The ancient stained windows by Nicolò di Pietro Gerini in Florence. A novel diagnostic tool for non-invasive in situ diagnosis

Experimental data concerning an ancient stained window attributed to Nicolò di Pietro Gerini, Carthusian monastery, Galluzzo (Florence), are reported. The chromophores were identified non-invasively in situ by means of a spectro-analyser equipped with optical fibres. The novelty of the method consists in the use of the external solar light as a lighting source so as to increase the signal to noise ratio. Moreover, data on the chemical composition of the glasses and their alteration products, which were obtained from small fragments, are reported. Finally, a hypothesis about the origin of a colour change from blue to purple inside a pane is put forward on the basis of the spectroscopic results.