Constantina P. HADJIANTONIOU-MAROULIS and Apostolos J. MAROULIS Aristotle University of Thessaloniki, Department of Chemistry THE CHEMISTRY OF PHOTOGRAPHY IN FULL DAYLIGHT Received: 21 September 1999; revised: 22 December 1999; accepted: 22 December 1999 ABSTRACT: Photography, the daughter of art…

The visualization of the latent image during development constitutes the most magical part of the photographic process ever since its invention a century and a half ago. From the time of the making of the motion picture “Blow Up” by Michelangelo Antonioni, movie-makers in particular capitalized on the intriguing power of photographic image development. The same motives, no doubt, underlined the making of the instant photography machines in the early seventies (the SX-70 Polaroid-land family of photographic cameras, and their Kodak counterparts) which were, and still are, capable of furnishing a picture which develops in front of our own eyes in broad daylight. Chemical educators resort to photography-related experiments for the purpose of demonstrating either photochemical principles (Sasaki, 1992; DiSpezio, 1987) or the reductive power of certain organic compounds such as dihydroxybenzenes (Neubauer, 1997) or paminophenol (Rothenberger, 1991) on ionic silver. In particular, they employ black and white photographic paper, which upon contact with an alkaline solution of hydroquinone or some other reducing agent, turns black due to the reduction of the silver halide contained in its emulsion into black metallic silver. Because such an experiment, however instructive, lacks the above mentioned magic of the photographic process, we developed an alternative procedure which utilizes a “bleached out” black and white photographic image in the place of the ordinary photographic paper. The bleached out paper can be developed using organic developers, in full daylight, yielding full tone photographic images. EXPERIMENTAL PROCEDURE. SAFETY NOTE: Nitric acid can produce very toxic nitrogen oxides; therefore, fumes coming from nitric acid spills are hazardous. Solutions of nitric acid can destroy eye or skin tissues. Hydroquinone is moderately toxic and it primarily affects the eyes. The use of safety goggles and gloves is strongly recommended. In case of contact with either of these chemicals, immediate wash of the affected part with large quantities of water is necessary. A black and white photograph is immersed in a tray containing a warm aqueous solution (40° C) of 1:1 nitric acid to which 4.0 g/100 mL of potassium bromide was added. While the bleaching of the silver image starts after a few seconds (the bleaching of a resin coated paper takes about 1 min), the print…

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