What did the Thermochimica Acta article say?
A significant paper was published in international, peer-reviewed scientific journal Thermochimica Acta on January 20, 2005 (Vol. 425, pages 189-194). It was written by Raymond N. Rogers, a chemist from the Los Alamos National Laboratory, University of California. Rogers had previously accepted the 1988 carbon dating but had revised his views. He concluded that the Shroud is significantly older than the carbon 14 tests had suggested. The abstract of the paper reads:
Preliminary estimates of the kinetics constants for the loss of vanillin from lignin indicate a much older age for the cloth than the radiocarbon analyses. The radiocarbon sampling area is uniquely coated with a yellow–brown plant gum containing dye lakes. Pyrolysis-mass-spectrometry results from the sample area coupled with microscopic and microchemical observations prove that the radiocarbon sample was not part of the original cloth of the Shroud of Turin. The radiocarbon date was thus not valid for determining the true age of the shroud.
What Rogers had found was clear evidence of mending. He found madder root dye, an organic gum and aluminum presumably as the dying mordant alum. He found splices dyed so that newer thread appeared as yellowed by age as older thread. And he found unexpected high levels of vanillin in the sample, given that the rest of the cloth did not have any remaining vanillin.
The problem in carbon dating is sometimes referred to as material intrusion: new material intruding on old material. The mixture results in an erroneous date, something of an average of the two. Estimates by textile experts suggest that as much as 60 percent of the carbon dating sample was new thread. This seems to be the result of mending in the 16th century. The amount is sufficient to change the date of a first century shroud to the medieval dates arrived at by the carbon 14 dating.