EVALUATION OF TIN OXIDE COATINGS ON GLASS CONTAINERS USING HECM AND EPMA

The paper describes the principles of operation and the accuracy of th e hot end coating meter (HECM) an instrument for production control wh ich measures the surface reflectance of containers and correlates its results with the microanalytical determinations of tin oxide performed with electron probe microanalysis (EPMA). The parameters which influe nce the readings of the HECM are illustrated on the basis of mathemati cal simulations and verified experimentally on containers industrially coated with tin oxide. Suggestions to improve the measurement accurac y are provided. A Monte Carlo procedure for calculating the tin oxide coverage from microanalytical determinations is described. A compariso n between HECM and EPMA shows that their results are linearly correlat ed in the whole range of industrial interest and that 1 CTU correspond s to 0.13 mu g SnO2/cm(2). The correlation between the two techniques is not affected by the coating temperature and by the annealing condit ions.