Figure 4. Height distribution from the right side of the degrading bloodstains at various timepoints (in minutes). The designated bin width was set to 5 µm.
Additionally, we observe a high degree of variance in the number of observed cracks and pits; generally, for all stains, they increase rapidly for the first 30 minutes and then they plateau (Figure 5). Typical minute cracks around the edge of the bloodstain were not detected by the profilometer, making it difficult to assess when crack formation and propagation began, but it can be approximated to be ~15-20 minutes after deposition. Larger cracks located towards the centre of the bloodstain appeared around 20-25 minutes after deposition; surface average roughness values at these times slightly increased. Earlier time points also contained more cracks and pits with smaller areas which subsequently increased over time, leading to cracks with larger areas at later time points (Supplemental S4). There does not appear to be a volume dependence in this study as there is a high degree of variance observed in these data.