Ten pottery sherds from excavations in the area around Deruta (Perugia, Italy), having the typical "lustro" decoration, were analysed to establish their chemical composition. particularly that of the "lustro", and to gain mon insight into the procedure followed in making this decoration. The fragments, assigned to the 16th-17th centuries, were authenticated by thermoluminescence analysis (TL). Scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) was used to investigate the surface morphology and to determine the chemical composition of both the decorated surfaces and some incrustations. Fourier transform infrared spectroscopy (FTIR) was also used to characterise the incrustations. All fragments exhibited a similar chemical composition; the ''lustro'' is assigned to an ancient Spanish-Arabic formula. The incrustations were attributed to different origins; the reddish, iron-containing ones are due to residual lustro-paste, while the grey ones were produced by successive calcareous depositions. Reflectance fluorescence (RF) measurements, applied in situ, showed that different and easily recognisable emission signals are given by the "lustro", the blue design and the white glazed surface.