How long does it generally take for Ninhydrin treated fingerprints to fully develop?

The correct timing for the development of fingerprints treated with Ninhydrin is several hours to several days. Ninhydrin reacts chemically with amino acids present in the sweat of fingerprints to produce a color change, leading to the development of visible prints. The optimal development process varies based on several factors, including temperature and humidity. Typically, a complete reaction can occur within 24 to 48 hours, but certain conditions may extend this period.

This means that, while you may see early results within a few hours, allowing time for full development is crucial, thus making several days a more accurate indication of the overall timeline for the complete drying and visibility of Ninhydrin-treated fingerprints.