The Photographic Sabatier Effect William L. Jolly University of California. Berkeley, CA 94720 Thedevelopment ofexposed photographic film or paper is generally carried out in romplete darkness or under a safelight t o which the film or paper is insensitive. Therefore, the idea of purposely exposing a photographic emulsion to ordinarvlieht - " during the develooment orocess mav seem .oreoos. terous-one miiht expect eompletk fogging (61ackening), or at least severe darkening. of the develo~edimaee. However. the regions of the photographic emulsion that undergo even the slightest darkening durina the first staw of development are somewhat desensitized tdward furtherexposure to light, and therefore the film or paper is not entirely darkened after the second exposure to light. Such intentiinal exposure to light during drvelopment is the hasi3 of a process long used by photographers to introduce both positive and negative character into developed images. The phenomenon, discovered in 1857 by an Englishman named William Jackson (I)
and popularized by a French doctor named Sabatier ( 2 ) ,is known in technical circles as the Sahatier effect. However, we shall refer to it by the term now used by most practicing photographers, namely solarization. Unfortunately, the word solarization has a second. older meanine in ohotoeraphy (the reversal obtained by the ordinary developmen; of certain emulsions when extremelv overexoosed). but there is generally no confusion due to these diiferent'uses of the word. Not too long ago many photographers were convinced that solarization is a orocess that cannot be reoroduced. that successful results'are a matter of chance, and that the process isassocinted with a sort of mysticism. These misronce~tions arose probably because more variables must be cohtrolled in the solarization process than in normal photographic development. If all the variables are not kept
Figure 1. A normally developed print and the corresponaing solarized print. Note the tine white lines (Mackielines)outlining the Washington Monument and the main tree branches in the solarized version. (Photos by author.)
Volume 68
Number 1 January 1991
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constant, the results are of course not constant. However, in recent years, photographers have learned how to obtain consistently good results in solarization, and the technique is now just one of the standard methods for modifying prints (methods including dodging, flashing, toning, etc.). Indeed, with appropriate care, the phenomenon can he reliably demonstrated to groups of students in a darkroom, a darkened laboratory, or even a lecture hall. Consider the steps in a typical solarization of a black-andwhite print (3).First, the photographic paper is exposed to light through a negative, using either an enlarger or a contact-printing frame. The paper is then placed in a tray of developer solution and gently agitated. An image usually begins to appear after about 25 s and gradually darkens as development continues. After about 50 s, when the image is fairly well defined but considerably lighter than a fully developed image, a white light is turned on over the developing tray for several seconds. Soon remarkable changes begin to take place. The parts of the printthat had developed to some extent (that is, the black and gray regions) undergo practically no further change. However, the remaining regions of the print (that is, the regions that were white or very light gray and had received no or very little exposure) darken in approximately inverse proportion to the original exposure
under the enlarger. These changes in the print are spectacular; indeed, the effect wasdescribed by Sabatieras6'themost surprising phenomenon of which one is able to he witness." After ahout 1 min of development after the second exposure, the print is transferred to the acid stop bath (to stop development) and then to the fixer. The print is then washed and dried in the usual wav. A photographic print developed in the ordinary way can he comoared with its solarized version in Fieure 1. In t
