Following this intercomparison, a meeting was held in Turin in September-October 1986 at which seven radiocarbon laboratories (five AMS and two small gas-counter) recommended a protocol for dating the shroud. The samples were then taken to the adjacent Sala Capitolare where they were wrapped in aluminium foil and subsequently sealed inside numbered stainless-steel containers by the Archbishop of Turin and Dr Tite.
In October 1987, the offers from three AMS laboratories (Arizona, Oxford and Zurich) were selected by the Archbishop of Turin, Pontifical Custodian of the shroud, acting on instructions from the Holy See, owner of the shroud. Samples weighing 50 mg from two of the three controls were similarly packaged.
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.
Zurich precleaned the sample in an ultrasonic bath.