La conservazione degli apparati decorativi del pronao della BASILICA DI Sant’Andrea a mantova

Andrea Alberti1, Elvira Boglione2, Anna Brunetto3, Danilo Biondelli4, Daniela Lattanzi5, Paolo Pagnin2, Elena Romoli5, Laura Sala1, Antonio Sansonetti4

1 Soprintendenza per i Beni Architettonici e Paesaggistici di Brescia, Cremona e Mantova, andrea.alberti@beniculturali.it; laura.sala@beniculturali.it

2 Lithos S.n.c., Venezia, lithos.ve@libero.it

3 Restauri Brunetto di Brunetto Anna, Vicenza, annalaser@alice.it

4 Istituto per la Conservazione e la Valorizzazione dei Beni Culturali, ICVBC-CNR, Milano, sansonetti@icvbc.cnr.it

5 Direzione Regionale per i Beni Culturali e Paesaggisti della Lombardia, Milano, daniela.lattanzi@beniculturali.it, elena.romoli@beniculturali.it

ABSTRACT

The complex conservation work regarding the pronaos surfaces of the Basilica of Sant'Andrea in Mantua has recently been completed. The coffered vaults exhibit stucco decorations composed of a white plaster body or of a pinkish one and coated with either a white (on the relief) or a greyish finish (in the backgrounds). This finish is mainly composed by a gypsum layer with an extensive presence of calcium oxalates, even if in some samples a lime ground has been detected. Restoration works executed in the 1830s by Paolo Pianzola, radically modified the 15th century facade and pronaos, reconstructing the painted decorations with new materials, as they were deemed too deteriorated to be preserved. Then the painted decorations and the rosettes, made of gilt wood, were replaced with relief made of a material called by Pianzola stucco-forte; hence the current result, is a neoclassical reading of the Alberti facade.

Preliminary tests for cleaning the surfaces, which were covered by overpainting, soiling, and soluble salts, was carried out with Nd:YAG lasers in QS, LQS, SFR regimes, with the best effectiveness being obtained by laser QS with λ 532 nm. The tests conducted were useful in choosing the cleaning methods in order to obtain the desired results without any discoloration to the chiaroscuro finish and avoiding any damage to the stucco surface.

Key-words: Mantova, Sant'Andrea, Alberti, pronao, stucco, laser cleaning, Nd:YAG.