why do fingerprints cause smudges on surfaces such as glass?
In: Biology
Because the skin secretes small amounts of oil. There is more in some places than others, the forehead and the side of the nose for instance. Spend too much time with your hands in detergent and the oil gets washed away leaving you with dry feeling skin.
The oil from the skin is deposited in the shape of the fingerprint ridges. Criminal investigators will lightly dust an area with a fine powder and there’ll stick to the grease and turn the hardly visible “latent” print into one that can be photographed
Our skin carries oils and gunk through exposure or contact with the environment.
This is especially true for our nose as well as our fingertips. The smudges are leftover residue from water, soap, food, etc hidden in the grooves of your fingertips like trenches.
Fingers transfer oil normally from the hair onto a surface if the finger is moved across the surface it will create a smudge rather than a direct print.
When you touch something you leave behind oil from your skin. You can’t see it on darker colored things because it’s a light oil. Glass is clear making it easier to see light oils
Oily fingers cause the smudges
I mean a tiny number of skin cells also come off when you touch. But thats irrelevant and invisible
Imagine a fingerprint like a stamp and the pills and residue on the finger like ink. If you press the stamp into the ink and then carefully press it onto paper, you get a clear reproduction of what’s on the stamp. Same with a fingerprint.
If you drag and twist the stamp across the paper, you get a smudge. Same with a fingerprint causing a smudge after being dragged across a surface.
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