Shroud of Turin Image Mystery
Now that we know that the radiocarbon dating is
invalid, meaning we don't know the age of the Shroud of Turin, much of
the emphasis in shroud research has turned to trying to understand how
the images were formed.
Skeptics have long maintained several positions:
the shroud is a painting, a medieval photograph or a rubbing of a
bas-relief. More recently, it was proposed that the image was sun
bleached using a shadow mask painted on glass. None of these methods
survive scientific scrutiny.
Proponents have suggested a number of theories as
well. They include chemical processes produced by vapors emitted by a
body shortly after death such as cadaverine and putrescine, radiation
and an electrical corona discharge. A chemical reaction might be a
natural phenomenon but an explanation for radiation or any other form of
energy so far lacks a natural source explanation and seems to require a
miracle, which clearly is beyond the purview of science. So far, no
theory survives scientific scrutiny.
A Filmy Substance of Sugar
In truth,
no one knows how the image, purportedly of Jesus, was formed on
the Shroud of Turin. Scientists know that it is a caramel-like
substance, but they do not know how that substance was formed.
When the cloth of the Shroud of Turin was made,
flax fibers, about one-fifth the thickness of human hair, were hand-spun
together into linen thread. The threads were then woven into a fine
herringbone linen sheet that is about three feet wide and fourteen feet
long. These fibers, scientists now know, hold the key to how the image
was recorded on the cloth whether by a miracle, a faker of relics or an
accident of nature. It is on the surface of the fibers that the image
resides.
Scientist who examined the shroud in 1978 used to
think that some of the white fibers had oxidized and dehydrated and
turned brown. Inexplicably, they thought that this was how the image was
formed, even if they didn’t know the mechanism for this color change.
Now, scientists know that isn't the case. Instead,
a thin filmy substance that coats some of the fibers has undergone a
chemical change. It is the coating that has turned brown forming the
image. Chemists know what this filmy substance is. It is a
polysaccharide substance, a mixture of different sugars and trace
amounts of starch. And they also know what sort of chemical reaction is
needed to cause it to change color. But they still don't know how this
might have happened in a way that would form an image of a man on the
cloth.
The substance of the pictures, the starch and
saccharide mixture, is extremely thin. From microscopic observations,
chemists have estimated that it varies in thickness from about 200 to
800 nanometers. It is as thin as the wall of a soap bubble; thinner than
the invisible glare proof coating on modern eyeglasses and thinner than
most bacteria. To get an idea of how thin a few hundred nanometers is,
it helps to realize that a sheet of copier paper is about 100,000
nanometers thick.
The coating is only found on the outermost fibers
of the thread. In fact, it is only found where the fibers are close to
the surface of the shroud's cloth. In other words, the fibers inside the
thread, deep in the middle of the cloth, do not have this filmy
substance.
The coating can be removed by scraping or by
pulling it away with adhesive tape. Over the years, as the Shroud of
Turin was folded and unfolded, and spread out across rough surfaces,
microscopic bits of the filmy substance flaked away. In fact, when
scientists examined the shroud in 1978, they collected samples with
adhesive tape. Today, countless tiny bits of the coating, some including
parts of the image, are stuck to microscope slides and sampling tapes
stored in laboratories around the world.
Scientists have a pretty good idea about how the
coating got there. It wasn't brushed on or wiped on as an artist might
apply sizing to a canvas before painting. Had that been the case, the
starch and sugar mixture would have soaked at least part of the way
through the fabric. Capillary action would have pulled the mixture into
the middle of the threads. That didn’t happen. Scientists have not found
any of the polysaccharide mixture except on the surface.
It turns out that the distribution of the coating
is consistent with evaporation concentration. Interestingly, this is
consistent with the way linen was made during Jesus' era as described by
Pliny the Elder (23 to 77 AD).
If linen cloth is rinsed in a solution of water and
dissolved saccharides, and if the cloth was is then dried in the air, a
coating forms that is identical to the coating found on the Shroud of
Turin. We know that in the first century, threads on the loom were
lubricated with crude starch to make weaving easier and to prevent
fraying. The starch was then washed out of the cloth by rinsing it in
suds from the Soapwort plant. But the starch wouldn't have been washed
out completely. Trace amounts of both starch and the numerous
saccharides found in the natural soap would have remained in the wet
cloth. As the cloth dried, moisture wicked its way to the surface
carrying with it starch and saccharide molecules. The dissolved material
concentrated at the surface and remained on the fibers as the moisture
evaporated into the air.
Such a coating would have remained clear and
colorless unless it was exposed to reactive liquids or vapors such as
ammonia, or if it was heated sufficiently to caramelize it. We can
probably rule out heat because enough heat to cause the coating to turn
brown would also have caused the fibers to turn brown. That didn’t
happen. When the image is pulled away with adhesive, the remaining
fibers are completely clear. This leaves us to consider reactive vapors
or liquid. But liquid will not work; for it would have dissolved the
saccharides and carried them into the interior of the thread.
One theory is that vapors of cadaverine and
putrescine, natural vapors that emerge from a corpse, would have
produced an image. An interesting article, the
Shroud
of Caiaphas, explains this theory in greater detail. But, as the
article explains, vapors present problems, as well, because they diffuse
at various angles as they emerge from a body. It is unlikely that vapors
could produce a high resolution image.
Philip Ball, who for many years was the physical
science editor of Nature, a prestigious international weekly
journal of science, wrote a commentary in Nature’s online edition
in January of 2005. He summarized the problem well when he wrote, "[The]
shroud is a remarkable artifact, one of the few religious relics to have
a justifiably mythical status. It is simply not known how the ghostly
image of a serene, bearded man was made."
* * *
|