The principle of the method specified is spraying the extract solution into the flame of the burner of an emission or absorption spectrometer, if necessary with the addition of a spectrochemical buffer solution, or into the flame of a filter flame spectrometer without this addition. For FES and FAAS, the lines at 589,0 nm and 766,5 nm, respectively, are used and compared with the measurements of reference solutions, for a flame filter spectrometer, the specific filters are used. Measures the concentrations of sodium and potassium, expressed as their oxides Na2O and K2O. Applies to the analysis of extract solutions obtained from any kind of glass or glassware.