Want to clean and whiten bones or a skull? The first step is to get the soft tissue off the bone.
This is actually one of the trickiest and most time-consuming steps of cleaning bones. If you don’t do it correctly, you can end up permanently damaging the bones, losing bones (especially small bones like finger bones or vertebrae), or you might have issues with scavengers carrying away your bones!
There are six different methods to clean tissue off of bones before you whiten them. The choice depends on factors like:
- The size of the specimen
- How much tissue is remaining
- How much time you have
- Removing Brains
- Hidden Tissue
- What about boiling bones to remove tissue?
Methods for Removing Tissue from Bones
Best for: Large bones and skulls with lots of tissue remaining; rotting carcasses
Dirt might seem like there’s nothing going on with it, but there’s actually a party of bacteria and other microorganisms in dirt.
When you bury a carcass in dirt, these microorganisms will eat the tissue around the bones. Some worms and bugs might help clean off the tissue too. They won’t eat the bones though, so they will be safe.
The great thing about this is that bacteria can get into all those tiny little crevices. That means you won’t have to do things like “scramble” the brain to remove it. (Gross!)
How Long Does It Take?
It depends on how big your specimen is, how much tissue is on it, the temperature, and even the type of dirt (some dirt is much more active than other types).
You might get lucky and only have to wait a few weeks before the tissue is all gone. Or, it could take up to 3 months for a large animal carcass to fully decompose.
One potential issue is that scavengers can dig up bones that you buried. Even worms/insects can move around bones a lot in the dirt.
To keep your bones safe and make them easier to find when you dig them up, I’d recommend that you put the carcass in a wire mesh (for larger bones) or a muslin sack (for smaller bones).
Note that the dirt might stain the bones a bit, but this can be removed later during the whitening process. It’s best not to bury antlers since you probably want to keep these their natural color (more on preserving antlers and antlered skulls here).
Method 2: Insects/Leave Out in the Open
Best For: All types and sizes of bones; rotting carcasses
Professional taxidermists use insects like dermestid beetles to remove tissue from bones. You probably won’t want to raise these yourself, but you can still harness the tissue-cleaning power of insects.
Leave the corpse or bones outdoors, preferably over an ant hill if you can find one. The insects will do a great job of eating tissue out of those hard-to-reach places on bones and skulls.
How Long With It Take?
If you are able to put the carcass next to an ant colony, then it might be completely cleaned within 1-2 weeks. Otherwise, expect this method of cleaning tissue off of bones to take at least a month.
Like with burying bones, you can expect scavengers to carry away the bones. You’ll need to put the bones in a wire cage so insects can still get to them but animals cannot.
Method 3: Corpse in a Box Technique
Best For: Small animals with lots of tissue on them
Small bones easily get lost in the dirt when you bury them. And, if you try to leave them out in the open, you will likely lose their tiny bones.
One solution is to use the “corpse in a box” method. You simply:
- Get a box that has a lid. Old ice cream containers work well.
- Poke some holes in the box.
- Put the corspe in the box.
- Keep the box outside somewhere covered so it won’t get flooded by rain.
Insects will enter the box through the holes and lay eggs. The eggs will hatch into maggots, who will happily eat the tissue off of the carcass.
How Long Will It Take?
Expect it to take at least 1 month to get completely clean bones. If the carcass only had a bit of tissue on it and there are lots of flies that get at the bones, then it might be done faster.
The only main issue is that insects won’t eat fur of feathers off of the carcass. You’ll end up with a box full of tiny bones and have to carefully separate them from the fur/feathers. This is a pain — but this is an issue with small animal bones regardless of the method you use for cleaning tissue.
Method 4: Maceration (Soaking)
Best For: Bones without a lot of tissue left on them
Soaking bones in water will soften the tissue and allow you to scrape it off. There are also lots of microorganisms in the water which will eat away at the tissue. So, you end up with very clean bones. This method is especially good at getting rid of tissue in tiny crevices in skulls.
Brains are pretty rubbery and won’t break down like other soft tissue will. So, you should remove the brain before macerating skulls. This is really nasty. You have to take a wire to scramble the brain and then shoot it out with a hose. Ideally, you wear goggles and waterproof coveralls so you don’t end up with brain all over you.
How Long Will It Take?
It takes a very long time to get the tissue off with maceration. Expect weeks or even months of soaking!
You can speed up the process by adding biological cleaning powders/enzyme stain removing powder such as Biotex (which you can buy here) These cleaners contain enzymes which will break down the soft tissue. However, there is a lot of controversy amongst professional taxidermists as to whether this damages bone or not.
The maceration method is VERY disgusting. You’ll have a bucket filled with stinky tissue. You’ll have to dump/change the water at least once daily.
I don’t have a backyard, but I did macerate small animal carcasses in jars in my bathroom. I puked when I opened the jars to change the water, the smell was that bad. And the smell lingered for a while. I apologize to my family!
Also, be careful that you don’t lose bones or teeth when dumping the water. Ideally, you dump the water into the grass so you can retrieve any bones that come loose. Or, dump the water through a sieve.
Method 5: Simmering
Best For: Fresh carcasses when you are in a hurry
If you have a fresh carcass with all of its tissues on it, then you can simmer it to remove the tissue. The hot water does wonders and loosening tissue so you can scrape it away.
However, for reasons we’ll talk about below, you shouldn’t let the water get to boiling. Make sure that you keep the temperature down low and monitor the process.
How Long Will It Take?
You’ll want to put the carcass or skull into the water and then bring it to a simmer. After about 10-15 minutes, remove the carcass and scrape away as much tissue as you can. You’ll also need to scramble and remove the brain at this point. Some people leave it simmering for up to an hour before scraping.
After scraping away the tissue, dump the water (being careful that you don’t lose any bones in the process) and simmer again.
Note that simmering isn’t going to do a great job of getting rid of hidden tissue. Ideally, you macerate the bones or leave them outside for microbes to clean before going on to the whitening step.
Try to remove as much hide and tissue as you can before simmering. This will prevent the water from getting too gross, and then that grossness getting absorbed into the bone.
A lot of people put additives like OxiClean into the simmering water. This supposedly helps break down tissue and also get fat out of the bones. A lot of people swear by it. But a lot of other people also say that OxiClean will destroy bones, causing them to literally turn to mush. It seems to be okay on deer skulls, but probably not okay on fragile bones. Try this at your own risk! Or, better yet, be patient and just bury the bones to get the tissues off. It will take longer but the results will be much better.
Method 6: Steaming
Best For: Smaller bones with lots of tissue remaining
While I haven’t tried this personally, Jake of Jake’s Bones uses a baby bottle sterilizer for cleaning tissue from bones. Basically you steam the bones inside the sterilizer.
The steam will loosen tissue quickly. Since the bones aren’t floating in tissue-filled hot water, the fat won’t absorb into the bones. Nor will the heat damage the bones. Jake warns that it will smell disgusting!
Removing Brains from Skulls
This is gross. Really gross. I’m still pretty squeamish, so I will avoid doing this at all costs. With the burial, insect, and “corpse in a box” methods, you can leave the brain in the skull. Microbes will eat it away for you.
However, if you want to use simmering or maceration to remove tissue, you’ll have to remove the brain. Brains are really fatty and rubbery, so won’t come out so easily on their own.
Here’s how to remove a brain from a skull:
- Soak the skull to get the brain tissue soft (or give the skull a quick simmer)
- Take a wire/coat hanger and start jamming it into the skull. The goal is to “scramble” the brains. This is something the ancient Egyptians mastered thousands of years ago. 😉
- Get a power washer and blast into the back of the skull. Brains will shoot out of the nose. WEAR GOGGLES unless you don’t mind getting pieces of brain in your eyes.
- Or use a saw to cut off part of the back of the skull and scoop out the brains. Some skulls (like deer skulls) sit better on their mount when the back is flat anyway.
Hidden Tissue in Skulls
Be warned that there is a lot of tissue hiding in animal skulls – especially big animals. For example, there are often giant nerve endings inside teeth.
You will also have nerves going through foramina in skulls. Foramina are holes where the nerves go from the brain to the face.
To remove this tissue, you may need to:
- Carefully remove front teeth with pliers. Wash/poke out nerve endings. Make sure to reinsert the teeth while the skull is still wet. Otherwise the bone shrinkage might make it impossible to get teeth back in. Ideally, you remove morals too but these are really difficult to get out.
- Use wire to poke tissue out of foramina: This only works to a point. You’ll be able to get some of the nerve tissue out but probably not all. One more reason microbes do the best job of cleaning bones!
What about Boiling Bones to Clean Them?
In many forums and websites, people recommend boiling bones to remove the tissue. Yes, this works very well. It only takes about 2 hours of boiling for most of the tissue to fall right off.
But boiling is a terrible way of cleaning bones. It can turn them yellow, make them start rotting, and damage fragile bones.
Here’s why you should NEVER clean bones with boiling.
Boiling Traps Fat in Bones
Our bones are very much alive. They have their own blood vessels and nerves. Bones are also little “factories” in that they produce blood cells in their marrow. Guess what marrow contains? Lots of fat!
If you boil bones, the heat will seal the fat into the bones. They will turn a gross shiny yellow color.
Not only does this look terrible, but the fat trapped inside can start to rot. As it deteriorates, it can destroy the solid bone tissue. The bones will end up smell really bad. And, over time, the bone can crack.
*It is possible to remove trapped fat with a process called degreasing, but it’s a major pain and takes forever. The pig skull above took MONTHS to degrease! More on degreasing in my book.
Fat from Tissues Get in the Bone Too
Not only do the bones themselves contain a lot of fat, but there is tons of fat in the hide and tissues of an animal. Brains, for example, are about 29% fat. The human brain is even fattier at about 60% fat.
When preparing bones for cleaning, you should remove the skin, brain (which is a pretty gross process), and as much tissue as possible.
If you skip this step and boil an entire corpse, he fat from tissues will get in the water. This fat then gets absorbed into the bone where it becomes trapped. The bones will end up even more fatty and gross.
Boiling Traps Tissue in Skulls
As bone enthusiasts know, skulls have so many little nooks and crannies. When the animal is alive, these nooks are filled with nerves, blood vessels, and other tissues.
If you boil a skull, all of these tissues will get trapped in the nooks. It is really difficult to remove the tissue afterwards!
It is especially bad in the foramina. A foramen (plural foramina) is a little hole in bones where nerves or blood vessels go through.
You can try to remove the tissue by poking a wire inside the foramina. However, this is actually hard to do. Instead of removing the tissue, the bits of nerve and blood vessels often just get pushed further up inside.
Boiling Damages Fragile Bones
Some bones are particularly fragile and won’t withstand boiling well. One example is juvenile animals. Their skull bones haven’t completely fused together yet.
Boiling will dissolve the connective tissue holding the skull together and ruin your beautiful skull.
After the tissue has been removed, you’ll need to get the grease out of the bones and whiten them. In my ebook, you can read all about how to do it, plus instructions for horns, antlers, bird skulls, fragile bones, and more.
Get the book here. It’s only $4.99 and will teach you how to clean bones without any special equipment.
“Deer bones (https://www.flickr.com/photos/jive667/5570141604/)” (CC BY-ND 2.0) by jive667
“Skull: Head-on” (CC BY-NC 2.0) by Travis S.
“Mini Facehugger” (CC BY-NC 2.0) by Travis S.