Preserving bones, whether from a found animal skull or a specimen you’ve cleaned yourself, requires removing organic material, pulling out trapped grease, whitening without damage, and sealing the surface so it lasts for years. Skip any of these steps and you’ll end up with a specimen that yellows, smells, or slowly crumbles. Here’s how to do each stage properly.
Remove All Soft Tissue First
Before any preservation can begin, the bone needs to be completely free of flesh, cartilage, and connective tissue. The three most common methods are maceration (soaking in warm water), dermestid beetles, and simmering. Each has tradeoffs.
Maceration is the simplest approach. Submerge the bone in a bucket of warm water (not hot) and let bacteria break down the soft tissue over one to three weeks, changing the water every few days. It smells terrible but produces clean results without heat damage. Adding a small amount of dish soap helps lift grease during this stage. Dermestid beetles, used by many taxidermists and museums, eat soft tissue while leaving bone intact. They work well for skulls where you want to keep delicate nasal structures in place. Simmering in water (never a full boil) speeds things up to a few hours but risks cracking, warping, or making the bone chalky if the temperature gets too high. Actual boiling denatures the proteins in bone and should always be avoided.
Degrease Thoroughly
This is the step most beginners skip, and it’s the reason so many preserved skulls develop ugly yellow or brown stains months later. Bone, especially from bears, pigs, and marine mammals, contains a surprising amount of lipid (fat) locked inside its porous structure. If you don’t pull it out, it will seep to the surface indefinitely.
The most accessible degreasing method is soaking the bone in warm water with a grease-cutting dish detergent for several weeks. Keep the water around 100°F to 110°F if possible (a simple aquarium heater works) and change the solution when it turns cloudy or develops an oily film. Small, lean bones from deer or rabbits may only need a week or two. Dense, fatty bones from larger animals can take two months or more.
For faster or more thorough results, chemical solvents are effective. A 1:1 mixture of ethanol and acetone, soaked for 24 hours, pulls lipids efficiently from cancellous (spongy) bone. Another approach uses a gradient method: soaking in progressively stronger alcohol concentrations, starting at 50% for two hours, then 75% for two hours, then 96% for two hours, and finishing with 99% ethanol for 18 hours. A combination of 99% ethanol for 20 hours followed by a detergent solution for 4 hours also works well. These solvent methods are particularly useful for porous bones where water-based degreasing stalls out. Work in a well-ventilated area and keep solvents away from open flame.
You’ll know degreasing is complete when the bone dries uniformly without any greasy sheen or translucent patches.
Whiten With Hydrogen Peroxide
Once a bone is clean and fully degreased, whitening gives it the classic display-ready appearance. Hydrogen peroxide is the standard choice. Use a 3% to 6% solution, which you can buy as standard drugstore peroxide (3%) or mix from salon-grade developer. Products labeled “20 volume” are roughly 6% hydrogen peroxide, “30 volume” is about 9%, and “40 volume” is around 12%.
Stick to the 3% to 6% range. Higher concentrations speed things up but risk breaking down the bone tissue itself, leaving it chalky and brittle. Submerge the bone or, for mounted skulls, apply a paste of peroxide mixed with baking soda or magnesium carbonate directly to the surface. Check every few hours. Some slight off-white color is normal and actually looks more natural than a perfectly bleached bone. Severe bleaching weakens the specimen, so stop before it goes pure white.
Never use household chlorine bleach. It penetrates the bone structure, continues to break down collagen over time, and causes flaking and crumbling that can’t be reversed.
Seal and Strengthen the Surface
Unsealed bone is porous and will absorb moisture, dust, and oils from handling. A sealant protects the surface and can consolidate fragile or weathered specimens.
The museum standard for bone and fossil preservation is an acrylic resin called Paraloid B-72, dissolved in acetone. It’s reversible (you can remove it later with solvent), doesn’t yellow over time, and penetrates deeply into porous material. For consolidating fragile bone, a dilute solution of about 5% (roughly 25 grams of resin per 500 ml of acetone) soaks in without leaving a glossy surface. For general sealing, a 10% solution (1 part resin to 9 parts acetone by weight) gives good penetration and durability. Apply multiple thin coats rather than one heavy one, allowing each to dry before adding the next. For gluing broken pieces, a 50% solution acts as a strong adhesive.
If museum-grade supplies aren’t accessible, a clear matte acrylic spray from a hardware store provides basic protection, though it won’t penetrate as deeply and may yellow slightly over decades.
Store Bones in Stable Conditions
The biggest threats to preserved bone in storage are humidity swings, heat, and direct sunlight. Bone is a composite of mineral and protein (collagen). High humidity encourages mold growth, while very dry conditions cause the collagen to shrink and the bone to crack. Rapid fluctuations between the two are worse than either extreme alone.
Museum collections keep bone specimens at 50°F to 59°F with 35% to 55% relative humidity. You don’t need a climate-controlled vault at home, but aim for a room that stays reasonably cool and doesn’t experience wild temperature or humidity swings: an interior closet or cabinet rather than an attic, garage, or basement. Keep specimens out of direct sunlight, which bleaches surfaces unevenly and heats the bone. If you’re storing bones in boxes, use acid-free tissue paper or polyethylene foam as padding, not newspaper or cotton batting that can trap moisture or transfer acids.
For display pieces, a glass case or dome reduces dust buildup and buffers against short-term humidity changes. Handle specimens with clean, dry hands or cotton gloves, since skin oils will absorb into unsealed bone and create stains over time.
Special Considerations for Found or Old Bones
Bones found outdoors may already be partially weathered, with surface flaking or a powdery texture. These benefit from consolidation before any cleaning. Applying a dilute Paraloid B-72 solution (5% or less) stabilizes the surface enough to handle and clean it without losing fragments. Let it dry completely, then proceed with gentle cleaning using soft brushes and water.
If you find bones you suspect are human, don’t collect them. In most U.S. states, possession of human remains is tightly regulated. Federal law under NAGPRA (the Native American Graves Protection and Repatriation Act) governs Native American remains specifically, and state statutes vary widely on other human remains. Washington state law, for example, restricts possession to the person with legal authority over disposition of the deceased. Contact local law enforcement or a coroner’s office if you encounter remains that appear human.
Animal bones are generally legal to collect and preserve in the United States, with notable exceptions. Migratory birds are protected under the Migratory Bird Treaty Act, making it illegal to possess their bones, feathers, or nests without a permit. Marine mammals, bald eagles, golden eagles, and endangered species all have their own federal protections. When in doubt, check with your state’s fish and wildlife agency before keeping a specimen.