Abstract: The disclosure relates to a method of initiating a crystal growth prior to filtering off, from the mother liquor in which they were produced, of such crystalline explosives of the type hexogen and octogen produced by the so-called Bachmann process or variations of this process.According to the invention, the mother liquor is, after the end of the chemical reaction proper, subjected to a pressure-heat treatment which initiates the partial dissolution of the crystalline explosives obtained in the process, giving rise, after cooling of the mother liquor, to larger crystals which may more readily be filtered off.According to a further improvement of the invention a relatively pure octogen may be extracted from the mother liquor by way of a thermo-filtering of said liquor at a temperature of 60.degree.-110.degree. C.