D.F.O. (1,8-Diazafluoren-9-one) Crystals are used to develop latent prints on porous surfaces. D.F.O. reacts to the amino acids present in a latent fingerprint. The resulting prints will fluoresce with the use of a forensic light source. D.F.O. may be applied by either dipping or spraying. After processing with D.F.O., the development may be accelerated with heating. The item must be dried, then placed in a heating chamber set to approximately 212°F for 20 minutes, or heated with a standard dry clothing iron (no steam). EVIDENT provides D.F.O. as a powder reagent.