Recording Carbonized Papyri
The recording methods described hereafter cover most of the reasonable
ways to produce digital images from conserved papyri
scrolls. The most potential means have been studied with
more care, while the less promising methods have been discussed
The test conditions and environment were kept as constant as
testing equally comparable materials or methods. In the tests
we choosed to concentrate on the fragment no.12 and especially
to the text "Kaj allon". This example presents most of
the difficulties that cause the poor readability of
writing on carbonized papyrus.
The outcome of ordinary photography was most difficult to optimize.
Considerable amount of time was spent in trying different
illumination conditions and suitable developing procedures before
the real test photographs.
Hundreds of negatives and paper copies were made. Simultaneously,
a test set of negatives from the real Petra Scrolls was being
scanned in different commercial litographic firms, with request
to produce the best possible images.
The amount of manual work and sensitivity to faults makes
photography less appealing when comparing to modern digital
imaging techniques described next.
The direct scanning method was also somewhat difficult to test,
because a typical sample plate is larger than a typical A4- or
U.S.Letter sized flat scanner. Placed upon a scanner,
the few millimeter high edges of the scanner casing and
the glass plate cause the samples to be too high for the
scanner to focus correctly. So, the cover had to be taken
off, exposing the CCD cells to dust (that may also void
the warranty depending on the manufacturer).
Opening the cover of a scanner has to be done with special
care and in a dustless environment. The first dust
particle landing on the CCD will cause a line to appear in
all further scans, and several will render the scanner
The same illumination problems we had with photography were
also present when digitizing video signal. Fortunately,
the resulting image could be seen in real time, and so the lights
could be adjusted to optimum quite easily. The spectral
response of the frame-transfer type CCD cells of the tested
COHU 4710 video camera extends to near-infrared (950nm),
even farther than the red-extended photographic films,
so we applied the red and infrared filters to the tests.
Two different thermographic cameras were tested; the glass plate
effectively prevented the camera to detect the differences
of temperature or emissivicity in the fragments. Slight heating
to approximately 45°C with a tungsten lamp did not help.
We used Helsinki University Central Hospital's X-ray
equipment to search for differences in density.
The glass plate captured X-rays far more efficiently
than the thin, soft papyri fragments. Several variations
in power and exposure times gave, at best, flat
grey pictures without a single detail.
Back to Measurements
Back to Contents
Next: Papyri Photography
Antti Nurminen, 34044T, firstname.lastname@example.org