In terms of cleaning skulls/bones, whitening (also wrongly called bleaching) is the process of sterilizing or turning bone white usually via hydrogen peroxide.

What Materials are Needed to Whiten Bones?

1. Flesh-free bones (See Maceration 101 if your bones aren’t flesh-free yet)

2. Liquid or Cream Hydrogen Peroxide

3. Optional (works well with Creme Peroxide)- Basic White Powder

4. Gloves (If working with high percentage peroxide)

5. NO Chlorine Bleach

6. Recommended: Mesh Bags

Why/When to Whiten Bones

Whitening is not a necessary step when cleaning bones, but it does sanitize them and give them a nice clean-looking white finish. If you prefer the natural color of bone but still would like to sanitize them, you can put them in low percentage peroxide for an hour or less.

Even with whitening, you will never end up with  perfectly white bones if they are not properly degreased. You can read Degreasing 101 if your skull or bones have any yellow, orange, dark, or translucent areas

How Long Does Whitening Take?

The period of time that you should leave your bones in peroxide depends entirely on how white you want them and what percentage of peroxide you’re using. If you’re using higher strength peroxide you can get a very white skull in an hour or two. If you’re using 3% from the generic brown bottles you may want to leave your bones in for a day or two. Overall, whitening is probably the shortest step of Processing Bones and you should be able to achieve the degree of whiteness you want in only a few days as long as the skull was properly cleaned beforehand and does not have any staining (such as from soil, but sometimes even soil staining comes out with peroxide)

Whitening Method 1: Liquid Hydrogen Peroxide

By far the most common method of whitening bones due to its usual occurrence in homes, regular hydrogen peroxide from the brown bottle under your sink! At only $1 for a quart size bottle, this 3% peroxide will get the job done for cheap if you’re working on something small. Can be used straight or diluted (though I recommend straight when using 3%), simply cover the skull or bones in the peroxide and wait until it becomes as white as you want it. If your skull is dirty or has a lot of bacteria in/on it it may begin to bubble, but it’s completely fine if you don’t see any bubbles- it doesn’t mean it’s not working. I recommend using Mesh Bags to make sure you don’t lose any teeth or small bones that may float in the peroxide. These bags come with a lifetime warranty.

The next step up is higher percentage liquid peroxide. Here in the United States the absolute highest percentage peroxide that a citizen can get is 50% I believe. This is EXTREMELY strong. Like, bomb-making strong (hence why it’s so hard to get). Peroxide is an oxidizer, and strong peroxide will react very very violently with metals. Even the smallest bullet fragment can make 50% peroxide extremely hot and uncontrollable and can result in a very serious fire. The next step down from 50% is 27-35%, which is much easier to get. This can be bought at most pool supply stores (I get a gallon of 27% called “Aqua Silk” from Ace Hardware) or online. It goes by many names, so go to a pool store and ask for “chlorine-free shock”. Make sure to read the ingredients label! You ONLY want peroxide in there. Any other chemicals or stabilizers may damage the bones.

When using strong peroxide, you may dilute it or use it straight. Anything over 12% is pretty strong, so I personally always dilute mine. I don’t have a set percentage or ratio that I use to dilute it, I just pour some peroxide in whatever container I’m using and then fill the rest up with water. Strong peroxide carries some safety hazards! You absolutely want to wear Gloves when working with strong peroxide, as it will burn your skin and turn it white for a few hours if any gets on you. I’ve gotten 27% peroxide on me many times, and it burns quite a bit. Best thing I’ve found to relieve the burn is to run very hot water over the affected area. The heat will speed up the reaction and stop it from burning you any further. You absolutely do not want any to get into your eyes! I have read strong peroxide can cause instant blindness, so make sure to wear proper eye protection when working.

Whitening Method 2: Creme Developer Peroxide

This is the method that a lot of old school taxidermists use on large skulls. I personally have not used this method, but many of my colleagues have, so I’m including it as an option. The main ingredient you’ll need is Creme Developer for your hair. This can be bought online or at beauty supply places such as Sally’s Beauty Supply. This developer comes in “volumes”. This is not the same as percentages of peroxide. Here’s a conversion chart so you know what percentage of hydrogen peroxide is in each volume of developer

Volume of Developer contains this percentage of hydrogen peroxide

10 volume or V10

3%

20 volume or V20 

6%

30 volume or V30 

9%

40 volume or V40 

12%

You may use any volume, as even the 40 volume (12% peroxide) isn’t strong enough to cause any damage to bones. Still wear gloves and take precautions to protect your eyes though! The application is pretty easy, either soak your skull/bones in the developer, or apply it to the outside of the skull. If you want to make a whitening “paste” to apply to the outside, you can mix developer with some Basic White Powder until you get the consistency you want. Let sit until dry, pop/wash off, and you should be left with a white skull! The advantage of this method is that you don’t have to use very much peroxide to get your skull nice and white, but the con is that only the outside of the skull will be white, not the internal structures. I’m not well-versed in this method, so I’m not sure if diluting is a good idea for creme developer. The reason I do not use developer is because it is not pure peroxide. There are several additives (Cetearyl Alcohol, Ceteareth-20, Stearic Acid, Cetyl Alcohol, and Phosphoric Acid) to act as stabilizers for your hair and to make it a creme instead of normal liquid peroxide. I’ve never heard of the stabilizers causing any damage to bones, but I personally just prefer to use peroxide without any additives (excluding water).

Whitening Method 3: Bleach

No. This method doesn’t exist. NEVER USE CHLORINE BLEACH ON BONES. “Why not?”, you might ask, well here’s why:

Chlorine Bleach eats bone. It is not stoppable, and is not reversible. Once a skull has been soaked in bleach, it will continue to deteriorate until it crumbles/flakes away. This may happen in as soon as a few days, or it may take decades. Most amateur processors will bleach bones at least once, as whitening is often wrongly called “bleaching”. I myself bleached my first skull, but it was highly highly diluted (cap full to around 2 gallons of water), and it was only in there for a few hours before I researched and found out that that was NOT the correct way to whiten bones. Still, eventually my skull will likely start showing signs or deterioration.

How to tell if a skull has been bleached:

Tiny white pieces of bone will begin flaking off when you handle the skull

It’ll be very fragile. Any thin section is much more likely to break and crumble than on a properly processed skull

It’ll be very porous. This is from the top layer of bone being eaten away, exposing the more porous layer underneath.

How to Prevent Bleach Damage:

Don’t use chlorine bleach on bones. Very simple. 

Tips and Tricks for Whitening

1. Heat! Heat and sunlight will speed up the reaction of peroxide (hence why it comes in dark bottles and tells you to keep them in a dark, cool place). If you’re in a rush to get some bones extra white in limited time, try heating up your peroxide while your skull is in it. You do not want to boil it. Boiling causes bone damage. There’s no set temperature to use, but I’ve found that the same temperature we used in the Degreasing Guide works quite well. I’ve used the same Bucket Heater I use for Macerating and Degreasing to test heating peroxide, and it worked just as well as expected. This is the method that most taxidermists use, but where they go wrong is boiling it. The pros of this method: It gets stuff really white, really fast. The con is: your peroxide will mostly be dead after you’re done. Boiling or freezing peroxide will deactivate it, so keep the temps between those if you want to be able to reuse your peroxide as much as possible.

2. Wash off with hot water! Similar to tip 1, but it saves your peroxide. Soak the skull in cold (room temp) peroxide for a day or two, and then dunk the skull in a bucket of really hot water (not boiling…. just as hot as your tap will get). The heat will activate any peroxide that is still in the bones, as well as wash off any residue that might still be on the bones.

3. Sunlight! You’ve probably heard of sun bleaching, well that works on bones too! After the peroxide bath, set your skull out in the sun. The heat/UV rays from the sun will activate the peroxide and will get your skull a bit whiter than it would be otherwise.

What Do I Do Now?

Enjoy your properly clean skull! You shouldn’t need to do anything else! Occasionally some stubborn grease will start surfacing after some months/years, but if that happens just repeat the Degreasing Steps. 

****Any skulls we get in that have already been pre-bleached, we reinforce with a museum grade sealer to prevent further damage to the bone. We here at Beautifully Strange Oddities have never and will never use chlorine bleach in any of our processes when processing our own animals or bones.****