Augmented carbon 14 dating dedicated to Tribal Art

The CIRAM laboratories, specialists in carbon 14 dating since 2005, date your wooden, ivory, textile art objects. Thanks to advanced technologies and our teams of researchers, we date and analyze your ceramic, bronze, ivory, glass, but also wood objects.

For Tribal Art, our scientists are exposed to a problem: C14 dating is reliable for all periods, but it is not accurate for the last 300 years. Thanks to multiple sampling and a multidisciplinary approach, CIRAM scientists are able to circumvent this problem to deliver precise dating to within a few decades.

Precise dating of Tribal Art using the C14 isotope

Developed in the 1950s by Nobel Prize-winning chemist W.F Libby, radiocarbon dating is an effective method for dating organic materials such as wood, ivory, teeth, bones or even leather.

Used in the art world, but also in archaeology, it allows the analysis of artifacts up to 60,000 years old. But carbon-14 dating was a restrictive analysis until the 1980s, since it required a large sample (one gram of pure carbon). The development of particle gas pedals and mass spectrometry, AMS, has made it possible to divide the amount of material required by a factor of 1,000, and thus to preserve ancient remains as well as possible.

It is thanks to this revolution in the world of dating that it is now possible to use it on art objects, without altering the work.

Beware, it is possible to date the felling of a tree or the death of an elephant, but it is impossible to define the date of shaping the object (the sculpture for example).

Dating method thanks to carbon 14

Carbon 14 (also called radiocarbon or 14C) is a radioactive isotope of carbon whose half-life is equal to 5730 years. Its concentration will be divided by two every 5730 years. During its existence, a living organism assimilates carbon without isotopic distinction, because the proportion of 14C in relation to total carbon (12C,13C,14C) is the same as that existing in the atmosphere. Radiocarbon dating is therefore based on the presence of carbon in each living organism (of the order of 10-12 for the ratio 14C/C total). When the organism dies, exchanges with the atmosphere cease and the amount of carbon 14 decreases according to a known exponential law.

The difference between gross ages and calibrated dates

C14 dating is expressed in gross age called "Before Present". This age is based on the assumption that the 14C concentration has been constant in space and time. However, this assumption is false since we now know that C14 varies according to several factors such as temperature variations or geographical position (between the northern and southern hemispheres). To correct these fluctuations, the scientific community has established a calibration curve. It is for this reason that our scientists calibrate the raw C14 ages in order to obtain calibrated dates.

There is an important difference between raw and calibrated ages. The uncertainty on the raw age is more or less 20-25 years while it can extend over several hundred years with calibrated dates.

While several hundred years of difference is not problematic for archaeology where we cover distant and often extensive dates, it becomes problematic for artworks dating from the 18th, 19th or 20th because it becomes impossible to differentiate between periods.

A specific method for dating tribal art

As explained above, the uncertainty of the calibrated age is problematic for objects dating to the 18th, 19th, or 20th century: this is called the Suess effect. This is the case for tribal art where the vast majority of works were made with wood cut 200 or 250 years ago. The C14 does not allow to differentiate a work made less than 250 years ago.

To overcome this problem, CIRAM laboratories have been developing for several years a new method to reduce this interval.

Our scientists are based on taking multiple samples from the center of the wood to the outside. Each sample therefore allows us to trace the history of the tree. We combine carbon dating and xylological study of the wood (scientific study of the wood) in order to fully understand the physico-chemical characteristics and species of the wood used.

Thanks to this multidisciplinary approach, our scientists combine:

• Physical chemistry (with carbon-14 dating);
• Agronomy (xylology);
• Applied mathematics (statistical processing);
• Archaeology;
• Art history.

This global method drastically reduces measurement uncertainties for carbon-14 dating of modern artworks.

The CIRAM laboratories, a specialist in carbon-14 dating, therefore provide accurate dating to within a few decades.