The colour of silver stained glass - analytical investigations carried out with XRF, SEM/EDX, TEM, and IBA

Glass treated on its surface with silver compounds and an aluminosilicate, such as ochre or clay, at higher temperatures (between 550 and 650°C) accepts a wide variety of a yellow colour. It is the aim of this study to investigate the parameters of the manufacturing process affecting the final colour of silver stained glass and to correlate them with the final colour and colour intensity. Therefore, defined mixtures of ochre and a silver compound (AgCl, AgNO₃, Ag₂SO₄, Ag₃PO₄, Ag₂O) were prepared and applied on soda-lime glass. The firing process was modified within the range from 563 to 630°C and glass samples were analysed after treatment with energy dispersive X-ray fluorescence analysis (EDXRF), scanning electron microscopy (SEM/EDX), transmission electron microscopy (TEM), as well as ion beam analysis (IBA) with an external beam. Within the scope of IBA simultaneous measurements using particle-induced X-ray emission (PIXE), particle-induced gamma-ray emission (PIGE), and Rutherford backscattering spectrometry (RBS) were carried out in order to obtain the thickness of the Ag-rich surface layer and the depth distribution of Ag. By means of TEM the microstructure of the silver particles was visualised. XRF results show that the lowest amount of Ag could be detected on glass samples treated with silver stain mixtures containing AgCl and Ag₂O. A low kiln temperature (e.g. 563°C) results in a higher silver concentration at the surface and lower penetration depths. Furthermore, the results obtained with SEM/EDX at cross-sections of the glass samples could be confirmed by PIXE, PIGE, RBS, and TEM.