The Pettenkofer Method in Italy (1865–1892): Causes and Effects of Regeneration of Varnishes
Thanks to an unpublished documentation from Central State Archive of Rome the Author analyze the early attempts (1876) by G. U. Valentinis and G. Botti to apply the Pettenkofer method to Venetian and Parmesan paintings. The Pettenkofer technique (so called after the name of the Bavarian physicist who patented it in 1863) is based on the regeneration of deteriorated varnishes by means of exposure of paintings to alcohol exhalations. The process, improved by a large use of Copaiba balsam, was applied, as from 1886, to paintings in the Uffizi and in the Galleria Palatina in Florence. However, the state of conservation of these works should be scientifically examined, because paintings treated with Pettenkofer method have revealed modifications in the structure of the coats of paint, as recent researches by S. Schmitt prove. Such modifications are due to copaiba that, instead of affecting only the surface of paintings, gets into depth provoking structural detachments. In this way, preparatory layers as well as lower layers of paint tend to rise up to the surface, through the crackles of upper varnishes, because of their excessive and prolonged swelling.
