The Effects of Possible Contamination on the Radiocarbon Dating of the Dead Sea Scrolls II: Empirical Methods to Remove Castor Oil and Suggestions for Redating

Abstract

ABSTRACT. While kept at the Rockefeller Museum in East Jerusalem, many Dead Sea Scroll fragments were exposed to castor oil by the original team of editors in the course of cleaning the parchments. Castor oil must be regarded as a serious contaminant in relation to radiocarbon dating. If modern castor oil is present and is not removed prior to dating, the 14 C dates will be skewed artificially towards modern values. In Rasmussen et al. (2001), it was shown that the standard AAA pretreatment procedure used in the 2 previous studies dating Dead Sea Scroll samples (Bonani et al. 1992;Jull et al. 1995) is not capable of removing castor oil from parchment samples. In the present work, we show that it is unlikely that castor oil reacts with the amino acids of the parchment proteins, a finding which leaves open the possibility of devising a cleaning method that can effectively remove castor oil. We then present 3 different pretreatment protocols designed to effectively remove castor oil from parchment samples. These involve 3 different cleaning techniques: extraction with supercritical CO 2 , ultrasound cleaning, and Soxhlet extraction-each with their own advantages and disadvantages. Our data show that the protocol involving Soxhlet extraction is the best suited for the purpose of decontaminating the Dead Sea Scrolls, and we recommend that this protocol be used in further attempts to 14 C date the Dead Sea Scrolls. If such an attempt is decided on by the proper authorities, we propose a list of Scroll texts, which we suggest be redated in order to validate the 14 C dates done earlier by Bonani et al.

Radiocarbon Dating of Historical Parchments

“…Although samples of the Dead Sea Scrolls were used by Libby to test the accuracy of 14 C dating during the initial development of the technique, and Berger et al (1972) subsequently investigated the feasibility and accuracy of the method by dating English historical legal documents, 14 C was rarely used for dating parchments until the advent of AMS dating, which required much less material than earlier conventional methods. Subsequently, 14 C dates for more of the Dead Sea Scrolls (Bonani et al 1992;Jull et al 1995;Rasmussen et al 2001Rasmussen et al , 2009, the Vinland Map (Donahue et al 2002), and several Spanish historical manuscripts (Santos et al 2010) have been published, with the dates generally being in good agreement with paleographical estimates or known ages.…”

“…carbonates formed following liming, egg, flour, and fish glue, although many of these may be of the same age as the parchment), and conservation materials applied subsequently. The effective removal of castor oil applied to the Dead Sea Scrolls prior to dating, for example, has been the subject of much discussion (Rasmussen et al 2001(Rasmussen et al , 2003(Rasmussen et al , 2009Carmi 2002).…”

“…Such lipids all have potentially different ages and it is hard to distinguish between sources, so it is advisable for pretreatment procedures to include a solvent wash to remove them. However, ultrasonication in solvents may be too harsh for more fragile samples, and simple washing or Soxhlet extractions may be more suitable (Rasmussen et al 2009).…”

So you want to do biocodicology? A field guide to the biological analysis of parchment

“…Radiocarbon dating does provide a more precise form of dating, however this comes at a cost and is also generally reported as a calibrated date range. It necessarily requires destructive sampling of at least 3-10 mg [52] which, as we have previously discussed, is not routinely accepted by most conservators and curators and can therefore only be used when the object is considered of such high importance that the potential results merits the destructive samples [53][54][55][56]. We would also advocate that any sample remaining from a radiocarbon analysis be identified as the important biobank that it is and hopefully not discarded but used for other analyses.…”

Chronologies in wood and resin: AMS 14C dating of pre-Hispanic Caribbean wood sculpture

“…Shellac is soluble in alcohol and sodium hydroxide, and so should also have been removed by the pre-treatment processes. Castor oil has been removed using a similar solvent extraction sequence involving ethanol and hexane (Rasmussen et al, 2009). The three samples treated with lanolin [5e7] were submitted to a more thorough soxhlet extraction, involving sequential 8 h washes with petroleum ether, hexane, toluene, acetone, methanol and chloroform.…”