Chapter 1. Early History and General Procedures

Early History of the Sabatier Effect

In the very early days of photography, when daguerreotypes and calotypes were the only kinds of photographs made, photography was used mainly by artists, professional portraitists, and scientists. However, after the invention of the wet plate, or collodion, process in 1851,¹⁰ photography boomed in popularity and began to be practiced by many amateurs. In Europe and America these "lovers" of the art, together with professionals, formed photographic societies and clubs that held regular meetings and published journals in which noteworthy findings of the members were reported. On the pages of these journals are found descriptions of many interesting experiments and lucky accidents carried out in the darkrooms of these early photographers.

On September 4, 1857, a Mr. William Jackson,¹¹⁸ of Lancaster, England, sent a letter to the editor of the Journal of the Photographic Society of London entitled "On a Method of Reversing the Action of Light on the Collodion Film, and Thereby Producing Transparent Positives." In this letter, he described how he obtained direct positive transparencies by allowing diffused daylight to fall on the plates as soon as the image appeared after pouring on the developer. He warned that some practice was required to find the precise point of development appropriate for making the exposure to diffused daylight, and he pointed out that in order to avoid skies appearing as negative images, some shielding of the sky areas during the exposure was necessary. As far as I know, Jackson was the first person to describe this amazing phenomenon, now known as the Sabatier effect or, in nontechnical circles, as solarization.

In those early days, almost all of photography was mysterious or poorly understood, and many photographers considered Jackson's process to be no more remarkable than the normal development of collodion plates to produce negative images. Photographers didn't know enough about photography to appreciate fully the unusual character of the Sabatier effect. However, today the situation is different. Modern photographers are conditioned to the need for developing exposed photographic film or paper in complete darkness or under a safelight to which the film or paper is insensitive. Most photographers consider the idea of intentionally exposing a photographic emulsion to ordinary light during the development process as preposterous; they expect such exposure to produce complete fogging (blackening), or at least severe darkening, of the developed image. The fact that complete darkening does not occur and that a positive image does develop makes the Sabatier effect a magical process that never ceases to amaze and entertain even old hands at the process. Thus the effect is probably more amazing today than when it was first discovered.

Some of those who heard the reading of Jackson's letter at the 1857 meeting of the Photographic Society were duly impressed. During the discussion following the presentation, a Mr. Fenton (probably Roger Fenton, the first secretary of the Photographic Society, who photographed the Crimean war in 1855^32,190) remarked "I have often found, on taking a picture during development into the open sunlight, that a positive picture has been produced, but I have always found it has been impossible to produce a constant result - that when I have taken a picture out and developed it, that one- half has been positive, and the other half an intense negative. I do not think it of the slight importance which some seem to imagine, and hope that Mr. Jackson will carry out his experiments still further."⁸³ During the following decades, various other photographers, apparently oblivious of Jackson's work, reported their rediscovery of the phenomenon, or similar phenomena. ^{21,69,70,115,192,204,206} Some photographers even reported direct positive formation after darkroom manipulation without a second exposure to light, but it seems likely that most, if not all, of these processes involved inadvertent exposure to daylight in the darkroom and that the positive images were due to the Sabatier effect.^{7,195,202,203,205,209} Some photographers confused the Sabatier effect with an entirely different phenomenon: solarization due to overexposure (to be discussed soon).^60,70,175 Because of this confusion, the word solarization acquired an ambiguity that persists to the present day.

There appears to be no reason for crediting Sabatier with the discovery, or the first description, of the effect which now bears his name. In 1862, Sabatier did describe the effect and implied that it had never before been described and, further, that he was the discoverer.^204,206 Yet as early as 1860, he must have been aware of the previous work. In the introduction to Sabatier's first contribution to the French Society of Photography, published in Cosmos in 1860,²⁰³ the recording secretary stated that "Undoubtedly Mr. Sabatier has fallen on an idea that Count Schouwaloff communicated to the French Society of Photography at its meeting of October 21, 1859." In that communication,²⁰⁹ Schouwaloff said "I remember having read somewhere that one obtains effects of this type (reversals) by exposing the collodion to light during the development." Sabatier chose to ignore these remarks.

At least we can credit Sabatier with an effective advertising campaign for the process. In his second 1862 publication²⁰⁶ he wrote glowingly: "Only two conditions are thus essential, and these are so simple to fulfill that all photographers who are not hindered by industrial preoccupations and are aware of the charms of science or of the art which it cultivates, will be eager to experiment, will wish to see with their eyes and to touch with their fingers, the most surprising phenomenon of which one is able to be witness."

Sabatier's name is often misspelled. In his first article, published in 1860 in Cosmos,²⁰³ his name is given as Sabatier. When this article was abstracted in the 1860 volume of the Bulletin of the French Society of Photography,²⁰⁵ the spelling was changed to Sabattier. This abstract is commonly cited and is probably responsible for the frequent misspelling of his name. In the first of his two 1862 communications, his name is spelled Sabatier; in the second, Sabattier. Probably the recording secretary of the society was responsible for the second misspelling.

In Sabatier's first article, he is described as a doctor of medicine from the village of Saint- Mammers, near Moret, in the province of Seine- et- Marne, France (about 40 miles from Paris). It is stated that he was a student of entomology and an amateur photographer. Various authors have confused him with another gentleman, Dr. Armand Sabatier. The latter Sabatier was a distinguished scholar who spent much of his life as a marine zoologist at a zoological station in Cette, on the Mediterranean.^186,187 There are several facts that show that the Sabatier of Saint- Mammers and Armand Sabatier were different people. (1) Armand Sabatier served as an intern in a hospital in Lyon (southern France) from 1858 to 1861, exactly the interval during which the Sabatier of Saint- Mammers was active in the French Photographic Society in Paris and practicing medicine. (2) Armand Sabatier's publication list includes nothing on photography. (3) Armand Sabatier was not yet a full- fledged doctor in 1860, when the Sabatier of Saint- Mammers was a doctor of medicine.

Oddly enough, a man named Jean- Baptiste Sabatier was active as a daguerreotypist in Paris during the years 1842 to 1870. However, he definitely was not the Sabatier of the Sabatier effect.⁵⁷ Not only did he reside in Paris (not Saint- Mammers) during the period around 1860, but also he was never a doctor. Regrettably, we must conclude that we know almost nothing of the background, and not even the first name, of the man after whom the Sabatier effect is named.

Although most of the early work on the Sabatier effect was done using collodion plates, at least one person noticed the effect with the old waxed paper Calotype process. This photographer, using the pen name Rho Delta, wrote as follows in 1863:⁷⁰ "About six years back, when using the waxed paper process, ... a negative I was developing began to come out so foggy and bad that I took it from the bath and threw it into the open air. It caught my eye by accident two or three minutes afterwards, when, to my great surprise, it was developing into a positive so beautiful in half- tone, and other artistic qualities, that I have never seen anything in photography to equal it. I tried anxiously to fix it, but all the beauty disappeared in the hypo as rapidly as it had been developed." After the invention of dry gelatin plates during the 1870s,¹⁹¹ photographers found that gelatin emulsions showed the effect as well as collodion emulsions, and, of course, gelatin emulsions have been used almost exclusively ever since.

Other Kinds of Solarization

Overexposure Solarization. -
With ordinary photographic materials, increasing exposure results in increasing density. With some materials, however, there is a point beyond which further increase in exposure results in reduced optical density. The first use of the word solarization was in reference to this phenomenon, which, however, is phenomenologically and mechanistically different from the Sabatier effect, or Sabatier solarization. This first type of solarization, which we shall refer to as overexposure solarization (to avoid confusion with Sabatier solarization), was even observed in highly overexposed regions of daguerreotypes.

In 1840 John W. Draper, a professor of chemistry and one of the first Americans to use daguerreotypy, described the precautions to be taken when making a portrait:⁷² "A person dressed in a black coat, and open waistcoat of the same colour, must put on a temporary front of a drab or flesh colour, or by the time that his face and the fine shadows of his woollen clothing are evolved, his shirt will be solarized, and be blue, or even black, with a white halo around it. Where, however, the white parts of the dress do not expose much surface, or expose it obliquely, these precautions are not essential; the white shirt collar will scarcely solarize until the face is passing into the same condition." The blue color of overexposure solarization was fortunately not very detrimental when it occurred in daguerreotypes of outdoor scenes, in which the sky was rendered blue. Indeed, such solarization, combined with the various shades of brown found in some daguerreotypes, gave many early daguerreotypes a beauty rivalling that of modern color photographs.

Figure. 1.1 An early French daguerreotype showing overexposure solarization. Note the dark border lines on the right sides of the arms. [This reproduction shown in J. Buerger, "French Daguerreotypes," U. of Chicago Press, 1989.]

A similar type of solarization was also observed in grossly overexposed silver halide print- out images. For example, in 1858 Craddock⁵⁴ reported: "While making experiments on the operation of light on iodized paper, I exposed a piece of negatively prepared paper under a small engraving for two hours, in a bright summer sun. On removing the engraving, I was surprised to see a positive- looking copy."

Platinum and palladium prints also show overexposure solarization. These prints are made by contact- printing negatives onto specially- coated paper with sunlight or ultraviolet lamps. When the printing exposure is excessive, those regions of the print that receive the most exposure can end up with a lower density, and a somewhat more golden color, than regions that receive slightly less exposure. The effect is markedly affected by the composition and concentration of the light- sensitive coating on the paper and by the temperature and humidity during the exposure.^183a

The early silver halide- gelatin emulsions (in which the image was revealed, of course, by development) were easily solarized by overexposure. Two famous examples of prints made from partly solarized negatives are the Black Sun prints of Ansel Adams¹ and Minor White.¹⁶³ In each of these prints, everything is normal except the disk of the sun, which is dark gray. Adams claimed that the reversal was anticipated and previsualized. White admitted that, in his case, it was an accident and rhapsodized, "The sun is not fiery after all, but a dead planet. We on earth give it its light."

Modern photographic emulsions generally do not show this phenomenon of overexposure solarization. However, Kodak sells Professional B/W Duplicating Film and Rapid Process Copy Film, which are designed to make negatives from negatives and positives from positives with conventional processing. It is possible that these films have been given a uniform preexposure and that they are based on overexposure solarization. It is also possible that they have direct positive emulsions of the type discussed in Chapter 5 under Emulsions with Mainly Internal Sensitivity Sites.

Figure 1.2 The Black Sun photograph of Minor White, 1955. The camera shutter was so cold that it operated too slowly, causing severe overexposure and reversal of the sun's image. [From Time-Life's "Great Photographers," ref. 163, p. 185.]

It is easy to understand why many of the early photographers confused Sabatier solarization with overexposure solarization. After all, in both processes, reversal occurs as a consequence of extra, beyond- the- normal, exposure. It was not always appreciated that a gross overexposure before development gives an entirely different result from a weak exposure during the development process. However, Brothers,³¹ in his 1892 book on photography, clearly distinguished the effects. He referred to the Sabatier effect as "pseudo- solarization," a designation that has been used occasionally even to the present day.

Around 1929, Man Ray rediscovered the Sabatier effect with his assistant, Lee Miller.*

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* See Chapter 3, under Man Ray and Lee Miller, for details of this rediscovery.

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He exploited this technique in much of his photographic work for the next eight years or so and must be credited with popularization of the term "solarization" for the Sabatier effect. Consequently, the word solarization has little ambiguity when used by amateur and fine- art photographers; to most the word signifies only the Sabatier effect. Ambiguity is much more probable in discourse with photographic scientists, who are more likely to be aware of, or concerned with, overexposure solarization. As used in the remainder of this book, the unmodified word solarization is synonymous with the Sabatier effect.

Luppo- Cramer's Variations. -

Luppo- Cramer has described two "solarization" processes that correspond neither to overexposure solarization nor to Sabatier solarization. Although these processes will probably never again be used, I describe them for the sake of completeness. First, he described a "variation" of the Sabatier procedure in which an exposed glass plate is given a rather short development and, without rinsing, exposed to daylight through the glass side of the plate.¹⁶⁶ Within a period of 30 to 60 seconds, the image undergoes reversal, as viewed by reflection from the glass side. Luppo- Cramer explained this effect as being partly due to the depletion of the developer in the upper layers of the emulsion in the image regions of high initial exposure. Thus in such regions, the undeveloped emulsion near the glass has a very low concentration of developer at the time of the second exposure, whereas in regions of low initial exposure, the entire emulsion has a high concentration of developer. Presumably the reversed image disappears somewhat upon treatment with fixer, because the light regions of the image are made of silver bromide, which dissolves in fixer.

The second unusual effect described by Luppo- Cramer was based on the formation of a strongly colored fog on unexposed plates, probably due to improper storage conditions.¹⁶⁷ When such plates were exposed and developed, the colored silver in the unexposed part of the image sometimes had greater covering power than the normally- developed black silver. Luppo- Cramer referred to the apparent reversal as pseudosolarization.

Border Depletion Solarization. -

This relatively new technique produces prints with white border lines similar to those formed in the Sabatier effect, but based on an entirely different principle. The typical procedure involves development in the presence of a silver complexing agent (to remove undeveloped silver halide near boundary areas) followed by exposure to bright, diffuse light. The general method is discussed thoroughly in Chapter 6.

Technical Description of the Phenomenon

If a sheet of photographic paper is exposed through a step tablet, thus creating a series of zones with gradually increasing exposures, normal development produces a print like that shown in Fig. 1.3A. If a similarly exposed piece of paper is solarized (that is, exposed to diffuse light for a short time during the development process), a print like that shown in Fig. 1.4A is produced. The corresponding H and D plots (plots of density vs logarithm of initial exposure) are shown immediately above the step- tablet prints, in Figs. 1.3B and 1.4B. It can be seen that, in solarization, the second exposure causes increased density in all the zones that received very low, or no, initial exposure.

Figure 1.3 A normally-developed step wedge and the corresponding H and D curve. BroviraSpeed No. 4 paper and 1 + 1 Solarol used in processing

Figure 1.4 A solarized step wedge and the corresponding H and D curve. BroviraSpeed No. 4 paper and 1 + 1 Solarol used in processing.

It is generally considered desirable, in a solarized image, for the region of lowest density to have as low a density as possible. That is, the highlights should be as white as possible, or as light a gray as possible. Stated in graphic terms: the lower the minimum in the curve of Fig. 1.4B (the bottom of the U- shaped curve), the better the solarization.

The minimum in the Sabatier H and D curve is the cause of the white or black edges often seen in solarized photographs. These edges - often mistakenly called Mackie lines* -

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* See Chapter 2, under Mackie Lines and Sabatier Border Lines, for a technical discussion of these two kinds of lines.

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are more pronounced the lower the minimum in the curve. When a solarized negative is used to make a print by conventional processing, the white border lines in the negative cause the formation of black border lines in the print. On the other hand, if a normally- processed negative is used to make a print by solarization, white border lines are produced in the print.

Figure 1.5 A normally-developed negstive of the Golden Gate bridge was used to make this solarized print in which fine white border lines surround many of the structural units. [c/r W. L. Jolly]

Figure 1.6 This print was produced by using the print of Fig. 1.5 as a paper negative, with normal processing. Note that the print has some of the characteristics of a line drawing. [c/r W. L. Jolly]

Some idea of the variety of effects possible in solarization can be seen in Figure 1.7, where processing procedures and images are represented schematically in flow- sheet form.

Figure 1.7 Some processing sequences for preparing black-and-white solarized prints.

Effect of the Film or Paper

The technical quality of a solarized image (as measured, say, by the reciprocal of the minimum density in the H and D curve) is dependent on the photographic material (film or paper) used and, especially in the solarization of paper, on the composition of the developer. If either of these factors is not optimal, the solarized image can be "muddy," with gray highlights. The traditional remedy for muddy solarization has been to use photographic materials of extremely high contrast and to increase the contrast still further by successive copying of the solarized image. For example, a commonly used procedure is to make a positive copy of a solarized negative on a sheet of lithographic film, to use that positive to make a negative copy on a second sheet of lithographic film, and then to make a final print using that negative. Each copying step causes such a large increase in contrast that the final print usually lacks all tones between white and black. The same sort of contrast enhancement can be accomplished by printing through paper positives and negatives. The contrast enhancement can also be moderated by using films or papers of medium or low contrast and by using low- contrast developers.

It should be emphasized that, when solarizing photographic papers, the choice of paper is very important. Many enlarging papers give rather poor results (high minimum densities) no matter what kind of developer is used. However, if a suitable developer is used, good results are obtained with Agfa Brovira and BroviraSpeed papers, a fact that has been frequently noted in the literature.*

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* See references 27, 53, 104, 116, 126, 134, 137, 138, 139, 140, 196, 200, 229, and 238. A technical explanation for the superiority of these papers for solarization is given in Chapter 5 under Emulsions with Mainly Surface Sensitivity Sites.

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Figure 1.8 What appears to be a moonlit scene is a simple print solarization made from a negative of a sunlit scene. BroviraSpeed No. 4 paper was used with 1 + 1 Solarol. [c/r W. L. Jolly]

Figure 1.9 This print was made with the same materials used for making Fig. 1.8, except that Portriga Rapid paper was used. The solarization conditions were optimized for this paper. [c/r W. L. Jolly]

Figure 1.10 This print was made with the same materials used for making Fig. 1.8, except that 1 + 2 Dektol developer was used. The solarization conditions were optimized for this developer. [c/r W. L. Jolly]

A poor solarization can sometimes be remedied by judicious bleaching with a combination of ferricyanide and thiosulfate (Farmer's reducer) to lighten the minimum density regions. However, it is generally much more satisfactory to increase the contrast by making a series of positive and negative copies with high- contrast film or paper, as described above.

Effect of the Developer

Most general- purpose developers contain both metol and hydroquinone as the active developing agents. These developers serve fairly well in the solarization of film, but give muddy results (high minimum densities) in print solarization. The fact that an aged (heavily used) metol- hydroquinone developer gives better print solarizations than the fresh developer has probably been in the lore of solarization for many years. The earliest statement of this fact that I have been able to find in the literature is that by Regas²⁰⁰ in 1972, although the same claim was made in 1973 by Tennen and Levine²²⁹ and soon thereafter by Walker and Rainwater.^196,238

In 1973, Sandy Walker, Clarence Rainwater and I struggled for months to determine what it was about old, brown developer that favors the low minimum in the Sabatier H and D curve. For a while we suspected that the dark brown oxidation product of metol was the causative agent. One day I made up a developer solution containing metol, sulfite, carbonate, and bromide, and bubbled air through it for several hours to oxidize a large part of the metol. I then used the resulting dark brown solution as the developer in a print solarization. The result was astounding. I had never seen such a beautiful solarization, with almost pure whites in the minimum density region! I immediately called up Rainwater to tell him about my results. The next day, he, in turn, called me to report even more interesting results. He had just obtained equally good solarizations using the same sort of developer that I had used, but without the air oxidation step! In other words, a fresh solution of developer, containing only metol as the developing agent, functions as a good solarizing developer. It was then clear to us that the inclusion of both hydroquinone and metol in a developer makes it unsatisfactory for solarization of paper. Heavily used developer solutions give good print solarizations merely because the hydroquinone has been consumed, and the sole active developing agent is the remaining metol. This explanation is consistent with the often- cited mechanism of metol- hydroquinone development, in which the metol molecules act principally as conduits of electrons from the hydroquinone molecules to the developing silver bromide grains.^106,125,159

Our discovery made it possible to obtain high quality solarizations of prints with complete reproducibility. The well- used metol- hydroquinone developers that had been used previously suffered from several disadvantages: (1) They were not easily prepared with reproducible activity. (2) They were dark brown, making it difficult to see the developing print or film, and (more importantly) making it difficult to give the entire surface of the print or film a uniform second exposure. (3) Being almost exhausted, they had a short useful life. On the other hand, a freshly- made metol developer, properly formulated, has a reproducible composition and activity, is practically colorless, and has a long useful life. A print or film immersed in such a clear developer can be uniformly exposed to light in the second exposure and can be clearly observed during the subsequent development.

After considerable trial- and- error experimentation, we came up with the following formula (published¹³⁷ in 1985) for a stock solution of "solarizing developer" having the desirable characteristics outlined above.

Metol 12.0 g
Sodium sulfite, anhydrous 37.6 g
Sodium carbonate monohydrate 41.0 g
Sodium bromide 4.8 g

Dissolve chemicals, in the order given, in about 850 mL of water at room temperature, and then dilute to 1 liter. For solarization of enlarging papers, dilute with an equal volume of water and use at 16- 18^oC.

A proprietary formulation of this general type has been marketed under the trademark Solarol from 1975 to 1987 by the Solarol Co., Inc., and since 1988 by Brandess Bros., Inc. This product has received numerous commendations for its efficacy in solarization.*

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* See references 29, 30, 42, 61, 81, 97, 103, 126, 127, 151, 152, 172, 197, 199, 208, 227 and 240.

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Kodak Selectol- Soft is another hydroquinone- free developer that can be used for print solarizations; the stock solution has about the right concentration for use as a working solution in solarization. Unfortunately, Selectol- Soft solutions have a distinct tendency to turn brown.

For convenience, I shall hereafter use the term "Solarol- type developer" to designate any developer with a composition similar to that given above. Even though the composition of commercial Solarol probably does not correspond to the above formula, the differences in properties are small enough that the developers can be used interchangeably.

It will often be found that Solarol or Solarol- type developer solutions (either stock or diluted) that have been stored for a long time have insoluble particles in suspension. Satisfactory results can often be obtained by allowing these particles to settle out and by decanting the solution from the particles. However, a better procedure is to filter the solution through a small plug of cotton wool or a sheet of facial tissue in a glass or plastic funnel. In common with most dilute developer solutions, diluted Solarol is oxidized badly when allowed to stand for a day or two in an open tray. It is economical practice, after brief darkroom sessions, to pour the used developer solution into a bottle which can be sealed airtight. Carbonated- beverage bottles with plastic- lined screw- caps are very useful for such storage. To avoid oxidation by air, it is best to fill the bottle almost full or to displace the air over the solution with an inert gas, such as that provided by a can of Dust- Off, before sealing the bottle.

In 1990, Rees¹⁹⁹ published a formula for a metol- only developer for print solarization. This developer contained, per liter of working solution, 4.5 g of metol, 5.0 g of sodium sulfite, 12.5 g of sodium carbonate, and 0.75 g of potassium bromide. Unfortunately, he showed no examples of prints solarized with this developer; indeed he indicated preference for a similarly constituted developer, containing benzotriazole, and a procedure involving paper presoaked in developer and two successive enlarger exposures. (See Chapter 4, under POP Solarization.)

Because the minimum densities in solarizations are not as low when metol- hydroquinone developers are used as when metol- only developers are used, special care must be taken when resin- coated papers are solarized. It is a fact not widely known that the emulsions of most of these papers are pre- impregnated with hydroquinone so that they can be used in automatic machine processors. Although good results can be obtained by solarizing these papers in the usual way with a metol- only developer, after developing several sheets, the developer becomes significantly contaminated with hydroquinone. Therefore it is good policy to wash resin- coated papers in plain water for at least one- half minute before putting them in the developer.

Recommended Procedures for Paper and Sheet Film

First Exposure. -

Whether one solarizes paper or film, the initial exposure is very important, inasmuch as it determines the overall nature of the final image. If the initial exposure is fairly heavy, the final image will be like the image obtained by normal development, no matter how heavy the second exposure. If the initial exposure is light, the final image will show reversal - that is, tonal values paralleling those of the initial exposure. An intermediate initial exposure can yield a final image containing both negative and positive regions, and it is this type of image that has fascinated the artistic practitioners of solarization. In Chapter 4, I shall discuss the relationship between the magnitude of the initial exposure and the appearance of the final image, in a wide variety of applications.

When high- contrast emulsions, characteristic of most papers and lithographic films, are solarized, slight changes in the initial exposure cause relatively big changes in the developed density. Hence, if high reproducibility is sought, the initial exposure must be controlled carefully. In the case of papers or films which receive the first exposure under the enlarger, exposure can be precisely controlled by maintaining the light intensity constant with a voltage stabilizer in the enlarger circuit and by setting the exposure time with a good timer- switch. In the case of high- contrast films which receive the first exposure in the camera, a difference of one- half stop can make a big difference. Therefore it is advantageous to use a camera which has fine control of the f- stops or the exposure time.

The optimum magnitude of the first exposure must be determined by trial and error and depends on the type of solarized image desired - that is, on the relative amounts of positive and negative images desired. As a rough rule, if approximately equal amounts of positive and negative images are desired, the first exposure should be about one- half of that required to give a normal- looking, unsolarized, print or negative.

First Development. -

A Solarol- type developer, diluted 1 + 1, is usually the best developer for paper. In the case of films, the optimum developer and its concentration is a function of the effect desired.*

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* See Chapter 4 for recommended processing conditions for various films.

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Development is carried out in a black tray. Because the second exposure comes soon after the start of the development, it is particularly important that the sheet be developed evenly. Therefore, the sheet is quickly slipped into the developer, agitated vigorously for 20 or 30 seconds, and then agitated more gently at regular intervals.

The first development time (chosen to produce the lowest possible minimum density consistent with a reasonable maximum density) ranges from about 35 seconds for RC papers to about 5 minutes for some high- speed films. For a fiber- base paper such as Agfa Brovira, the best time is about 55 seconds.

Second Exposure. -

Some researchers, using metol- hydroquinone developers, have recommended that, immediately after the first development, the print or film be removed from the tray, squeegeed on a flat surface, and then given the second exposure. However this awkward procedure is completely unnecessary, indeed undesirable, if a Solarol- type developer is used. Ideally, the sheet should remain under the developer solution from the beginning of the first development until the end of the second development. Because the second exposure time is usually short compared to either the first or second development time, it makes little difference whether the second exposure time is considered to be part of the first or second development time. In my work, I have, rather arbitrarily, always treated it as part of the second development time. Thus the start of the second exposure effectively marks the end of the first development.

During the second exposure, it is important that the developer solution covering the sheet of paper or film be calm, with no ripples or floating bubbles. Such surface imperfections can cause nonuniform illumination of the print and a mottled appearance in the second development zones. Therefore agitation should be ceased during the last few seconds of the first development. For the same reason, any debris floating in or on the developer solution should have been previously removed.

An electrical socket with an incandescent light bulb, 40 to 100 watts, should be positioned about three or four feet above the developing tray and should be provided with a convenient switch. Because the switch is likely to be touched with damp hands, all exposed metal parts must be electrically grounded. The intensity of the second exposure can be varied by changing the height of the light bulb over the developer solution, by changing the wattage of the light bulb, or best, by using an electric light dimmer. To achieve complete reproducibility in the second exposure light intensity, a 0- 120V AC voltmeter can be connected across the light bulb. With a light dimmer to control the voltage and a voltmeter to measure the voltage, it is possible to apply essentially any desired voltage to the bulb, and thus to provide almost any desired light intensity. If the bulb and its height are not changed, the light intensity can be exactly reproduced from one printing session to another by reproducing the voltage. Even without a voltmeter, the dimmer switch greatly facilitates making small changes in light intensity.

The light that falls on the developing tray during the second exposure should be evenly distributed over the tray. Usually the lighting will be even enough if the light bulb is no closer than about three feet and if there are no highly reflective surfaces nearby. It is good to use a bulb that is completely frosted, with no imprinted design on the side facing the tray; otherwise the light will not fall uniformly on the tray. It is even better if the bulb is enclosed in a light- box with a window of opal glass or translucent plastic; then the tray can be illuminated with essentially perfect uniformity.

A jet black tray should be used to avoid reflection from the sides of the tray onto the paper or film. If relections from the sides of the tray cause trouble, a tray much bigger than the sheet of paper or film should be used, so that the sheet can be placed in the middle, well away from the sides.

For papers, the second exposure time should ordinarily be between three and ten seconds. Longer exposure times are not recommended because (1) with long second exposure times the density developed in the very low initial exposure regions during the second development is almost independent of the exposure time (i.e., the density does not increase much with increasing time); and (2) long second exposure times can cause an increase in the minimum density (corresponding to "muddy" Sabatier border lines). Exposure times shorter than three seconds cannot be reproduced accurately enough without use of an electronic timer. Of course, with an electronic timer, times as short as one- tenth of a second can be used. However, such short times have little quantitative significance for calculating relative exposures because they are shorter than the warm- up time of the light- bulb filament.

Films are generally much more light- sensitive than papers, so the corresponding second exposure times are shorter (typically, around one second), even when relatively weak light sources are used. Hence an electronic timer is almost essential when solarizing film.

Second Development. -

For convenience we assume that the second development starts at the same time that the first development ends, and ignore the short time required for the second exposure. To obtain development of the full range of tonal values, the second development must not be cut short. In the case of Agfa Brovira paper, for example, the second development should last for about one minute. Photographers who are accustomed to solarizing prints with a relatively fresh metol- hydroquinone developer such as Dektol (and are accustomed to the consequent rapid, strong fogging of the print) must resist the temptation to snatch the print from the developer too soon. All the remaining processing steps (stop- bath, fixer, washing, etc.) are the same as in ordinary, non- Sabatier processing.

Getting Acquainted with the Technique. -

Do not be daunted by all the details and warnings in the preceding discussion. The Sabatier process is not difficult. Beautiful, exciting solarizations can be obtained without any special equipment and without any previous experience. If you wish to go through the motions of solarization and obtain an interesting print with both positive and negative character, first mount a negative in an enlarger and determine the exposure that you must give a sheet of Agfa Brovira paper (glossy, grade 4 or 5) so that normal development in 1 + 1 Solarol gives a pleasing image, with a good distribution of tones, from white through black. Then, for the solarization, give an enlarger exposure about two- thirds or three- quarters as long. Develop the print in the same developer for about 55 seconds, turn on an overhead light for five seconds, and continue developing for a further minute. If the second- developed image comes out too dark, reduce the light intensity; if it comes out too light, increase the light intensity.

Roll- Film Solarization

The Sabatier development of 35- mm. film is more difficult. Tank development, with the film in the usual metal or plastic reel, is not recommended because under these conditions the film cannot be given a uniform, diffuse second exposure. Tray development is difficult because of the tendency for the film to curl, even when wet.⁷⁸ One way of solving this problem is to cut off a 10- inch length of the film and to clip this strip, emulsion side up, on a dense, black plastic lath that is laid in the bottom of a tray of developer. Processing is then carried out much as in sheet film processing. Another way of solarizing 35- mm. film is to use a long vertical glass tube (say, 41 mm. i.d.; 45 mm. o.d.), sealed off at the bottom end, as a developing tank. Such a tube can be used to develop an entire 24- exposure strip of film. Metal clips are attached to the ends of the film strip, the upper serving as a handle, and the lower serving as a weight to keep the film strip straight. The strip is lowered into the tube of developer and jiggled every five seconds or so. The second exposure is made with a light bulb about 4 ft. from the tube in the direction toward which the film emulsion faces. At the end of the second development period, the strip is lifted out of the tube and is immediately immersed in a deep tray of stop bath. The film is then wound onto a plastic developing tank reel, and fixing and washing are carried out as in conventional tank processing.

A convenient way to solarize roll film wider than 35 mm. might be to clip a strip of the film, emulsion side up, onto a flat plate which is then laid in a tray of developer and processed as if it were a sheet of film.

Go to Chapter 2

Last Modified: 8/14/97