The description of materials and methods addresses the reagents, the apparatus, sample preparation, and processing procedures. The reaction of OPA with latent fingerprint residues followed by treatment with a 1-percent nitric acid solution has been found to be sensitive, forming highly luminescent reaction products that can be visualized using the blue-green wavelengths of the argon laser as well as alternative light sources. It was also found that the OPA/nitric acid reagents might serve as a sensitive reagent for the post-ninhydrin or post-ninhydrin/zinc chloride treatment for latent prints. Development time at room temperature, however, can take 10-18 hours to achieve an intense luminescent print. The subsequent use of a steam iron (in steam mode) was found to accelerate the development time as it does with ninhydrin. The use of the steam iron in conjunction with the weak nitric acid solution seemed to often reduce the luminescent background formed by the OPA reagent or the paper substrate. The author advises that additional research should be conducted on the techniques described, especially concerning the finding of a replacement for freon. 5 figures and 7 references