About Bone Building: Animal Skeleton/Bones Cleaning and Assembly

Animal skeleton/bones cleaning and assembly. Skeleton articulation, or bone building as I call it, is the process of converting a dead animal into a completely cleaned and articulated skeleton. There are many different cleaning methods ranging from letting the carcass rot above ground, to soaking the bones in various nasty chemicals. Each method of cleaning has its advantages, disadvantages, and proponents who will strongly favor one method over another. For school use, some methods work much better than others. After all flesh is gone, the bones often need to be further prepared by degreasing and whitening. This gives the bones a long term clean white look as opposed to being, greasy, and dirty looking as some prepared skeletons look after a bit of time.

Then the bones are assembled - or articulated. This process is much like assembling a full-scale model with bones being fastened to other bones by various means including glues, pins, wires and steel rods. Usually, the skeletons are solidly fastened together but options can include skeletons that are made to bend at the joints or skeletons that come apart so they can go back into a box after assembly.

Are the bone going to be a classroom project good for a grade? Or will they be a museum quality mount good for 100 years? The difference being how much care gets put into preparing the skeleton and how securely the bones are fastened together.

FOR THOSE WHO WANT TO PUT A SKELETON TOGETHER, BUT WANT TO KNOW WHAT THEY'RE GETTING INTO FIRST

Who can do a skeleton project?
Skeleton articulation is sometimes thought to be only something done in museums by trained professionals. In truth, there are very few skeletons that get articulated in museums, and even fewer museum professionals that articulate skeletons. Most new skeletons in museums get put together by enthusiastic volunteers, or as paid projects by museum design firms. At one time museums very well may have had preparators on staff articulating skeletons. People who articulate skeletons these days range from students in schools to enthusiasts at home, to taxidermists in shops to groups in nature centers - even next door neighbors. Many of the best skeletons are being done by non-paid enthusiasts who have all the time in the world to get it right.

What kind of animal skeleton can be used?
Anything with bones inside of it - but the major prerequisite is for it to be dead first and cleaned of soft tissue second. The size of the animal is going to be a determining factor. Small animals come with even smaller bones and at some point, the bones are too tiny for most mortals to be patient enough to get back together. Think foot bones the size of pinheads and ribs the diameter of the pins - like on a hamster or weasel. Animals need to be at least the size of a house cat or chicken to easily be feasible to reassemble their skeleton when the bones are totally cleaned and disarticulated. Smaller animals can be converted to skeletons but these are generally done as ligamentary skeletons (see the oxidation page as one method of doing this) in which the flesh and soft stuff are mostly removed, but the ligaments and cartilage are left in place to hold the bones together. It is more a process of bone cleaning than bone building. The skeletons are posed and dried and even the tiniest skeletons can be prepared this way.

How do you clean the bones?
There are many ways of removing the soft tissue from the bones, all of which have advantages and disadvantages. In spite of claims to the contrary, any of the methods can work to produce high-quality skeletons. These range from composting, to rotting (above or below the ground), to macerating (rotting in fresh or salt water), to simmering, to using chemicals, to using insect colonies. Some of the methods are faster than others. Some are too stinky to do inside. Some take careful watching. Some carry more risk of bone damage than others. What method gets used depends on the animal, the size, the maturity (of the animal - maybe of you too), your circumstances (as in do you live in a city apartment or do you have a farm in the country for example), and what your time frame is.

How long does it take to clean the bones?
Times to get the bones clean of flesh can range from overnight by simmering, to several months in cold water maceration, to several years if they were buried deeply. Insects can clean bones within a week in the right conditions and warm water maceration in a container of heated water may take a few weeks. Once the bones are clean of flesh on the outside, depending on how that was done, the inside still needs to be cleaned. Fresh bone is full of fats in the form of oil or marrow, as well as blood, fluids, veins, arteries, and other cellular tissue. Getting that out without doing destructive things to the mineral part of the bone is the big challenge. Some cleaning methods such as composting or long term water maceration can remove the oils at the same time as the flesh on the outside, but many other methods such as simmering or using beetles to clean, leave the inside of the bones too oily to move on to the next steps. Getting the inside clean is called degreasing the bones. It can be done naturally with microbes in the soil or the water, or it can be done by soaking the bones in solvents or detergents. The time factor depends on how oily the bones are, how large the bones are, and what type of fats are in the bones. Small and not very oily animals may be degreased within a week or two and other bones may need to be processed for multiple rounds of a week each round, or with a combination of detergents, heat, or solvents. Some bones, depending on the method used for degreasing, can take months of soaking. They are clean enough when no more oils leach out. After the bones are degreased, most people want them whiter and brighter. They can be bleached in the sun if one has the time and a place to do this or they can be bleached artificially with chemicals (usually hydrogen peroxide). Most bones can be whitened enough in a matter of days. Then the bones are dried for usually a few days and only then are you are ready to assemble.

What about small skeletons?
Oh yes, if the animal is too small to rebuild it bone by bone, it can be prepared as a ligamentary skeleton. This is usually done by using captive colonies of insects (usually dermestid beetle larvae) to eat the flesh off. This requires having an active hungry colony of beetle babies. A big hungry colony can clean something in days, or a not so big colony can take weeks to get bones clean. Colonies are often kept in aquarium tanks or old chest freezers, usually not in the house, however, due to odors. Otherwise, there are various methods of using a combination of chemicals, maceration and boiling to clean the flesh from a small animal. A time factor can vary from a week to a couple months of soaking and cleaning - usually followed by more time in degreasing and bleaching agents, and a final round in bleaching chemicals. Some skeleton projects can be done on your kitchen countertop or table without too much objection, and others are a garage or outside only projects. After the cleaning and degreasing, the skeleton gets posed and allowed to totally dry. Some bones may need to be glued in place.

What materials and tools will I need?
I'll bet you can guess the beginning of the answer. It depends. Mostly on the size of the animal. Something like a rabbit or chicken doesn't need too much in the way of materials and tools. It is possible to do it all with products and tools from your local small hardware store. Some wire, a drill (or dremmel), some glue, a pair of pliers. A bigger skeleton - a deer or wolf-sized animal - will need a bit more in the tools and materials department. A bigger drill, metal rods, hacksaw, vise, different sizes of wire, files, calipers, ruler, awl, caulk gun, silicone or epoxy clay, epoxy glues, hot glue, and probably some wood and wood-working tools to make a base. Some animals can be suspended in a swimming-flying-diving pose without needing a base. Some people put as much time and materials into a display stand as they do on the skeleton.

How long will it take to assemble a skeleton?
These are generally more than one weekend projects. A rabbit or chicken could possibly be done over a long weekend, but for someone who works carefully and precisely, even a rabbit might be a 30-hour assembly project. A deer or wolf-sized animal - probably 60-80 hours to assemble. A 38-foot gray whale I did took 49 days to articulate with over 800 hours of volunteers helping. Remember, we can be talking about a lot of pieces. A wolf has over 40 pieces in each foot if you count the claws and sesamoid bones. I've seen people spend a whole day just sorting out where each bone on one foot goes. Once sorted, the bones are held together with a combination of hidden metal rods, wires, and glue. The smaller the skeleton the less metal and the more glue that gets used.

What would it take to do a skeleton in a classroom?
It takes an intersection of two important ingredients. A teacher who really wants to do this and a suitable non-living animal - preferably one that is freshly dead and mature (the animal not the teacher). The animal is usually divided up into 6-12 sections, and students or teams of students each get one section from beginning to end of the project. Most classroom skeletons get cleaned, degreased and whitened. Once clean and dry, the bones offer all kinds of interesting opportunities to study anatomy, comparative anatomy, scientific illustration, even the physics and mechanics of the human body by looking how and where muscles attach (levers, fulcrums, pivits), different engineering strategies (domes and different types of joints) for making something strong and lightweight - and math! After a pose is decided upon, the groups start assembling their section of a skeleton. This takes glue, wires, metal rods, drills and drill bits, and time. It can be done in the class or as a club outside of class. A small mammal (fox-sized or smaller) can be articulated in 10-15 hours of time by an organized class. Sometimes I get called in to help. Other times teachers take this on just using the Bone Building Books. These manuals were written with teachers and students in mind, and they will take someone step by step from the cleaning process to the displaying. I've worked with classes in schools on skeleton articulations ranging from whales, to bears and moose, to seals and sea lions, to smaller animals like foxes and otters. I've done them with ages ranging from 5th and 6th graders all the way up to college classes. A universal given, when the project is done has always been a class full of very proud students who mostly want to know - when will the next skeleton project be? These projects have hooked students like no other projects they have ever encountered. Students who otherwise had very little interest in school or learning, have been known to skip lunch or come in after school to be able to keep working on these projects. Students have graduated with memories of these projects being the most favorite thing they ever did in school. With the no-child-left-behind business, it can be a hard sell for a classroom concerned solely with test scores, but the satisfaction, self-confidence and the spark for knowledge that these projects ignite, in the big picture, can be way more valuable than something that shows up on a test score.

What does it cost for materials for these projects?
Most of these projects have been fine-tuned such that they can be done with materials found even in small-town hardware stores. A small animal such as a rabbit, raccoon or chicken can be cleaned and articulated for less than $30 - if you have the tools. A medium-sized animal like a wolf or deer might take closer to $300 (with a stand) and a 30-foot whale could probably use up $3,000 worth of materials and welding.

So how does all this tie in with the Bone Building Books?

The manuals - volumes 1 through 9 - (heavily illustrated with black and white ink drawings) have step by step cleaning and assembly instructions, each according to specific groups of animals, telling you exactly how to do all the things mentioned above. (See About the Books.)The Bone Builder's Notebook (volume 10) is the companion reference book to any of the other bone-building manuals. If you work with bones or desire to work with bones, this is the answer book to questions you may have about preparing bones or skeletons for use in collections, or for display.

Please see the FAQ page for more bone building questions and answers.