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Reilly, James M. The Albumen & Salted Paper Book: The history and practice of photographic printing, 1840-1895. Light Impressions Corporation. Rochester, 1980.


Chapter Seven
Tone Reproduction and Print Exposure

Now if we had complete control over the finished negative as to be able always to predetermine its character, we should unhesitatingly produce all negatives so that they would stand printing in sunshine for all or the principal part of the exposure to light. Somehow it appears that those prints are most admired which have had actual sunshine direct on the negative during all, or nearly all, the process.

--Thomas Bolas, 18891

Those who have had experience in ordinary photographic processes know how important the developing step is in determining the density, contrast and even the color of the photographic image. In all printing-out papers--including albumen and salted papers--the "development" step is equally important in determining the color, density and contrast of the image; only instead of varying with the composition of the developer or the time, temperature, etc., the image is affected by the color and intensity of the exposing light and the duration of exposure. In printing-out papers, exposure and development are simultaneous and inseparable. The exposure step is in many ways the most exciting aspect of printing with albumen and salted papers. It is quite a thrill to place a sheet of hand-coated paper in the printing frame for the first time and watch it darken, and it is a refreshing change to bring photographic processes out of the darkroom and into the sunshine. This chapter examines the relationship between negative characteristics and tone reproduction in albumen and salted papers as well as the theory and practice of print exposure.

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Fig. 32. Printing frames in use.

Characteristics Required in Negatives for Albumen and Salted Paper Printing

Each photographic paper has a fixed set of tone reproduction characteristics; among these are the maximum density attainable on that paper, the number of tone steps of a graduated gray scale that it can reproduce (this is referred to as scale length or gradation) and the contrast of the paper, which refers to how rapidly or slowly the transitions from light to dark occur. In order to produce a negative with the proper contrast and density range to make the best possible print on albumen and salted papers, the tone reproduction characteristics of these papers will have to be taken into consideration.

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Fig. 33. A special printing frame for "combination" printing, i.e., using several negatives in succession to make one print.

Unlike develop-out papers, where graded or variable-contrast materials offer a way to match the paper to the negative, consistently good results can only be obtained on albumen and salted papers by closely matching the negative to the requirements of the paper. Although there do exist some ways to affect print contrast with printing-out papers, these certainly do not provide as flexible a response to the negative as modern develop-out papers can. Also, many of the contrast-control techniques that are available for printing-out papers can only be used at the expense of optimum print quality.

Much experience has shown that even the densest and most contrasty negatives that will still print satisfactorily on develop-out papers do not possess sufficient density and contrast to make good prints on albumen and salted papers. To achieve the finest quality prints on either kind of paper--develop-out or printing-out--will mean exposing and processing negatives for that kind of paper alone, because "compromise" negatives will print well on neither kind. Even between albumen and the various kinds of salted papers significant differences in negative density range and contrast are called for. As a general rule, however, all printing-out papers require negatives with a greater density range--which implies higher maximum densities--than develop-out papers do.

EFFECT OF BINDER MATERIALS ON TONE REPRODUCTION

Guidance in producing suitable negatives for albumen and salted paper printing first comes from the nature of the binder material of the specific paper chosen. If the paper is glossy, as in the case of albumen paper, then a negative of shorter density range is required than would be necessary for a matte surfaced paper. In considering density range of a negative, it is the difference in density between the lowest and highest densities that needs to be determined, not just the highest density. A negative may be very dense indeed and still be "flat," with only a small relative difference between the minimum and maximum densities. The reason why glossy papers call for a negative with a lower density range is that glossy papers have a transparent binder (for example, albumen) which minimizes diffuse reflections and scattering of light by the paper fibers. This effectively produces more "brilliance" and contrast in the image by making the whites appear whiter and the shadow areas denser. The same amount of reduced silver which produces a deep shadow on glossy paper will produce a much paler looking shadow area on a matte surfaced print. To overcome this difficulty and produce a dense "black" on matte papers requires relatively more reduced silver, and that translates directly into longer exposure times. To permit longer exposure times a negative must have sufficient density in the highlights to keep the lighter tones in the print from becoming too dark. Hence a longer density range negative is called for with matte papers than with glossy papers. Following this rule, plain salted papers will require the greatest density range in a negative; matte papers like arrowroot and matte albumen, slightly less; and albumen paper still lower. Of course, the negative density range for albumen paper will still be considerably higher than that called for by develop-out papers.

USING A GRAY SCALE TO MEASURE GRADATION AND CONTRAST

From the above explanation it will be clear that since there is a great deal of variation in the nature and amount of binder materials used on albumen and salted papers, no exact density ranges can be specified for all negatives intended for these different papers. However, there is a handy way to determine the necessary density range once a given paper has been fabricated. A sample sheet of paper is sensitized, printed from a 21-step gray scale and processed in the normal way for that paper. The exposure of the test sheet must be long enough so that the maximum possible density has been attained. This can be verified by making sure that the area of the print under the first step of the gray scale has reached the same density as the margins of the print which protrude beyond the gray scale itself. The number of steps of the gray scale which can be counted in the finished print is the "scale length" of that particular paper. Each photographic paper has its own characteristic number of steps produced in such a test. The appropriate negative density range for printing on that paper is approximately the same as the difference in density between the highest and lowest discernible steps on the gray scale. In practice, detail is always lost at the highest and lowest extremes of density in the print, so negatives with slightly shorter density ranges than those indicated by the test are usually employed. As would be expected, plain salted papers have the longest scale length in a test like this, matte papers have a slightly shorter one, and albumen paper the shortest.

Hübl found that in the tests he performed the scale length of glossy albumen paper was equal to that of platinum paper, and that the scale length of salted papers exceeded that of platinum paper by a considerable margin.2 The long scale length of albumen and salted papers means that more of the detail present in negatives can be reproduced in the print than would be possible with shorter-scale materials, such as currently available develop-out papers. One of the reasons why all printing-out papers tend to have long scale lengths is because of the so-called "self-masking" property. This describes the phenomenon by which the density built up in shadow areas of the print during exposure acts as if it were a "mask" on the lowest density areas of the negative. As the silver builds up in the shadow areas of the print, it behaves as if it were additional density in the negative; this delays the attainment of maximum density in the print and tends to prevent the loss of all shadow detail before the highlight detail has time to "print in." The net effect of this "self-masking" action is to yield prints with good shadow density and detail while retaining a delicate gradation of lighter tones. With printing-out papers generally there is far less tendency to produce harsh "soot and chalk" prints than with developing-out papers.

Another important characteristic of every photographic paper that bears on the type of negative required for best results is its inherent contrast. As explained above, this refers to the progression of tones between the darkest and lightest, and whether this progression is smooth or abrupt. Two papers with the same scale length may not have the same contrast. For example, Hübl found in his investigations that although albumen and platinum paper possessed the same total scale length, when they were compared with the contrast of salted paper as reference, albumen paper had a slow progression of tones from the shadows to the middletones and a relatively abrupt jump from the middletones to white. With platinum paper the opposite takes place--the transitions from the highlights to the middletones are relatively soft while there is an abrupt jump down to the deep shadows.3 These facts were ascertained by comparing the densities of each step of the gray scales on the three papers. The conclusions to be drawn from this are that although the density range of an optimum negative for albumen and platinum paper is the same, a negative intended for albumen printing should emphasize highlight detail at the expense of shadow detail, in order to compensate for relatively high contrast in the highlight end of the scale on albumen paper.

In performing similar tests, modern albumen and salted paper printers can measure print densities on a reflection densitometer and plot them graphically against the densities of the steps of the gray scale in order to get an accurate measurement of the gradation and contrast of the particular paper they are working with. Negative contrast can then be adjusted accordingly; however, the exposure and processing conditions for the test must be the same as those used in normal practice, or the test results will be misleading.

Print Exposure

While print exposure may appear at first glance to be one of the more simple and straightforward aspects of albumen and salted paper printing, in reality it is one of the most complex. The biggest difficulty arises from the fact that the color and intensity of the exposing light affect the color and ultimate contrast of the print. Albumen and salted paper prints are primarily sensitive to ultraviolet radiation, and only to a much lesser extent to visible blue light. In choosing a light source to expose albumen and salted paper prints the main consideration is not how bright the light appears, but how much UV radiation it emits. The most convenient source of UV radiation is of course, the sun. Historically, no artificial light sources were available until the advent of the electric arc lamp in the 1880's, but the arc lamp was so impractical it was almost never used in the 19th century for printing purposes--it was dangerous and intimidating enough as a studio lighting device. The most satisfactory modern artificial light source is the metal halide lamp, developed in the 1960's and now used extensively in the graphic arts industry to expose lithographic plates and stencils for screen printing. Metal halide lamps exceed the sun in their UV output and do not have the drawback of releasing noxious fumes as did the carbon arc lamps that were previously used for those purposes. The disadvantage of metal halide lamps is their expense--a complete installation consists of a costly lamp tube, a lamp housing with a mechanical shutter and a separate power supply. Other, less expensive artificial light sources such as sunlamps, quartz halogen lamps, black-lite fluorescent tubes, or photofloods, are inadequate to the task.

For those without access to metal halide ramps the next best alternative is the sun.

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Fig. 34. An indoor printing studio, ca. 1890. A south-facing orientation was best for printing.

For all its problems and undependability, the use of sunlight (or more properly, daylight) has accounted for all but a tiny fraction of the albumen and salted paper prints ever made. The trouble with sunlight is that it is constantly changing in its UV output. The intensity of UV radiation in daylight waxes and wanes in annual and daily cycles, reaching a peak in the month of June in the annual cycle and at the hour of noon in the daily cycle. There is also the problem of an infinitely varying cloud cover. Still another difficulty associated with the use of daylight is the fact that the sensitivity of albumen and salted papers is considerably lowered when the temperature dips below 5 C, so printing outside in winter is practically impossible.

EFFECT OF THE LIGHT SOURCE ON PRINT CONTRAST

A very intense light source lowers contrast in the print, while a weaker light tends to heighten print contrast slightly. Thus the old rule, found in many 19th-century manuals, which advises that dense, vigorous negatives be printed in sunlight and thin, weak negatives be printed in the shade. "Printed in shade" means facing open sky but not directly in sunlight. Also recommended in many old manuals is the technique of covering the printing frames with tissue paper or ground glass and printing in direct or filtered sunlight. Whether the majority of printing will be done in the shade or in sunlight depends on the character of the negatives to be printed. If the printer is using negatives of his or her own that were intended exclusively for albumen and salted paper printing--and providing the locale offers a fair amount of annual sunshine--then a good plan is to try and make the negatives so that they will stand up to full sunshine. Not only will the prints be more permanent, they will have a more pleasing tone and look richer and more brilliant.

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Fig. 35. A rack for holding printing frames outdoors. Such portable racks were part of every small studio's equipment.

The color of the exposing light also has an effect on print contrast. The higher the proportion of blue light and the lower the proportion of yellow light the exposure source contains, the greater will be the tendency toward a softer, flatter print. The greater the proportion of yellow and the less blue the exposing source contains, the greater will be the tendency toward a more contrasty print, but, of course, with an accompanying lengthening of exposure time.4

EXPOSURE TIME

The "speed" of albumen and salted papers is exceedingly slow. Matte salted papers like arrowroot paper are the fastest, followed by plain salted papers and the slowest of the lot is albumen paper. An average exposure time of albumen paper in direct sunlight is 5 to 10 minutes, in shade, anywhere from ½ hour to several days. Of prime importance is the careful monitoring of exposure so that the correct amount of exposure is given the print; the necessary exposure required by a given negative will vary greatly with conditions. The exposure of albumen and salted paper prints must be carried on past the point where the print "looks right," since the prints lose density in the toning and fixing solutions. The degree of overprinting necessary depends on the nature of the binder material, the character of the negative and the type of toning bath used. Experience is the only way to know precisely how much overprinting is required, but a starting point for beginners might be to overprint one and a half "stops" for albumen paper and two "stops" for salted papers.

A good approach in determining the progress of exposure is to watch the margins of prints as they are exposing and make an initial check a short time after the margins appear to have reached maximum density. This advice would not apply in the case where a very thin negative is being printed because by the time the margins have attained maximum density, a print from a very thin negative will have most likely been spoiled. A guide to the point when maximum density has been attained is when the margins of the print begin to "bronze," that is, take on a greenish luster. At this point so much metallic silver has been reduced in the light-sensitive layer that a kind of saturation point is reached and particles of silver migrate to the surface of the layer and form a coherent, shiny film. If the "bronzing" has not progressed too far it may disappear during processing; otherwise, it will still be noticeable in the finished print, though not as prominently as before processing. Many old manuals on albumen printing recommend printing until the shadows are "just bronzed," and this is correct advice for many negatives, especially ones which can be printed in full sunshine.

Some Precautions in Printing

Neither the paper nor the printing frames should be excessively dry at the time of printing, because a certain amount of moisture is necessary in order to assure good sensitivity and contrast, especially with matte salted papers. The paper should contain enough moisture to be flexible and not feel dry and brittle. Conditioning the paper in a moist environment may be necessary. However, under no circumstances should the paper be damp or actually wet, because if some of the silver nitrate from the paper becomes transferred to the emulsion of the negative, red stains will result. Precautions against this accident should be taken whenever a valuable negative is to be printed. One mil (.001 inch) MylarTM can be placed between the negative and the paper without sacrificing sharpness.

If a relatively cold printing frame is placed out in sunlight the expansion of the paper and the negative with heat may be unequal, and the result is a "doubled" image all around the outside edges of the image area while the center of the print remains sharp and crisp. This phenomenon is more likely to occur with large negatives and prints. Likewise, in bringing the frames inside to check the progress of exposure, care should be taken to avoid leaving half the frame lying open for more than the minimum time necessary to check exposure. Never open the frame to check exposure in sunlight or open shade; bring it inside to a safe location, preferably a room lit by a white incandescent light of low wattage. In this light the prints can be judged with reasonable leisure and safety.

A Note on Printing Historical Negatives

One of the pleasures of albumen and salted paper printing is to be able to print historical negatives on the kinds of positive printing materials for which many of these negatives were originally intended. A comparison between an albumen print made from a 19th-century negative and the "best possible" approximation of an albumen print made from the same negative on modern papers will quickly establish the superiority of the "real thing."

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Fig. 36. A "Scovill" brand printing frame. Usually made of maple, such frames were cheap and durable.

In printing from historical negatives the first and most important rule is to protect the negative; use the 1 mil MylarTM spacer between the negative and the printing paper. Learn to handle glass negatives before attempting to print from a really valuable negative, because many negatives have been shattered in printing frames from too much pressure, or cracked by expansion in sunlight from an overstressed frame. Use a frame that was intended for glass plates, and use a pad.

There is always some risk inherent in printing from a valuable negative, so the risk will have to be carefully weighed against the benefits of a facsimile print. For extremely valuable negatives a duplicate negative can be made at somewhat less risk to the original negative and prints then made from the duplicate negative. Whenever possible, this is the procedure that should be employed. Undoubtedly the making of new albumen prints from historical negatives will find a place in future photographic practice, because ,the appreciation of historical images is greatly enhanced by the use of the appropriate positive printing material. Any and all facsimile prints, however, should always be indelibly marked as such, with an embossed stamp or other method of identification.


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