Classification and uses of finger prints / by Sir E.R. Henry.

  • Henry, E. R. (Edward Richard), Sir, 1850-1931.
Date:
1913
Catalogue details

Licence: In copyright

Credit: Classification and uses of finger prints / by Sir E.R. Henry. Source: Wellcome Collection.

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    pressions, the following details must receive attention. The tin slab in use should be free from dust, hairs, or other foreign matter. It should be freshly cleaned each day, all traces of the ink previously used being removed. A very small quantity of ink should be applied, and this should be worked up into the thinnest possible film : unless the film is thin, the impression obtained will not he clear and sharply defined. From a finger so inked a good impression is secured, as even additional pressure will not do much harm. The paper used should be white and its surface not too glazed, for, unless it is sufficiently absorbent, nearly all the ink will remain on the finger, less adhering to the paper, the print resulting not being in consequence sufficiently dark. Good impressions can be taken on ordinary foolscap. Stress is laid upon the paper being white, so as to facilitate the work of photographing, should a photo- graph of the impression be, at any future time, required. Many kinds of ink have been experi- mented with, but, on the whole, printer’s ink is the most satisfactory, as it is procurable everywhere at trifling cost. The paper being porous absorbs the ink impressed on it by the finger, and, as the principal constituent of this ink is oily matter which readily oxidises under the action of the air, the sheets con- taining impressions may be at once handled without risk of defacement from smudging. The slab can be made of sheet copper or any other metal ; but as tin is the cheapest and most easily procured, it has been generally adopted. A “ plain ” impression is obtained by placing the