Factor Influencing Fingerprint Powder Quality
There are several factors influencing the effectiveness of fingerprint powders.
- Fineness
- The powder must be fine enough to show the detail of the fingerprint. Finer powders would be theoretically capable of displaying greater detail than coarser powders.
- Adhesion
- The powder must display the right level of adhesion, so that it will adhere to the residue of the fingerprint (often oils) and not adhere to the rest of the surface where it would obscure the view of the print. When a powder coats a surface, this is known as 'painting'.
- Sensitivity
- Sensitivity is related to adhesion, and is how well the powder adheres to a surface. For example, aluminum flake is more sensitive than aluminum powder, but greater sensitivity is not always desirable.
- Color
- The fingerprint powder must be a suitable color for the surface in question.
- Flow
- To a lesser extent, it is important that the powder can flow, and does not 'cake' into a solid block, which would render it useless.
As these various qualities are not normally all present in any one material, compositions of various materials are generally used. For example, lampblack is particularly black in color, absorbing around 98% of incident visible light, but other materials may have greater adhesion, or flow more effectively, producing a better overall powder than either alone.
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