Abstract
IN certain libraries there exists a fixed rule that no books may be removed. This being so, all extracts and copies of plates and engravings have to be made in the libraries. Reproduction by the methods of ordinary photography is most inconvenient, since the employment of artificial light is strictly prohibited; also the introduction of a camera, and its manipulation in a library, are surrounded by many difficulties. These circumstances led me to devise the following method for obtaining copies of plates, engravings, printing and writing. A piece of cardboard is coated with a phosphorescent substance, and, after sufficient exposure to the light of the sun or of an arc lamp, it is placed at the back of the engraving or writing to be copied; on the face of the engraving or writing a dry photographic plate is placed, and then the book is closed for a certain time, depending on the nature and thickness of the paper used in the book. I find that the period of time lies between eighteen and sixty minutes. The plate is then withdrawn and stored in a dark box for development. The dry plate is easily manipulated under a cloth, which shuts off all light and covers the book during the operation. The results are sufficiently good for most purposes—in the case of some papers the fibrous structure is shown; this very slightly detracts from the clearness of the copies made by this process. Neither the luminous substance nor the dry plate injure the bdok in any way, so that the method may be employed in the case of valuable prints and engravings (Fig. 1). IF films be used instead of plates, a large number of copies of different engravings in the same book may be made at the same time. The time of exposure to the phosphorescent backing is shortened considerably by placing the phosphorescent card on a warm surface, such as that of a metal vessel, heated to about 20° C. with hot watery when films are employed, this temperature should not be exceeded. In an experiment made in the laboratory I found that the phosphorescent substance under normal barometric pressure became brightly luminous when sub jected to the brush discharge of a Tesla inductor; the discharge from an ordinary induction coil fails to produce the same effects.
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JERVIS-SMITH, F. Phosphorescence as a Source of Illumination in Photography . Nature 63, 421 (1901). https://doi.org/10.1038/063421a0
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DOI: https://doi.org/10.1038/063421a0