The use of space resources will play a vital role in sustaining a permanent human presence on the lunar surface. In Situ Resource Utilisation (ISRU) is expected to underpin the sustainability of such current and future missions. Water ice at the lunar poles in Permanently Shadowed Regions (PSRs) could provide a source of water for habitat replenishment or as rocket propellant. The water ice in PSRs is likely to be preserved at < 110 K and at least at one polar location, it has been directly measured at 5.6 ± 2.9 wt. % [1], [2]. Rocket propellant can be used to resupply satellites in cislunar space and transport crew and cargo from the lunar surface [3]. The exact nature of water ice stored at PSRs is currently unknown; however, it is likely to be mixed with the local regolith. Thus, finding a technique that maximises the water ice extraction as quickly as possible will be crucial given the harsh conditions present in a PSR (no direct solar irradiation, < 110 K, vacuum conditions). Previous work has found microwave heating to be an efficient technique for extracting water ice from icy lunar simulants [4], [5]. This work presents further microwave heating experiments where, through the use of a Dynamic Mass Instrument (DMI), unique features in the mass loss profiles of Diffuse Icy Regolith (DIR) and Granular Icy Regolith (GIR) were identified. These unique features infer where and for how long microwave heating is an effective water extraction technique.