A validation study was next undertaken using 80 one-day-old natural fingermarks sourced from three donors and placed on both tile and painted gyprock surfaces. Each of the three donors contributed ten to twenty fingermarks per surface in batches of ten. All fingermarks were aged by 24 hours prior to treatment. Using the modified CAST grading scheme (Table ), average scores for the blended HFE-7100 spray across all developed prints were 2.89 and 2.75 for gyprock and tile respectively. For both surface types, the most common outcome was between full and two thirds development (gyprock, 55%; tile, 45%), with complete development showing contiguous ridge patterns observed less often (gyprock, 18%; tile, 25%). While tile yielded more fully developed fingermarks, this surface also yielded more fingermarks with less than one third total development, (gyprock, 3%; tile, 17%). It is possible that being a true nonporous surface, fingermarks on tile were more exposed to degradation from environmental factors, yet also more accessible to the developer spray, leading to the observed variability in visualisation quality seen.