Dear Greg,
I agree improved methods are always desirable. However, you should caution
the reader as follows:
1. You set up a straw man that castor oil is a problem, perhaps it is.
2. the tests done in Copenhagen were done on medieval parchments and not
any DSS samples, and
3. the castor-oil effect was studied for the maximum contamination (perhaps
excessively...?) - a small amount used in the '50s might have little
effect.
4. the conclusion that the pretreatment "could not have removed all of the
oil" first of all assumes that the samples were all treated with castor
oil, and that this treatment affected the age. There is no proof this is
the case, although I agree one cannot exclude it completely.
5. the fact that most of the samples gave the expected age tends to argue
against the entire argument - do you propose all of the samples are 300 yr
too young and the oldest DSS are really 400-450 BC?
I would also note that the paper of Jull et al discusses treatments with
acetone. One could easily do addition studies with more complex solvent
extractions (as I believe Rasmussen et al recommend).
Tim Jull
University of Arizona
Greg Doudna wrote:
>
> Conclusion:
> 'Our experiments demonstrate that the AAA-treatment used in
> the Zurich and Arizona 14C series could not have removed all
> oil, whether fossil or modern, possibly introduced into the
> DSS fragments.
> 'Lest the implications for Scroll studies be overlooked, this
> conclusion implies that the two series of 14C datings of the DSS
> that have been conducted up to the present (Bonani et al. 1992
> and Jull et al. 1995) cannot be guaranteed to have removed all
> of the modern carbon present in any samples if they had been
> contaminated with castor oil and hence could have produced
> some 14C dates that were younger than the texts' true ages.
> 'It is therefore necessary to devise a revised procedure capable
> of removing all castor oil in order to enable individual Qumran
> text 14C datings to be relied upon with confidence. It remains
> to be seen whether a similar conclusion applies to DSS samples
> that have been treated with British Museum Leather Dressing.'
> <end conclusion>
>
> (Comment [not in the published article]: In the body of the
> article, the data based on testing of medieval parchment samples
> intentionally contaminated
> and then cleaned and dated, compared to identical control
> samples uncontaminated and dated, show the maximum possible
> effect of castor oil contamination on a Qumran fragment--if totally
> saturated--would be c. 300 years erroneously young. The actual
> extent of contamination--in cases where this was a factor--much
> more likely be only a fraction of total saturation, and after the AAA
> cleaning done by Zurich and Tucson, would give dates erroneously
> offset toward modern by much less than 300 years. Since the
> extent of castor oil contamination in any given case cannot be
> known, there is no means to calculate a specific offset, apart from the
> calculated upper limit that will not exceed 300 years error. It
> must be emphasized that there is at present neither evidence that
> castor oil was present on any of the Qumran text samples that
> were dated, nor evidence that castor oil was not present on any
> of the Qumran text samples that were dated. All we know is that
> there was use of castor oil on fragments in the Rockefeller
> Museum in the early days and, in light of the data reported here,
> we have a problem that needs solving.--GD)
>
> Greg Doudna
>
For private reply, e-mail to "A. J. T. Jull" <[EMAIL PROTECTED]>
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