What substance primarily makes latent fingerprints visible?

Latent fingerprints, which are the impressions left by the oils and sweat from a person’s fingertips, often require enhancement techniques to become visible for analysis. The primary method used to visualize these fingerprints involves the application of powders or chemicals that react specifically with the components found in the sweat or oils left by the fingers.

When powders are applied, they adhere to the oils and residues of the fingerprints, allowing the impressions to be seen against the background surface. The specific powders used may vary depending on the surface being examined, such as black powder on light surfaces or fluorescent powders for enhanced visibility under UV light.

Chemical methods can also be employed, such as using ninhydrin, which reacts with amino acids in sweat to produce a vivid purple color, making the fingerprints easier to see. Other chemical processes might include super glue fuming, which can cause fingerprints to become visible on non-porous surfaces.

While other substances, such as water and oil, play roles in the formation and initial presence of latent fingerprints, they do not typically make them visible in a forensic context. Blood, on the other hand, is not related to the visualization of latent prints; rather, it is a bodily fluid that can be used to establish the presence of a biological substance but