Sol–gel silver containing coatings have been prepared and applied upon lead crystal glass. Both undoped and arsenic oxide-doped lead crystal glasses have been used as substrates. Arsenic oxide was introduced with different percentages as a thermoreducing agent, with the aim to favour silver ions reduction and aggregation to form nanosized colloids. Such silver colloids yielded a superficial yellow ruby colouring, due to their known surface plasmon resonance band in the visible range (∼420 nm). The influence of the experimental parameters to obtain yellow ruby colouring (percentage of arsenic oxide in the lead crystal base glass; silver content of the coatings precursor sol; coating thickness; atmosphere, temperature and time for thermal densification; etc.) were investigated. Samples were studied by transmission electron microscopy and optical spectroscopy (absorption and transmission). Colour co-ordinates, dominant wavelength and colour purity percentage were calculated from the corresponding transmission visible spectra. The role of the thermoreducing dopant (arsenic oxide) is essential for obtaining superficial yellow colouring. The higher the percentage of arsenic oxide, the higher is the intensity of the yellow colouring. When the silver content of sols increased, the same tendency is observed. Thermal densification of the sol–gel coatings have to be carried out under oxidising atmosphere, since heat-treatments performed under reducing atmosphere yielded grey-brownish colouring, due to reduction of the lead from the base glass. Optimum conditions for obtaining superficial yellow ruby colouring on lead crystal glass were selected.
