Ah, but with the AMS technique, they can bombard the sample with an electron beam to do a depth profile, sputtering off successive layers. They can then compensate for exactly that problem.
(Post 3:00 AM posting time noted...)
Geez, up late last night, Wonder? Or time-zone differences?
My apologies. I *assumed* that samples FOR THE PREVIOUS TESTS had been extracted from the Shroud, then dissolved, shredded, bent, folded, stapled and mutilated to prepare for testing, then tested.
If there are tests which can be performed in situ as it were, and which do not require mechanical sampling / mixing of the sample, I'm all for it in principle--if they are nondestructive.
Other disclaimers are possible, including the possibility that portions of the cloth were re-weaves or of different ages for whatever reason. The cloth, whatever its origin, has had quite some history. Disregarding the possible effects of its travails through time on the experiment would not be sound science. And if the effects of fire, travel, water damage, whatever, cannot yet be quantified, it would be more honest on the part of all parties to affix a big "We're just not frigging sure" to all pronouncements.
Cheers!