Incorporation of silver ions into undoped and doped lead crystal glass was performed by ion exchange. Polyvalent arsenic, antimony, cerium and tin oxides, used as thermoreducing agents, were added in different weight percentages to the starting lead crystal glass. Thus, several doped lead crystal glasses were obtained by conventional melting. The role of the polyvalent oxides as reducing agents of silver ions introduced by ion exchange was studied by focussing on analysis of diffusion depth profiles obtained by SEM-EDX and direct observations performed by TEM. The optical absorption behaviour of the samples was studied to clarify the influence of the parameters involved in the ion exchange process. Chromatic coordinates were calculated from the corresponding transmission visible spectra. The influence of the nature and concentration of the polyvalent oxide dopants on the formation, size and aggregation of silver colloids is discussed Experimental parameters affecting the ion exchange treatment were varied and optimised to obtain silver colloids suitable to produce yellow and red ruby colouring in the undoped and doped lead crystal glasses, respectively. The most intense red ruby colouring was obtained with antimony doped lead crystal glasses, which were the most efficient at reducing silver ions and forming nanosized metallic colloids. Temperature, silver nitrate concentration in the molten salt bath and duration of the ion exchange treatment affect the size, aggregation and distribution of the silver colloids generated It has been demonstrated that ion exchange is a suitable process to obtain superficial ruby lead crystal glasses. In such glasses the synergic presence of both silver and a polyvalent oxide dopant favours the formation of metallic particles responsible for the ruby colouring. [ABSTRACT FROM AUTHOR]