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 very shortly.

Experimental Setup

The test conditions and environment were kept as constant as possible while 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 practically useless.

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,