Diversity of the cleaning procedures including laser for the restoration of carved portals in France over the last 10 years

Abstract In France, the first laser cleaning on monuments was successfully carried out from 1993 to 1995 on the south portal of the western facade of the Amiens cathedral. Since this site, around 20 portals of famous monuments such as the Paris, Amiens, Bordeaux, Bourges, Poitiers, Chartres cathedrals, to name a few, have been restored through various methods, including laser cleaning. The cleaning procedure for the limestones on these portals has varied, in particular in the way of using laser: alone or combined with other methods like microsandblasting and poultices, preceding or following the other methods of cleaning. The procedures are described and reasons for the different practices are presented. In fact, on the site, the deontological criteria, which had assumed the initial promotion of the laser cleaning, have sometimes stepped aside in favour of the more subjective aesthetical notions linked to the presence of visible ancient treatment, patina, relics of polychromy. It is therefore possible to distinguish schematically two poles of cleaning by using laser: one consists of using laser and only laser in order to optimize the conservation of the stone and its patina whereas the other combines different techniques, including laser, in order to obtain a more satisfying result aesthetically referring more or less to how the artwork originally looked. The procedures compound also with economical preoccupations and integrate laser with other methods to reduce its use in composite cleanings or for finishing.