Skull Cleaning Methods
Most of the time a skull collector will have to clean a specimen- not all skulls are found thoroughly cleaned of flesh, so more often that not it is necessary to apply an efficient teqhnique that will result in a nice clean skull. Here I have listed some of the methods I have used in the past. They all work, but preparation time varies according to the technique used. In some cases climate plays a strong role in the preparation time of a skull.
Maggots are the obvious choice. Most corpses found above ground tend to already have there own larvae inhabitants so why not let nature take its course? Even if the carcass appears to be a maggot free zone it doesn't take much to provide the right environment to attract flies to your find:
You may chose to skin your specimen first. Place your carcass or animal head in a plastic bag, leave a small enough gap in the opening of the bag to allow flies enter, but don't leave it so wide that the carcass will dry out. Leave the slightly opened bag in an area where scavanging animals cannot access it- I usually put mine in my shed. The plastic bag will retain moisture and warmth which are important factors for the survival of fly larvae. The warmer the weather, the quicker the technique will work. The smell will be intense, but the results are generally good. Unfortunately you may have to sift through a large amount of stinking goo to retrieve any teeth that may have dislodged during the process. Also you might discover that you have largely increased the local fy population- you do need understanding neighbours if you wish to use this method. The skull/bones will need a good wash in warm soapy water after retrieval.
N.B 1) this method is not suitable for mummified specimens. 2) this method is unlikely to work in the months of winter
For this method it will be necessary to skin your animal head and remove the eyeballs. Place in a good sized pan filled with water and bring to the boil. Leave to simmer until the meat drops off the bone (carrots, turnip and potatoes can be added, but eat it at your own risk). On completion the specimen will be HOT, do not be tempted to cool it with cold water as this will crack the teeth, it may also crack the bone in some cases. This method is not recommended for the preparation of young animal skulls as the boiling water has a tendancy to crack the teeth. In baby animals the hot water may distort the shape of the skull fragments.
N.B The stench of boiled rotten flesh isn't very nice to those not accostomed to the smell
There are two types of maceration that can be used to clean animal skulls. The first is cold water maceration:
Fill a good sized container with cold water and add your skinned specimen. This method will take some time, it may not work at all during the Winter months.
Warm water maceration is much faster than cold water maceration. For warm water maceration you will need a good sized container and an aquarium heater. Fill you container with cold water and add the aquarium heater which should be set at 35 degrees C. Add your skinned specimen. The heat of the aquarium heater will encourage bacteria to reproduce, it is this bacteria that will break down the soft tissue of your specimen. This method should not take more than a week to complete.
N.B Warm water maceration is not recommended for the preparation of duck or goose skulls. If you are preparing other bird specimens using warm water maceration and wish to retain the beak sheath you will find that between 1-3 days it will slide of quite easily. Don't leave the beak sheath attached through the geration of the process as the bacteria will destroy it. The same applies to claw and hoof sheaths.
Burrying a specimen is a good way to clean it if you don't mind waiting. Unfortunately teeth can often go astray, also, if your memory is anything like mine, you might forget the exact location in which you burried your specimen. My answer to these problems is 'isolate' your specimen. For this you will need a container slightly larger than your specimen, the container will need drainage holes in the bottom. Cover the bottom with a layer of soil then place your specimen on top. Throw in a good handful of worms then cover the lot with soil and water it. You may wish to place a lid on the top to keep scavangers out- make sure you put some air holes in the top about half a centimetre in diameter, this will allow air to circulate within the container and mold is less likely to form on the soils surface. Water your corpse on a regular basis, this will keep the carcass damp and the worms active (do not waterlog your specimen). You will have to dig out your corpse every month or so to see how it is doing. The advantage of this method is, you can keep your 'isolated' burial on your windowsill like any other conventional window box and your neighbours won't suspect a thing.
N.B 1) This method is not likely to work for mummified specimens. Try soaking them in hot water first. 2) For fresh specimens, try leaving the carcass to 'air' in the sun for an hour or so before burying it, this will give flies a chance to lay there eggs on it, which may speed up the decaying process during burial.
There are several ways to deal with mummified flesh on a corpse. One of the most efficient ways is using dermestid beetles. Many collectors have a colony of dermestid beetles just for this purpose, unfortunately this is a method I have yet to try. For more information on Dermestid beetles see this website
For those of us who do not have dermestid beetles, mummified flesh can be a nightmare. I have found that any one of the above methods can be used on mummified flesh providing the specimen has been soaked for 1-3 hours in hot (but not boiling) water before hand. The most efficient way (dermestids aside) is warm water maceration. Any of the other methods (with the exception of maggots) are just as effective, unfortunately they take much longer.
Once your skull has been completely defleshed, you may wish to consider degreasing it. Often defleshing methods aren't enough to break down the fat content with the bone. After a period of time the grease will begin to rise to the surface of your skull giving it a yellow or brown appearance that feels greasy to the touch. Once they get to the state the problem can be difficult to rectify. Prevention is always better than cure.
There are two ways that skull collectors recommend, the first is ammonia. Household ammonia can be purchased fairly cheaply at most hardware shops and supermarkets. Soaking your skull in a tub of ammonia for a week or two can often help draw out the grease. Personally I have found this method of degreasing to be inaffected. The length of time you leave the skull in ammonia depends on the size of the skull. Something the size of a mouse probably won't need more than a few days, a sheep skull may take a week or two.
The second method of degreasing is using a biological washing powder. These contain natural enzymes that will help break down the grease. The one recommended by most British skull collectors is Biotex prewash powder, because this has doesn't have lots of added chemicals that may be detrimental to your skull. Biotex is easy to use, simply add a cup full (more or less, depending on water volume versus skull size) to a tub with enough water to cover the skull. I find a cup full in a bucket with enough water to cover the entire skull is ample to degrease a sheep skull. Cold water can be used providing it is kept at room temperature, but I find that applying an aquarium heater set at around 32 degrees Centigrade is far more affective. How long you leave it depends very much on the size of the skull. A sheep skull may take between 2-3 weeks, but check the skull regularly, smaller skulls will take less time to degrease. Be careful not to leave a skull in to long as the bone may start to become chalky. Also the Biotex may turn the water into a snot-like texture, in which case the solution will need to be changed if the skull is not yet ready. When the degreasing process is complete rinse your skull thoroughly. If your skull isn't rinsed properly you may be left with a white podwery residue on the surface of the bone once it has dried.
It may be tempting to use household bleach to whiten a skull but there are two problems with this 1) It doesn't work 2)It damages your skull. You may not see any initial damage to your skull when you have used household bleach on it, but bleach is long acting on bone. After a period of time you will notice that the skull begins to look old and flaky. After a few years it will start looking more like an archaeological discard, than a museum quality skull specimen. So how do museums get that Daz-white look? They use hydrogen perioxide. This stuff can be purchased at your local chemists. It is the stuff people use to bleach their hair. It is usually available in solutions of something between 4% and 9%. These solutions can be used neat on your skulls. However I would recommend only using the 9% solution on larger skulls. There are stronger solutions available on the market which are only vailable in large quantities. It may prove cheaper to purchase in larger quantities for larger skulls, but these strengths will need to be diluted. Hydrogen Perioxide can burn flesh, so wear protective gloves when using the stuff. The weaker solution may only leave a white residue on your fingers, but stronger solutions (especially the industrial strengths) will definately burn. You have been warned. Once your skull has been successfully whitened, remove it from the hydrogen peroxide and rinse thoroughly
When your skull is nice and clean, but dripping wet you might be tempted to 'speed' dry it by putting it on a radiator, close to the fire etc. Don't! When the teeth of skulls dry out too quickly they have a tendancy to crack. Towel dry your specimen and leave it to dry naturally for at least 24 hours. With young animals you will need to leave it longer. The bones of young animals are much more porous than that of adults. The porosity of the bone behaves like a sponge and absorbs the water. Even if the skull does look dry, it may only be surface dry. Make sure it's thoroughly dried out before you start reapplying any loose teeth, or repairing any dislodged fragments.