Why and When to use Radiocarbon Dating

Radiocarbon dating is an excellent tool in the study of organic materials. It can provide hard scientific evidence of age, and is immensely useful in the detection of forgeries, and the authentication of artifacts.

- Radiocarbon dating may be used after an object has been examined to determine that the sampled
area is representative of the whole object. These additional types of examinations will vary according to the media and the type of artifact to be sampled.

Radiocarbon dating, also known as “C-14 dating”, can be used to determine the approximate age of many organic materials. It can be used for objects ranging in age from a few years, up to roughly 50,000 years, in age. Radiocarbon dating has been around for a considerable time, and much is known about the benefits and limitations of the test.

Advantages

1) Using Accelerator Mass Spectrometry radiocarbon as compared to “conventional” testing, the sample size is very small.
2) It can be performed on a broad range of organic materials.
3) The margin of error is relatively small.
4) There is a large database for comparison.
5) It is available from a large number of facilities.
6) It can be used to date certain types of iron objects.

Disadvantages

1) Even with prepaid expedited service, the test requires at least four weeks to obtain results, generally longer.
2) It is moderately expensive, up to $1000 including shipping and sampling.
3) The sample is destroyed, so no further tests can be performed on it.
4.) Certain contaminates can cause a wider margin of error or even a complete misread, even though all reliable facilities do various decontamination procedures prior to testing.

Paper is a material which is well suited to radiocarbon dating, if a sufficiently large sample can be obtained. This is one of six(6)
Western Tibetan manuscript pages, with writing on both sides, and finely painted illuminations. One page was chosen for testing. Since the artifacts were in very good condition, it was decided that it would be unacceptable to remove a single large sample. Instead, small bundles of fibers were removed from around the top and side edges. The sample was removed by an independent contractor, and sent to Beta Analytic for AMS radiocarbon analysis. The results dated the paper from 980 – 1160 CE, at a 95% probability. This overlapped the early end of the proposed 11th -15th century CE age range for the manuscript. It should be noted that, as with wood, the test indicates the age of the paper fibers. Depending on the type of material used to make the paper, there may be a difference in the age of the paper and the artifact as a whole. In such cases, C-14 data is combined with art history research, and ink and pigment inspection.

Wood is well suited to radiocarbon analysis, and this painted panel was a good candidate, as there was no evidence of contamination of the wood by any oily substances which might be difficult to remove prior to testing. A sample of this rare Sassanian/Sogdian style wooden, painted architectural fragment, found in China, was removed and sent to Rafter Radiocarbon Laboratory, in New Zealand, for testing. The results dated the wood to 348 – 533 CE, at a probability of 95%. This example was originally attributed to the Tang Dynasty but a Six Dynasties (220-581 CE ) attribution was also considered to be reasonable. It is, of course, possible that the wood dates earlier than the painting. However, a separate examination was also conducted to insure that the pigment was original to the period. After the sampling, conservation procedures were initiated to properly preserve the wood and pigment.

These exceptional hand woven pants are made from a combination of thread types. The vast majority of the pants were made from thread dyed red, yellow or blue/green, thus it was this material which was sampled for radiocarbon analysis. A small sample, roughly 1.3 cm square, was removed and sent to the NSF AMS Radiocarbon Laboratory at the University of Arizona for testing. The results indicated that the textile dated from 800 – 510 BCE, at a probability of 95.4%. This is representative of the Spring & Autumn Period (770-481 BCE), of the Eastern Zhou Dynasty (770-256 BCE) making this artifact among the earliest known extant examples.

Among ancient Chinese metal antiquities, iron objects are relatively rare, due to the high corrodibility of the metal. This metal is of great interest, as the Chinese were making cast iron well in advance of other civilizations. If smelted with charcoal, instead of coal, the metal has the potential to be carbon dated. A metallographic and metallurgical examination of this Tang Dynasty horse statue found it to be made from mottled cast iron, and in very good condition and of great age. A C-14 analysis then determined the carbon content of the metal. (If charcoal was used to smelt the iron, impregnated traces of carbon derived from the charcoal vapor can be measured). A sample was sent to the NSF AMS Radiocarbon Laboratory at the University of Arizona for testing. The results of the analysis dated the charcoal to 660 – 780 CE, consistent with the Tang Dynasty. Combined with the metallographic and metallurgical data, this result is considered representative of the statue as a whole.