get an idea of how you will put them together. Once you are able to visualize where the mandibles meet, place a small amount of Gorilla Super Glue to each mandible at the joint and press them together in the position they naturally fit in. If there is any glue that gets squeezed out between the two pieces you can quickly wipe it away with a hot, wet washcloth, or simply touch it with your finger to lift the glue away (keep in mind thoug that the glue will now be dried to your finger). Hold the mandibles in place for a few minutes to set, and then place the glued piece down to completely dry for 10-20 minutes.
- While you're waiting for the mandibles to dry together, take the teeth you've set aside that fell out from the cranium and make sure they're all in order by placing each one in its respective socket. Do not glue them in until you are certain that they all fit (with the exception of some molars which may be too difficult to pull out again once you push them into their socket - instead, set these ones near their sockets). You may need to look at images online of the animal species you have to determine whether or not your teeth are in the correct place, but if you used the compartment box correctly you should not need to do this.
- Starting with the largest teeth, remove one tooth at a time, applying a small amount of Gorilla Super Glue into the tooth cavity or just on the end of the tooth root before inserting the tooth back in. You will know you used too much glue if it starts to spill out of the socket once you push the tooth in. Have your hot washcloth handy, or quickly use your finger to wipe away any excess. I start with gluing in the canines, then incisors, then premolars and down to the molars. Once all teeth are in the cranium, let them set to the skull with the teeth facing upward.
- Return your attention to the lower jaw now. Following the same process, place each tooth in its socket before gluing them in. Once you're sure of where they all go, add some glue to each socket (or tooth root) and place it into the socket. Let dry.
- Reunite the cranium and lower jaw at last. You now have a fully completed skull!
I hope that this walkthrough helped some fledgling taxidermists out there. This is a topic I am very much passionate about and I am happy to engage any fellows in the ways of such an amazingly fulfilling hobby. Skulls can be used for decoration, jewelry, costume design, and reference material, but above all else, they are works of art and should be treated as such.
Now that you have finished your skull, I'm sure you must feel proud! Share your story and your projects with me, I'd love to hear and see what everyone is doing with my information! Please feel free to ask me any questions you may have as well if they aren't answered in the FAQ section.
Frequently Asked Questions
o Where do you find your skulls?
Most of the skulls I find are roadkill specimens, or I have come across them while hiking in the woods and deserts. Occasionally some are gifted to me by animal and wildlife hospitals. I have never personally killed any of the animals I work on and I do not condone the killing of animals solely for their skulls.
o Should I do this indoors or outdoors?
This depends on your state, your living situation, and your comfort level. Being that I live in Washington state where it is very cold and rainy most of the year, I have found that doing my work outdoors is nearly impossible and doing it indoors is much more comfortable. There can be some odors associated with the initial simmering process, especially with large and greasy skulls such as those of the porcine sort, but it has never bothered me before and I have always likened it to strong chicken or ham stew. For me, the convenience of having good lighting and a sink nearby is worth it, but with exceptionally large skulls, an outdoor stove may be your only option.
o Can I get sick from doing taxidermy?
Being safe and sanitary is important in this line of work. It is pertinent to wear gloves when dealing with dead animals to prevent zoonotic bacteria or parasites from harming you. There are a number of parasites that humans can get from animals, and nasty bacteria from diseased flesh can easily cause septicemia if you have an open wound on your hands. Some animals can carry leptospirosis, raccoon roundworm, even leprosy! Healthy adults are less susceptible to these problems than are children, the elderly, and the infirm, but it is still good sense to use precautions and be aware of the risks involved. It should be noted, however, that at the final stage of cleaning, once the hot water, soap and Hydrogen peroxide have had a chance to do their magic, a skull is technically clean enough to eat off of.
o I have a skull that has a grease/algae/mold stain that I can't get rid of!
There is some charm to weathered bones, but if you have already tried to degrease and/or whiten to no avail, you can always turn your less-than-perfect skull into a beautiful art project instead! By carving, gluing, using acrylic paint, alcohol ink, spray paint, watercolors, or any type of medium you can think of, the number of things you could turn your skull into is endless! So don't feel bad. There is always a way to make any skull look amazing. For more information and to get some ideas of what to do with your grade B, C, or lower skulls, visit my craft Hub here!
o I don't want to use this method, what other types of methods can I use to clean skulls?
Truly there must be as many methods for skull cleaning as there are skulls on earth! Some people employ the burial method, where the skull is buried in the ground in a mesh or wire container and left to sit for months. This allows the enzymes and insects of the ground to eat away at the flesh and decay until all that's left is bone. While natural, I do not employ this method because the dirt has a way of staining the bone a dirty, dull yellow, and algae growth is frequently a problem. Furthermore, teeth are frequently lost in the dirt. Other people use a months-long cold or warm water maceration method, where the natural bacteria in water eat the flesh from the bones. I don't like this method because it takes forever, smells horrible, and it's easy to forget to change out the water as it gets dirty. Bones that soak too long in putrid water can become infused with the stench forever. Yuck! But by and large, the best of all is the dermestid beetles method. Unfortunately, most hobbyists do not have the space or resources to keep a colony of these specialized critters, as they are quite demanding and can be very stinky. If you are fortunate enough to have the space and funds to appropriately raise a colony of these amazing bugs yourself, I highly reccomend it!