Study on latent sweat fingermark visualization on typical combustible substrates after instantaneous thermal exposure

Fingermarks are essential for identification, but the impact of instantaneous high-temperature gas explosion exposure on their visualization remains insufficiently understood, particularly for different combustible substrates and validation through full-scale explosion tests. This research developed a simulation platform for instantaneous thermal exposure (1200°C, 100-1000 ms) and examined six representative substrates: PVC window frames, PVC-coated corrugated and rubber hoses, PC switches, ABS gas alarms, and pine finger-jointed boards. Latent fingermarks were analyzed via macroscopic morphology, optical detection, fluorescent powder dusting and cyanoacrylate (CA) fuming, with quantitatively assessed by the CAST fingermark quality grading system. Results showed substrate thermal stability (pine < PVC < ABS < PC) affected morphology, but visualization success depended more on compatibility between surface state and detection principles.Optical methods were highly sensitive to surface roughening and charring, with effective durations (PC: 400 ms, ABS: 200 ms, PVC: 500 ms, pine: 300 ms) not strictly following thermal stability order. CA fuming failed on charred surfaces due to limited monomer diffusion, showing effective durations of 400 ms for PC, 300 ms for ABS and pine, and 500 ms for PVC. Fluorescent powder exhibited the highest tolerance (PC/ABS: 500 ms; PVC: 700 ms; pine: 600 ms), attributed to strong physical adsorption and fluorescence-based background suppression. Surface topography also proved critical: flat PVC allowed multiple methods, corrugations limited optical/CA efficacy, and ribbed rubber prevented all due to inadequate fingermark transfer.Full-scale explosion tests confirmed the substrate-fingermark visualization method interaction, offering scientific and technical support for fingermark recovery in gas explosion investigations.