The magnificent and imposing polyptych of San Michele, which arrived in the laboratory for restoration in 2004, presented complex problems of conservation. The intervention, necessary to improve the reading compromised by large deposits of dirt, altered paints and old repaints, was also very compelling considering the severe attack by the woodworms.
During the operations, an in-depth study was carried out aimed at gathering interesting technical construction information on the carpentry. Non-destructive instrumental investigations in the infrared, ultraviolet, X-ray and some stratigraphic chemical analysis on micro-samples have allowed to characterise the constitutive materials and to identify and reconstruct the pictorial tucks and the retouches made in the past in at least two different restoration interventions.
Through sketches, annotations and graphical and pad evaluations, interesting data on the executive technique of the author of this unusually rich and refined work were also recorded. The restoration work of the wooden support, in addition to the disinfection from woodworm and consolidation for imbibition of degraded wood, has also provided for the correct identification of the original parts with respect to the numerous additions and structural changes that have taken place over time, with targeted cabinet-making interventions to re-establish planeness as much as possible, reduce deformations and integrate deficiencies. The phases of fine hatching cleaning and reintegration of the pictorial gaps required outstanding skill, to combine in a satisfactory and methodologically correct way the instances of reversibility and restitution of the readability of the whole.
The impressive dimensions of the polyptych have also required the creation in the laboratory of a wooden and aluminium structural system to which the various elements were fixed, in such a way as to adequately unload the weights and allow the wood to carry out the natural expansion and shrinking movements of the fibres.
The details of the restoration operations are published in: AR Nicola, P. Traversone, C. Eulére, Il Polittico di San Michele Arcangelo restaurato, Pigna, 2006
Manual skills, technology and science in an artisan restoration workshop