The purpose of this study was to initiate a survey of chemical ageing processes for two selected home-made explosives (HME). The underlying question is to which extent environmental factors such as temperature, relative humidity and UV exposure affects ageing processes, and if they do, to which extent these processes are predictable given that the environmental circumstances are known. On the longer term, this knowledge can be used for exploitation purposes, e.g. to determine the age of an HME find from its chemical degradation. This report contains a description of the work carried out after the release of the report FOI-R--4033--SE. The work was now focused on the primary explosive hexamethylenetriperoxidediamine (HMTD), as this was the substance that had shown changes upon ageing. Since study in 2014 had inadequate control of climate parameters, parts of it were repeated with the same control parameters. Then a modified method to control moisture was applied, so that stable conditions were obtained. The ageing study lasted for three months in both cases. At the beginning and the end of this period, the samples were weighed and analysed by means of Raman spectroscopy. Also this time significant, aging-related changes were observed. This study shows that HMTD is susceptible to environmental ageing. The magnitude of this effect varies depending on the environment.