Dear Zooarchaeologists,

I have been preparing animal skeletons for many years, ammonia and caustic soda are not really to be recommended – they can smell and they may damage the bone. Ammonia which I have tried, also works very slowly. There are mixtures of organic solvents that will degrease quickly but these are often toxic/carcinogenic and should not be used. However there are commercially available degreasing machines that are sealed and use such mixtures but are very expensive. They are used for degreasing car motor parts for example.

The best way, and the method I use, is to soak for a few weeks in acetone. Acetone is somewhat toxic and is also inflammable, so should be done away from living areas. I use a gradient of jars or tubs of acetone from greasy (i.e., much used) to cleaner.

For full details see:

Davis, SJM and Payne, S. 1992 101 ways to deal with a dead hedgehog: notes on the preparation of disarticulated skeletons for zoo‑archaeological use. Circaea 8, 95‑104

http://www.envarch.net/publications/circaea/8.2/8-2-whole.pdf#page=37(Spanish translation by M. Mondini, 2003. 101 modos de tratar un erizo muerto: notas sobre la preparación de esqueletos desarticulados para uso zooarqueológico (traduccion de M. Mondini). Archaeofauna 12,203-211)

Davis, SJM. 2001 Blood, bones and ladies' tights, or the things we do in our laboratory. New York, Rubber Band Society Gazette 1 (1), 1 & 6

Davis, SJM; Baker, P.; Payne, S. and Revill, M. 2003 (On preparing animal skeletons: a simple and effective method. International Council for Archaeozoology Newsletter 4 (1) 4 and 15

Here is what we wrote in the ICAZ Newsletter on degreasing:

Bones generally contain a lot of grease.  This means that (unless the unfortunate animal died of starvation) it will be necessary to degrease. If this is not done, the bones can become unpleasant and smelly.  Over the years, grease breaks down as a result of bacterial decay and the resulting acids attack the bones. Degreasing is therefore very important and is done by leaving the bones (small specimens are better left in their tights) in acetone for several weeks.  (Chlorinated degreasing solvents are best avoided, as they are mostly toxic and/or flammable and/or carcinogenic.)  Move specimens through a "sequence" of jars containing increasingly clean acetone.  The greasiest specimens go into Jar 1. Specimens are then moved to Jar 2, which contains cleaner acetone and thence on to Jar 3, which contains the least greasy acetone.  Fish grease being rather light, tends to dissolve out quickly, so fish skeletons de-grease rapidly.  Degreasing old museum specimens may take several months, as old grease seems to be harder to dissolve.

The degreased specimen is then dried. Some zoo-archaeologists like clean white specimens and bleach them.  But chemical bleaches can damage bone and the dazzling white may obscure surface modelling and small surface details.  This can be a particular problem with small bones when viewed under the microscope.  One easy remedy is to stain with tea - black Indian or Ceylon tea being best. Pour hot strong tea over the bones; leave them a few minutes, and then wash and dry.  Staining may also be useful to distinguish certain parts of the skeleton, say left side from right.

Degreasing by the way does not turn bone white. I would also recommend removing all grease where possible. The long-term presence of grease will cause smells and the breakdown products may be acidic and therefore damage the bone.

I hope this helps. If anyone needs advice etc, do not hesitate to contact me!

Simon Davis

De: Analysis of animal remains from archaeological sites [mailto:[log in to unmask]] Em nome de [log in to unmask]
Enviada: quarta-feira, 18 de Julho de 2012 15:45
Para: [log in to unmask]
Assunto: [ZOOARCH] Bone degreasing problems

Degreasing can be tricky.  The absolute best way is with a commercial degreaser, or other solvent.  Automobile lacquer thinner works better than anything else I've ever used.  But of course there are issues with health effects of sovlents and the need for adequate ventilation that have to be addressed.

Other than that, water maceration aided by ammonia seems to work the best.  Here also there are drawbacks - you have to get all the ammonia out of the bones before they dry, so repeated soakings and changes with fresh water are needed, which can be a bit wasteful of water.

It is important, in my view, to avoid getting all the grease out of the bone.  A small amount of grease keeps the bone from becoming overly brittle and cracking.  It also makes photographing the bones much easier. Pure white bones, particularly if you commit the sin of bleaching them (even with H2O3) are so brilliantly white that surface features become hard to even see, let alone photograph, and you end up having to soak the bones in tea to get good pictures.

I've never found the drilling technique very helpful, but some of the old time preparators always used it, especially for large mammals.  Helmet Fuchs at the AMNH always drilled the long bones.  H. Chubb never did, other than for mounting purposes.

Rich

Richard S. White

International Wildlife Museum

Tucson, AZ 85745

In a message dated 7/18/2012 7:16:37 A.M. US Mountain Standard Time, [log in to unmask] writes:

Pam, yes, I've seen the drilling technique used by Angelos used
successfully. Sometimes the holes are placed vertically, by drilling
straight into the ends of the bone parallel to the shaft. This is
generally done because the skeleton is intended for mounting and this
hides the blemish. But Angelos is right that it would be better to avoid
the trabecular and/or spongy bone that lies at the ends.

One does note that when a long bone such as a tibia seems hard to
de-grease, the greasy areas tend to not be toward the center of the
shafts, but rather at the ends of the bone, as if the fatty marrow had
indeed been mobilized by the usual simmering in water, and had flowed out
toward the ends of the bone, but then had been unable to find an efficient
way out.

I am afraid that the only technique I've ever used to mobilize the grease
is to simmer the bones in water. I do try to avoid outright rolling boil,
as especially with the smaller elements or with flat elements can produce
warping or even decalcification. I don't think that drying the bone, i.e.
placing it in front of a heater or out in the California sunshine would do
much, at least not in any reasonable amount of time. When we pick up bones
lying out on top of a field someplace which Mother Nature has been working
on, almost always they have been lying out in sunshine and rain for at
least a year if not more. -- Deb Bennett

>