To confirm the feasibility of dating the shroud by these methods an intercomparison, involving four AMS and two small gas-counter radiocarbon laboratories and the dating of three known-age textile samples, was coordinated by the British Museum in 1983. The strip came from a single site on the main body of the shroud away from any patches or charred areas.
The results of this intercomparison are reported and discussed by Burleigh . Three samples, each ~50 mg in weight, were prepared from this strip.
Photography of the shroud by Secondo Pia in 1898 indicated that the image resembled a photographic 'negative' and represents the first modern study.
Subsequently the shroud was made available for scientific examination, first in 19 by a committee appointed by Cardinal Michele Pellegrino .
As Controls, three samples whose ages had been determined independently were also dated.
All laboratories examined the textile samples microscopically to identify and remove any foreign material.
The Oxford group cleaned the samples using a vacuum pipette, followed by cleaning in petroleum ether (40° C for 1 h) to remove lipids and candlewax, for example.
At the same time, the British Museum was invited to help in the certification of the samples provided and in the statistical analysis of the results. The age of the shroud is obtained as AD 1260-1390, with at least 95% confidence. The three containers containing the shroud (to be referred to as sample 1) and two control samples (samples 2 and 3) were then handed to representatives of each of the three laboratories together with a sample of the third control (sample 4), which was in the form of threads.
The procedures for taking the samples and treating the results were discussed by representatives of the three chosen laboratories at a meeting at the British Museum in January 1988 and their recommendations = standard deviation) errors, of the Shroud of Turin and control samples, as supplied by the three laboratories (A, Arizona; O, Oxford; Z, Zurich) (See also Table 2.) The shroud is sample 1, and the three controls are samples 2-4. The sampling of the shroud took place in the Sacristy at Turin Cathedral on the morning of 21 April 1988. All these operations, except for the wrapping of the samples in foil and their placing in containers, were fully documented by video film and photography.
Even for the first investigation, there was a possibility of using radiocarbon dating to determine the age of the linen from which the shroud was woven.