CNR ExploRA

Contributo in atti di convegno, 2019, ITA

PATINATURE ARTIFICIALI SU MODELLI DI GESSO, INDIVIDUAZIONE DELLE SOGLIE DI DANNEGGIAMENTO IN SEGUITO A PULITURA LASER

Veronica Ruppen, Silvia Cerea, Elisa Isella, Francesca Mancini, Donatella Bonelli, Antonio Sansonetti

Accademia di Belle arti di Brera; ICVBC CNR

The cleaning of plasterworks could be often complicated by the presence of surface materials, originating from molding and patinas. Lasers allow dry cleaning with high selectivity, but guidelines for the cleaning of plasterworks finished with intentional patinations are unavailable. A set of tests was conducted to identify the range to perform a correct laser cleaning on plaster model samples patinated with beeswax, de-waxed shellac, Arabic gum and boiled linseed oil, using three laser systems: Nd: YAG devices at 1064 nm and 532 nm, both in Q-Switch, and a Er: YAG at 2940 nm, starting with the smallest values of fluence and repetition rate. The effects of laser cleaning on model samples were evaluated with colorimetric, gloss, contact angle measures and stereo-microscopic observations; considering the results obtained, damage was identified on the patina and/or on the plaster substrate with the Er: YAG system, starting at a minimum of 0.50 J/cm2 and a repetition rate of 1 Hz, with the exception of the shellac treatment, which showed neither morphological or optical variations, up to the fluence of 1.25 J/cm2 with repetition rate to 5 Hz. The shellac had variations in color with the Nd: YAG at 1064 nm @ 0.79 J/cm2 and a 2 Hz; no chromatic variations resulted for the remaining three patinas in the range of fluences tested, with values between 0.31 J/cm2 and 1.1 J/cm2, with repetition rate up to 3 Hz. No effects were detected when cleaning with the Nd: YAG at 532 nm, which was effective to 2.4 J/cm2 with increasing repetition rate, up to a maximum of 2 Hz.

Aplar Applicazioni Laser nel restauro, Firenze, 14-16 settembre 2017