BIOCORROSION AND BIODETERIORATION OF ANTIQUE AND MEDIEVAL GLASS

Over the past few years we have examined various antique and medieval glasses with regard to general biogenic damage, biopitting (crater erosion), biocrusts, and opalescent and white biogenic films. Experiments were carried out on pieces from Roman glass bottles excavated near Abu Tor, Sinai, some pieces of green and blue glass from Cologne Cathedral, some pieces from a little church in Evreux, glass samples from the fortress of the former Dukedom of Delmenhorst near Oldenburg, and some neolithic flint tools from the Negev Desert, Israel. Modem glass from a pigsty (19th century) additionally has been used for laboratory experiments on the attack of glass surfaces by fungi and bacteria. Some of the bacteria used in these experiments were isolated from the ancient pieces of glass. Biopitting with structures very similar to the biopitting of marble and limestone was found on almost all specimens. Lichens were not identified directly, but fungi and algae were observed in the pits as well as under the thin layers exfoliating from the Roman glass bottles. Initial steps of colonization and the potential for heavy-metal accumulation by the isolated bacteria have been shown in laboratory experiments. A fractal dimension of diffusion-limited disaggregation (DLD) is suggested as one possible explanation for the characteristic form and structure of the microbially induced and shaped biopitting patterns. A biopitting classification is suggested.