Why did the bioplastic hypothesis ultimately fail to convince researchers?
It seemed that bioplastic hypothesis might be an explanation for the medieval date given to the shroud by carbon dating. If you were looking for a way to dispute that carbon dating of the shroud, you had it. It didn’t play out that way.
Though it was premature of draw conclusions about the true age of the shroud you could argue. seemingly with validity, that the sheen was off the carbon dating of the shroud. Unless Gove, Garza-Valdes, Davis, et. al., were proven wrong, there was reason for reasonable doubt. Jeffery L. Sheler, writing in the July 24, 2000, issue of U.S. News & World Report, quotes Gove as saying,
There is a bioplastic coating on some threads, maybe most.” Gove goes on to say that if there is a sufficient quantity of bioplastic it “would make the fabric sample seem younger than it should be.
Garza-Valdes had said:
With a scanning electron microscope, I found the fibers were completely covered by the bioplastic coating (polyhydroxyalkanoate) and by many colonies of fungi which usually thrive on this polymer...
Many scientists found this last statement flawed because:
- There is no way to determine the definitive composition of an organic material by scanning electron microscope.
- Garza-Valdes provided photomicrograph showing a "filamentous cell" that turned out to be an ultimate cell from the flax structure.
- It is well known that such polymers (they do exist on some ancient objects) obtain their carbon material from the host (fibers in this case) and not from the atmosphere, hence they do not significantly change the C14 dating.
- The amount of material needed would need to be significant. On this point, Gove finally took exception with the bioplastic theory and agreed.
Because a bioplastic material could be easily detected, fibers from the shroud were examined at the National Science Foundation Mass Spectrometry Center of Excellence at the University of Nebraska. Pyrolysis-mass-spectrometry failed to detect any form of bioplastic polymer on fibers. Just to make sure, laser-microprobe Raman analysis at Instruments SA, Inc. in Metachin, NJ, was used to examine the fibers. This method also failed to detect any bioplastic polymer.