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James Enterline wrote:
At 04:00 PM 12/10/2009, David Bradbury wrote:
James Enterline wrote:
At 04:50 PM 12/9/2009, David Bradbury wrote [on detection of tannic
acid in the Vinland Map ink):
Both FTIR and Raman spectroscopy, which have been used on the Vinland
Map ink, are theoretically able to do the job, but neither of the
analysts responsible reported relevant peaks.
This may be simply because neither were looking for such peaks. This
is the whole reason I keep saying that someone should do my experiment
with a more open mind. Farther on this right below.
It seems clear from the way he abandoned the "alkyd resin" theory that
McCrone at least did approach his FTIR analysis with an open mind; why
do you assume he would not have reported tannic acid if he had found it
in significant quantities?
(rhetorical question!)
it was not until Walter McCrone applied FTIR in the 1990s that he was
able to make a fairly confident statement, namely that the binder
appeared to be based on gelatin made from skin.
Indeed, McCrone's confidence in that statement seems more justified by
spectroscopy than some other grandstanding of his. However, his
allusion to it as "the binder" is an assumption for which Olin
provides an alternative, that it results from hydrolysis of the
parchment collagen in situ.
By "the acid present due to the deterioration of an iron gallotannate
ink" But the iron is absent, and as far as we know, the gallotannate is
absent too. Also, I've seen a very large number of medieval documents
written with iron gall ink, and I don't recall a single one in which the
yellow stain of deteriorated ink appears to be sitting on top of the
parchment. In short, some fairly extraordinary chemistry is required to
create the conditions on the Vinland Map from a starting point of an
iron-gall ink, and despite over 30 years of trying, Mrs Olin doesn't
seem very close to reproducing that chemistry.
Furthermore it is still not determinative between tannin and gelatin
for the following reason: His published spectrum (Fig. 3 in his 1999
paper) is cut off at the left just before one would expect the peaks
(dips) for tannin at 0.254 and 0.280 microns. It would be interesting
to know if his unpublished raw data includes any points in that
neighboring region. The Brown & Clark graph has a corresponding
vacuum at its right edge where tannin might appear.
...
I'll let you know if I learn anything helpful.
There's too much titanium underneath the surviving parts of the black
layer of the ink.
Who's to say how much is too much?
In general (though with massive variations due to the crude mixing of
the ink) there is a positive correlation between the amount of black
crust and the amount of titanium in the ink, but the Raman analysis
shows that the black carbon crust is definitely on top of the anatase.
There are simple explanations for this (the anatase is in a layer that
was applied to the paper before, or at least with, the carbon) and there
are one-in-a-million fluke explanations, such as:
The bleaching / transfer I suggested would leave the temporarily
re-fluidized ink vulnerable to lateral transfer of anatase under any
black film from mechanical action of the applying brush (as well as
diffusion).
Through the thickness of the tissue?
Furthermore, this episode could introduce a new plausibility for
Olin's and Cahill's ink-separation hypothesis. Carbon in the
original ink, now fluidized in an alkaline environment, might ball up
toward the center of the line.
So the ink fluidized enough for carbon to rise to the surface, and
anatase from the bleacher's tissue to sink into it, but not enough to
blur or feather. Neat.
The rare examples of mis-registration of the black layer could have
been caused by shear forces when the bleach brush swept a bubble aside.
Except that the one glaring example of mis-registration (the British
west coast) shows a clear structure, as if applied with a nibbed pen.
When everything dries out, any anatase deposited on the plain
parchment could fall off and the carbon could begin flaking away.
The evidence shows one or two factors (to be explained in a future
paper, or at the hypothetical conference) which tend to make that
scenario unlikely.
In any case, McCrone's tale of a forger sitting down and painfully
retracing, almost perfectly, a map he had just painfully fabricated is
too much to swallow.
It is until you consider the actual state of the map. If the British
Museum investigators were right in observing that the finest writing
tended to lack the black crust, and McCrone was right about most of the
black crust from the main lines being removed deliberately, then the
"painful" retracing could be a much more casual process, applying the
carbon fairly rapidly to the major lines and to random points in the
fine writing, then scraping most of it away, particularly where it was
badly matched with the underlying yellow.
It is too circular in motivation. The conclusion of forgery surely
came before the hypothesis of retracing.
Not really. The British Museum team were the first to hypothesise
retracing- but, inhibited by Yale from using high-powered microscopes
with bright light, they guessed that the carbon-like black traces were
underneath the yellow, not on top, which would mean they were the
remains of a mostly-erased preliminary graphite pencil line, about a
century before graphite pencils were invented. That was just one of a
number of factors (including the mismatch between the ink's
iron-gall-like appearance under visible light and its very
non-iron-gall-like appearance under UV and IR light; plus the strange
appearance of the parchment itself under UV) which led them to declare
the Map suspect.
And even before he could have lifted a pen, the forger had to sit down
and dope out the Latin cryptograms he was going to incorporate into
the inscriptions, an art not practiced since the middle ages. And to
what end nowadays?
Multiple cryptograms using multiple cryptographic systems. To what end
in the Middle Ages? Are they real, or figments of overactive
cryptanalytical imagination?
David Bradbury
Whitehaven, England
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