museum natural history parisNaturally curious, you may have asked yourself how bones get from their living condition–muscle-covered, cartilage-capped, and fat-filled–to the inert, dry, aesthetically pleasing material so widely exhibited and valued. If you are not curious about how this transition takes place, you may wish to skip this post.

When a dead animal is left exposed to the elements, it takes a year or two for the soft tissues covering the bones to weather away and for micro-organisms and small insects to feast on and completely remove the fat from the bones’ interiors. (The wee beasties get in and out through the same small channels that the blood vessels used during life.) By happenstance, craftspeople may come across such naturally cleaned and dried bones on the beach, desert, or forest floor, and if so, they can immediately go to work repurposing them. During the natural transformation, however, scavenging animals may carry some or all of the bones off and destroy them.

How do scientists, museum staffs, and craftspeople hasten the transformation and ensure that the bones will still be there for their interests when the cleaning is complete? The three approaches are the same ones taken by the US Marines: land, sea, and air. For bone preparation, each course has its advantages and disadvantages. They are all accelerated if the skin, muscles, and innards are first removed, but patience will even replace this grizzly step should one desire.

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Burying the remains (deeply enough to prevent scavenging) has the advantage of being stink free. Before internment, I wrap my treasures in nylon mesh so that I can easily retrieve even the small bones in due time. This process usually takes six to twelve months. Presently I am patiently waiting on a squirrel (road kill), a moose cannon bone (hunter friend in Alaska), a chicken (Whole Foods), and a small pig (Hawaiian luau).

The same transformation from messy to beautiful is greatly accelerated by placing the remains in a bucket of water, or huge vat if you are preparing an elephant. This method is extremely offensive to the nose and so should be done far from habitation. Change the water every few weeks, ideally during a wind storm or when you have a severe cold with complete nasal congestion.

Air transformation may not be quite so stinky but still needs to be done outside and certainly not under an open window. The bones need to be wrapped in window screen or hardware cloth to prevent predation. I and others keep such weighted-down preparations on our roofs (unbeknownst to our spouses).

dermestid beetlesTo accelerate air transformation, commercial preparers and university and museum lab techs often employ dermestid beetles. These little critters love carrion and could not care less about bone, so they quickly nibble them clean, with their smallest larvae doing the inside job. Should you wish, the beetles are available for both viewing and purchase on the internet. Before considering ownership, however, understand that they need continuous feeding, so they are not practical for just a one-time harvesting of a Thanksgiving turkey skeleton, for instance.

After the transformation by whatever means is complete, a soak in hydrogen peroxide will further whiten the bones and render them lovely and ivory-like. Conversely here are two ways to absolutely ruin your hard-earned specimens. As intuitive at it might seem, do not use household bleach. It may work fine on grass stains and wine dribbles, but it permanently softens and pits the bone making it unappealing to handle and unsuitable for crafting or display. Boiling also renders them nasty, but for a different reason. It drives the marrow fat into the dense, naturally fat-free, outer portions. The fat in this new location is inaccessible to wee beasties of all sorts and leaves the bones with a permanent greasy appearance and feel.

hagfish Harvard MNH

A carefully prepared skeleton is a thing of beauty.

 

 

 

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7 thoughts on “Dry Bones: How They Got That Way

    1. Hi Suzanna,
      Who would know how fascinating bone is–unless you tell them!! Spread the word: toss your friends a bone.
      Best wishes, Roy

  1. Thanks, Roy.
    This article causes me to think in new ways about the process of natural formation of animal skeletons.
    You may have covered it in previous blogs, but what are the factors in skeletons then becoming petrified?

    Ed Patrick

    1. Hi Ed,
      Great question. Here is my non-geologist, non-technical understanding.
      Best wishes, Roy
      We say bones when we talk about Lucy or dinosaurs, but what we have are in fact stone replicas of the original bones. Fossil formation is a complex interplay of bone size and porosity along with local mineral composition and concentration, acidity, and temperature of the mud covering the skeleton. When conditions are just so, water permeating the bone leaches out a calcium hydroxyapatite molecule, which is immediately replaced with another mineral molecule that had been dissolved in the water. The bone turns to stone, one molecule at a time over tens or hundreds of thousands of years. So does the surrounding mud, but its constitution is different because it did not start out as hydroxyapatite. Then perhaps millions of years later, the sea, lake, or riverbank dries up, and if the bones weather away a little more slowly than the sedimentary rock within which they are embedded, a passing paleontologist might spot a partially exposed fossil and dig it out.

  2. Very interesting. And you are very witty as well. Personally I think burial is the best solution. Some years ago I buried a small bird my cat had killed. A year later I needed a bird skeleton to photograph for an art installation so I dug it up. It was, as you said, picked perfectly clean. Thank you. Jacki Apple

  3. Ironically I recently met an archeology professor at the local college. Last year a man was clearing some land and unearthed the skeletal remains of a Columbian mammoth. The bones were encased in plaster with the surrounding dirt. I have volunteered to help clean away the dirt. At some point we will be piecing it together although we only have about 30% of the skeleton plus tusks.

    1. That sounds exciting. In what state is this? Take lots of photos. Have fun, especially if the plaster case can be lifted onto a bench so that you can brush away with out having to lie down with your head sticking in a pit. Roy

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