Techniques Used to Develop\ Fingerprints and Procedure for Collecting Them

            Fingerprints can be left off of two types of surfaces: Non-Porous and Porous

Non- Porous

Prints left on non-porous surfaces such as glass, mirrors, plastic surfaces, and paint. In order to recover those prints the use of dusting is required.

Dusting- Area of the print is lightly dusted with a colored powder depending on the background. The dust is lifted with tape and set against a contrasting background.

Black dust: White Surfaces

Grey Dust: Dark Surfaces

Fluorescent Dust: Multi-Colored Surfaces

Magnetic Dust: Leather or Rough Surfaces

Porous

Prints left on fiber-like surfaces such as paper, money, and cloth are called porous. In order to recover those prints the use of chemicals is necessary. The various chemical methods of recovering fingerprints are Iodine Fuming, Ninhydrin, Silver Nitrate, and Super Glue Fuming.

Iodine Fuming—Material is placed in an enclosed cabinet along with iodine crystals. The crystals will heat up and will soon turn into gas vapor. The vapor would then cause the prints to appear.   

Ninhydrin- the chemical is sprayed on the surface of the material via an aerosol can. After an hour or two, the prints begin to become visual, however the process can be accelerated if the prints are heated up after application.

Silver Nitrate-Last resort when both Iodine Fuming and Silver Nitrate are unsuccessful. The silver nitrate is sprayed on the surface of the material and is left to dry. Then it is exposed to ultraviolet light, which exposes the prints.

Super Glue Fuming (also used on non-porous materials)-Glue is placed on cotton and treated with sodium hydroxide. Fumes are then created by heating the cotton; the fumes and object are placed inside a heated chamber for up to six hours and the fumes adhere to the print, exposing it.

Example of a fuming chamber