By Dr. Elisabetta Boaretto
Department of Environmental Science
& Energy Research (ESER)
Radiocarbon Dating Laboratory
Radiocarbon dating determines the concentration of 14C relative to 12C in the material analyzed, and from this result the 14C age in year BP (Before Present) is calculated and calibrated to historical years.
Of the two items here considered, Jehoash tablet and James Ossuary, only the Jehoash tablet was analyzed for 14C by the Beta Analytic Laboratory (USA).
1. Sample collection
The tablet of Jehoash was brought to the Israel Museum for identification and to recover material that could be submitted for radiocarbon dating.
The Director of the Israel Museum Chemistry Laboratory for Restoration (SIMIA), Dr. David Bigelajzen, scraped from the letters part of the patina. He found that this patina was very soft and easy to remove. The amount recovered from the letters was considered too small for the radiocarbon determination and more patina was scraped from the side and from the back of the tablet. No attempt was made to keep separated the two different patinas.
All the material was sent to Beta Analytic Laboratory (Florida, USA). The date obtained was 2250'40 year BP which calibrated ('2σ, 95% probability) corresponds to the interval 390-200 BC.
2. Dating material from the tablet
The best available material for dating, represented by the patina inside the letters, is a mixture of pure clay mixed with chalk and some carbonized material (see Prof. Yuval Goren's report).
These three types of material could have been separated chemically, mechanically and/or by heavy liquids and measured for the radiocarbon content. The three dates would have been the radiocarbon ages of the material, but the relation to the time the inscription would need some interpretation.
a. Chalk comes from a geological formation and therefore is beyond the range of 14C (50,000 year BP). This material is therefore not related to the inscription.
b. Clay particles may contain organic matter, whose formation and inclusion in the clay are unrelated to the time of the inscription. Therefore this organic matter can be either older or younger than the inscription and therefore its age is not significant for the tablet. In this case knowing the context and the sediments where the tablet was found would have been helpful for the control.
c. Carbonized particles: these were probably the final material dated by Beta Analytic. Their report mentions that the material (patina) provided enough carbon for a good dating. No more details are given. The conventional radiocarbon age was 2250'40 year BP which calibrated (2σ, 95% probability) 390-200 BC. This result post-dates the assumed time the inscription was made (9th century BC). This might be regarded as support for the authenticity of the tablet, as the tablet should have been written before. But as the archaeological context is not known, the possibility that the charcoal is a recent addition (on purpose) cannot be excluded. This last hypothesis is supported by the characterization and composition of the patina provided by Prof. Yuval Goren.
A general conclusion is that radiocarbon dating of the patina on the Jeohash tablet does not give a conclusive proof to the authenticity of the inscription.
In the case of the James Ossuary the task for radiocarbon would be to try to date the varnish or the patina on the Ossuary and inside the letters.
With the evidence that the inscription cut through the natural patina and varnish present around the ossuary, and with the type of 'patina' identified by Prof. Goren inside the letters, the dating would not be significant for the authenticity. The chalk seen inside most of the letters is not an ideal material for dating and for answering this type of question.
I would therefore consider it very difficult to have any definitive proof of the authenticity of the inscription on the ossuary based on the radiocarbon dating of this type of material.
The radiocarbon dating provided the age of the material analyzed. Based on the characterization of the material examined in Jehoash Tablet and James Ossuary, the 14C content would not have supplied a proof of authenticity.
For both items it should be also considered that the exposure of the items to the atmosphere, in different environments would increase the risk of contamination with modern 14C and consequently add more uncertainty to the interpretation of the results. This should be kept in mind in the future, when considering how to treat and preserve items like these.