Wednesday, March 24, 2010

Non-Destructive Carbon Dating

Radiocarbon dating is an inherently destructive process, because a sample of the object to be dated has to be burned, washed with acid and base, and then vaporized. Modern techniques work on very small samples, but some destruction is always involved. And, there is a problem with using very small samples. When you are working with a pinhead of material, the danger increases that what you are really measuring is not the age of the sample itself but the age of a root hair embedded in it, or even a bacterial film on the surface.

Which is why I am a little skeptical of this new technique:

Rowe's new method, called "non-destructive carbon dating," eliminates sampling, the destructive acid-base washes, and burning. In the new method, scientists place an entire artifact in a special chamber with a plasma, an electrically charged gas similar to gases used in big-screen plasma television displays. The gas slowly and gently oxidizes the surface of the object to produce carbon dioxide for C-14 analysis without damaging the surface, he said.

Rowe and his colleagues used the technique to analyze the ages of about 20 different organic substances, including wood, charcoal, leather, rabbit hair, a bone with mummified flesh attached, and a 1,350-year-old Egyptian weaving. The results match those of conventional carbon dating techniques, they say.

Of course the technique must be doing a little damage to the object -- the carbon has to come from somewhere -- but that damage could certainly be very small. What I wonder is how susceptible the process is to corruption by dirt, oil, bacteria, or anything else that happens to be on the surface of the object to be dated. We'll see, as more tests are done. If it works, it will make it much easier to date objects for which the artistic or sacred value forbids any sampling.


olga lednichenko said...

every method with have some margin or error - is that not true?

the question should be about the p-value - no?

and the R sqaured would be hard to get through

olga lednichenko
nesher, israel

John said...

With carbon dating, the question of precision is separate from the question of accuracy. Modern AMS dating sometimes gives you very precise date ranges, statistically -- like, say, 9000 BP +/- 40 -- but if you are dating the wrong thing, that might be thousands of years off. And there are weird effects, like, that dates people are getting from the burn marks pots seem in my part of the world to be a few hundred years off the dates that come from nearby hearths. My concern is that this non-destructive dating would introduce a new set of odd effects, deriving from stuff on the surface of the objects.