Importance

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Abstract

A first method of revealing a fingerprint involves the charging of the surface bearing the fingerprint to a high electric potential and applying finely divided carbon to the charged surface to form a pattern thereon corresponding to the fingerprint. The finely divided carbon may be dusted or sprayed on or may be in suspension in a dielectric liquid into which the charged surface is introduced. In another method the surface is charged while submerged in the dielectric liquid, under the action of an electric field in the dielectric. In another method an electrically charged sheet is brought into contact with a surface bearing a fingerprint and after being removed, the charged sheet has applied to its surface finely divided carbon which adheres thereto depending on the charge pattern remaining thereon after contact with the fingerprint. The pattern of finely divided carbon can be fixed in position by applying thereover a transparent protective layer.

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First Claim