How long do fingerprints stay on paper? Ask god for help

Fingerprints on paper can be revealed by chemical methods in a few years.

Generally speaking, fingerprints can be kept in restaurants for several days, indoors for several weeks and on mirrors for more than one month, especially in combs and safes.

If fingerprints are left on the surface of absorbent articles such as paper, cards, leather and wood, they must be chemically treated before they can appear in the laboratory.

With the development of laser technology, China uses laser to display fingerprints. The display device adopts argon ion laser. Laser can show fingerprints, because there is always a layer of sweat and fatty acid on the surface of people's fingers, leaving inconspicuous fingerprints after touching objects; Use laser, sweat, fatty acids, etc. There will be color fluorescence and clear fingerprints. Take a clear fingerprint photo with a special fingerprint camera. After the photo is enlarged, it brings a lot of convenience to the appraisal work.

Extended data

Fingerprint has the characteristics of "life-long invariability and uniqueness". Long ago, people identified themselves with handprints on paper or boards. Fingerprint has been widely used in entry-exit inspection, searching criminals and other fields. Fingerprint is a kind of dermatoglyphics, which is formed by the linear arrangement of protrusions and depressions on the epidermis.

The inner sides of human hands and feet are covered with dermatoglyphics. Fingerprints are widely used in searching criminals and other fields to identify people. As we all know, ancient Babylonians and China used fingerprints to verify people's identity a long time ago.

In principle, a person's fingerprints are lifelong. After the child grows up, the fingerprint only becomes bigger and thicker, and the characteristics such as the shape and quantity of the lines remain unchanged.

Baidu Encyclopedia-Fingerprints (lines on people's fingers)