Optical Microscopy, transmission & reflection infrared spectroscopy, contact angle & weight loss on annealing are used to establish the thickness & homogeneity of the organic coatings used industrially to lubricate glass containers. As shown by a range of experiments & mathematical simulations, infrared spectroscopy is suitable to detect in situ the C-H bands of the hydrocarbon material near 2900cm-1 & to quantify organic coverage. Useful results are obtained using a FTIR spectrometer equipped either with a specula reflectance accessory or with an infrared microscope. Due to the different size of the area analysed (about 1cm vs 1 x 10-4 cm2), the first setup is suitable to monitor average coverage, the second to check local distribution. Other absorption bands of the coating, particularly those associated with the carbon oxygen bonds & potentially suitable to provide information on the organic-to-glass, are too weak to be detected. The study provides for the first time an estimate of the thickness of the cold end coating (generally within 100nm) and highlights their inhomogenous distribution and patchy structure.
