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A new approach
involving CNRS scientists from various disciplines is helping to reveal
the secrets of Narbonne's retable. This altarpiece, a jewel of southern
French mediaeval Gothic art, was uncovered in the Narbonne cathedral
in 1981. Careful, sophisticated restoration work is vital to preserving
its sculpted, painted stones.
The CNRS team includes geologists from the "Hydrosciences"
laboratory (University of Montpellier 2), art historians from the
"Milieux et sociétés en France méditerranéenne:
archéologie et histoire" laboratory, and art restorers.
These experts have come together to study restoration problems, in
particular that of the presence of a hard protective layer, normally
associated with weathering, which exists beneath the painted layers
of the retable, an item which is usually indoors. Solving this problem
also contributes to understanding how to reduce the abnormal concentration
of salts in the stone which change it and can destroy the painted
layer. The team has taken a two-pronged approach to the problem: analysis
using scientific methods, and bibliographic research into methods
used by fourteenth century artisans.
The scientific analysis involved analyzing the chemical and mineralogical
make-up of the stone and paint, the pore network, and the stone-paint
contact zone using geological techniques. Preliminary results revealed
many different cases depending on the stone in question, its porosity,
and the paints used. They showed the existence of an impermeable microzone
between the paint and stone formed by the paint blocking the stone's
pores. Its connection with the abnormal concentration of salts observed
in the stone is still being studied.
These results show that the late fourteenth century sculptors and
painters who created the retable must have known enough about the
properties of their materials to work together closely when preparing
the surface of the sculpted support prior to painting.
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