This part of ISO 4802 specifies: a) methods for determining the hydrolytic resistance of the interior surfaces of glass containers when subjected to attack by water at (121 ± 1) °C for (60 ± 1) min. The resistance is measured by determining the amount of sodium and other alkali metal or alkaline earth oxides in the extraction solution using flame atomic emission or absorption spectrometry (flame spectrometry); b) a classification of glass containers according to the hydrolytic resistance of the interior surfaces determined by the methods specified in this part of ISO 4802. The test method specified in this part of ISO 4802 might not be applicable to containers whose surfaces have been treated with silicon (e.g. containers that are ready for direct filling).