Ten photographs from the Thomas Walther Collection, showing the variety of techniques, papers, formats, and presentation styles represented. The prints are arranged in groupings of glossy, semireflective, and matte paper surfaces, from left to right. Department of Conservation, MoMA


This glossary is designed to guide the reader through the materials and techniques used in the creation of the prints in the Thomas Walther Collection. In the period between the two world wars, photography was characterized by boundless creative expression. Stimulated by revolutions in technology—the development of new smaller and more portable cameras, motion-picture and low-light cameras, enlargers for making positive prints from negatives, and easy-to-use photographic papers—artists and other serious amateurs began to explore the medium, freely experimenting in the darkroom and in the studio, producing negative prints, collages and photomontages, photograms, solarizations, and combinations of these. The industry responded to the expanding range of users and equipment with new photographic papers in an assortment of textures, colors, and sizes. Made by practitioners ranging from amateurs to professional portraitists, journalists, illustrators, designers, critics, and artists of all stripes, these prints—and the materials and techniques they embody—represent the kaleidoscopic multiplicity of photography in this period of diversification.


  • back printing

    Back printing describes a word mark or logo printed on the verso of a photographic paper during the manufacturing process. Such brand marking appears to have commenced around 1923, when Eastman Kodak printed “Velox” on the verso of its wildly popular gaslight paper of that name. Prior to this date, back printing was used for postal markings on photographic postcard papers, with manufacturer’s logos printed where the stamp would be placed. To ensure that the marks remain invisible on the recto, back printing is very faint. It usually appears in a repeating pattern, sometimes aligned at an angle to the edge of the paper.

  • baryta, baryta-less paper

    The baryta layer is an opaque reflective layer of barium sulfate (also known as blanc fixe) or other opaque white pigment suspended in a gelatin binder, applied to a paper base, and subsequently coated with a light-sensitive emulsion. Thicker baryta layers give the print a flat, uniform surface, and thin layers retain the texture of the paper. Both printing-out and developing-out papers were manufactured with baryta layers starting in the 1880s.

    Baryta-less papers were produced for commercial and industrial uses, such as the photographic copying of office documents and engineering plans and drawings (without the brittle barium sulfate, these documents could be folded and mailed without cracking emulsion compromising any design elements), but photographers discovered that its translucent quality was ideally suited to paper negatives. Around 1925, baryta-less paper emerged as a category of specialized gelatin silver photographic paper that mimicked platinum prints and other artistic papers. It was available in a range of soft, slightly textured surfaces and tonalities and was favored by photographers seeking alternatives to the glossy surface of gelatin silver prints.

  • coating

    Coated prints have a liquid or malleable compound applied to the surface. Various coatings protect the work from the environment, saturate the image to improve its quality, change the paper’s reflective properties from matte to glossy or from glossy to matte, and act as a receptive substrate for retouching materials. Photographers have used numerous homemade and proprietary products, either individually or in mixtures, including waxes, natural or synthetic resins and polymers, and oils in aqueous or solvent bases; these can be brushed, sprayed, poured, wiped, or dabbed on. Skillfully applied coatings are often invisible to the naked eye.

  • collage, photomontage

    In a collage, an artist creates juxtapositions from torn, cut, or folded fragments of an assortment of materials by assembling and then securely positioning them on a common support. In some cases the artists take pains to make the composition as seamless as possible, and in others they let the edges become part of the effect; some collages include additional drawing or painting on the surface in pencil, pen, or brush. In a photomontage the collage is photographed and printed to produce a new image. To create the illusion of seamless integration, artists make photomontages in two or more generations, photographing the new image after each alteration. Handwork in pencil, pen, or brush can be added at any stage.

  • contact print

    When light-sensitized paper is placed in direct contact with a negative and then exposed, the result is a contact print. A printing frame tightly binds the materials together during exposure, to ensure perfect registration and the best resolution.

  • copy print

    If an original negative is fragile, too large, too small, or unavailable, a new negative can be created by photographing an existing print, making a negative that then becomes the source for second-generation photographs. Copy prints can be made carefully enough that they resemble first-generation photographs. Second-generation photographs also form essential steps in the making of photomontages.

  • developing-out paper

    The most commonly used photographic paper of the twentieth century was developing-out paper, which contains silver bromide emulsions that react quickly when exposed to light, even at very low intensities and brief exposures. Unlike the slower silver chloride printing-out papers and silver chlorobromide “gaslight papers,” this paper requires the controlled environment of a darkroom for handling and printing, and it is well suited to the dim levels of light produced by an enlarger (natural light is a great deal brighter). There are numerous variations on the chemical composition of image materials in developing-out papers, but all of them require chemical development to bring out the image in the print.

  • double exposure

    In a double exposure, or multiple exposure, the artist creates a composite image either in the camera or during the printing process. For the in-camera version, one exposure is made after another without changing the film or plate or advancing the filmstrip. In the darkroom this effect can be created by stacking negatives in the negative holder or by exposing a paper multiple times to one or more negatives. Portions of the photographic paper can also be masked and exposed in sections. These procedures capitalize on photography’s inherent transparency: layered images can appear as discrete see-through shadows while still retaining a considerable amount of detail.

  • enlargement

    To make a photographic print that has larger dimensions than the negative, a strong light is projected through the negative, via the specialized lenses of an enlarger, onto light-sensitive paper. The size of the print is determined by the distance between the negative and the paper: the greater the distance, the larger the image appears. Some artists also make prints by first enlarging the negative (via an interpositive, made by exposing another piece of film to the negative) and then contact printing from it. By the late 1920s, following the rise in popularity of silver bromide paper, which was produced to meet the demand for larger prints, enlarging apparatuses were standard darkroom equipment.

  • enlargement via lateral projection

    The earliest enlargers focused light horizontally through a condenser lens with glass plates or film negatives secured to it; in this process, the lens acts like a spotlight, projecting the image onto a sheet of unexposed photographic paper usually pinned to an easel. In many cases the only traces of this method are tiny white lines where the shadow cast by the pins blocked the exposure. This system of enlarging requires no specialized equipment: medium- and large-format cameras can be converted into lateral enlargers with minor modifications. Lateral projection remains the most practical method of making photographic murals.

  • ferrotyping

    A wet, swollen gelatin emulsion will take on the character of any surface pressed into it. To create a high-gloss effect, prints are pressed against a perfectly smooth surface, such as glass or a metal plate, and allowed to dry there. A ferrotyped surface enhances the details of an image, and thus it was standard procedure for photographs intended for reproduction. Imperfect or textured surfaces will yield different effects. Various additives in the postprocessing sequence help separate the print from the plate; heating the plate has a similar effect and also speeds up drying.

  • film frame

    A motion-picture filmstrip captures twenty-four images per second, creating a series of images that when shown by a projector produces the effect of continuous action. Single frames of the filmstrip, or sections of them, can be isolated and printed as photographs. (This is not the same thing as a film still, or production still, which is taken with a still camera for the purposes of promotion and advertising.)

  • gaslight paper

    "Gaslight paper" is a vernacular nickname for a group of easy-to-use developing-out papers that have been credited with bringing photography to the masses. The paper, coated with silver chloride and silver chlorobromide emulsions, which are less sensitive than the pure silver bromide formulation of regular developing-out papers, was especially formulated for printing in weak artificial light, such as that of a gas lamp or electric bulb. Because of their slow development, gaslight papers offer considerable latitude in how they can be exposed and processed and do not necessarily require a darkroom. They are ideally suited to contact printing, which is how they were most frequently employed, although they can also be used with enlargers.

  • lamination

    A print is laminated by fusing cellophane to its surface. The laminate improves the print’s durability and protects it from solvents and moisture. Tinted cellophane adds a colorized effect and may also be employed as a decorative element. Cellophane, a transparent film of regenerated cellulose, became popular in 1930, shortly after it was first developed.

  • mount

    Mounted photographs are adhered to a secondary support of paper, card stock, or thick board. The mount can be larger than the print or trimmed flush to its edges, and multiple mounts may support a single photograph. The mount adds rigidity to the print to protect it during handling or prepare it for display, and it can be part of the format of a portfolio or album. Artists often sign the work on the mount, either on the print’s verso or one of the margins on the recto.

  • negative print

    A negative print looks like the negative it is made from, with the same reversal of light and dark tones. It is made by exposing a second, intermediate material—either film, glass, or paper negative—to create an intermediate step, also known as an interpositive. When paper is exposed to light through the interpositive, the result is a negative print.

  • overlay

    A photograph being prepared for photomechanical reproduction in a magazine or advertisement would almost always have some additions made to it, such as graphic or typographical elements, drawn or printed images, airbrushing, or a combination of the three. To protect the photograph during these additions, a sheet of transparent material such as acetate would be attached on top before they were carried out (and could be removed afterward). The overlay was a more receptive substrate then the slightly water-repellent emulsion.

  • palladium print

    Palladium prints are made with a process that is closely related to that of platinum prints. The paper is sensitized with a solution of iron oxalate and a palladium salt and, once exposed, developed in sodium citrate, cleared (a chemical process that allows the unexposed sensitizer to be soluble in water), and washed to remove residual chemicals, leaving a final image consisting of fine metallic palladium. Palladium prints are prized for their rich, warm tonal scale, their durability, and their resistance to fading. Palladiotype, a palladium paper produced by the Platinotype Company, was introduced during World War I as a less-expensive alternative to platinum paper, which was in short supply.

  • photogram

    When objects are placed directly on an unexposed sheet of photographic paper that is then exposed to light, the result is a photogram. Photograms can be made on any light-sensitive surface and with any photographic process, including daguerreotype plates, printing-out paper, gelatin silver paper, and nonsilver processes such as cyanotype or diazotype. The paper is developed and fixed in the normal way. Photograms were the earliest form of photography and remain the simplest.

  • photographic postcard

    Photographic postcard paper has the same measurements and postal markings as a standard postcard, with the paper company’s trademark stamped on the back and light-sensitive emulsion on the front. Consumers print their own images, as they would on regular photographic paper, using either developing-out or printing-out processes. Postcard stock was widely available by the early twentieth century and was so popular that most of the major paper manufacturers produced their own brands. Some companies even produced postcard-format negatives.

  • photomontage

    See collage

  • pigment print

    Pigment prints are made using a family of imaging systems based on the light sensitivity of bichromate compounds combined with inert pigments in any color. When bichromates are added to transparent organic colloids such as gelatin, albumin, or gum arabic, they cause the colloid to harden and become insoluble in the areas where it is exposed to light, as the unexposed portions of both colloid and pigment are washed away. In each process—carbon print, bromoil print, gum bichromate print, direct carbon print, and others—this change can be manipulated to achieve various artistic effects, such as by using a brush on the wet pigmented colloid to impart painterly brush strokes or a pictorial effect that resembles drawing. The final pigment image of the finished print is more durable than those produced by any other photographic process.

  • platinum print

    Platinum prints are created using a process based on the light sensitivity of a combination of iron oxalate and a platinum salt. After the sensitized paper is exposed, the print is developed in potassium oxalate and then cleared (a chemical process that allows the unexposed sensitizer to be soluble in water) and washed to remove residual chemicals, leaving a final image consisting of finely divided metallic platinum. Platinum prints are prized for their rich tonal scale and durability. Platinotype was the original platinum paper invented and marketed by William Willis, Jr., and his Platinotype Company of London.

  • printing-out paper

    Printing-out paper requires strong levels of actinic light, which is abundant in sunlight, to bring out a visible image, rather than the chemicals required by developing-out paper. It is usually associated with nineteenth-century photography, when contact printing was the principal method of producing a print. The printing-out technique is required for the low sensitivity of silver chloride in gelatin or collodion emulsions, and for processes based on the light sensitivity of iron salts, such as platinum, palladium, and cyanotype processes, as well as bichromates. Because the artificial light from enlargers is too weak for this process, photographers continued to use printing-out papers almost exclusively for contact printing in sunlight, into the twentieth century; enlargements on printing-out paper were made by contact printing from an enlarged negative. Artists with limited means or photographic expertise relied on economical and ubiquitous gelatin silver printing-out paper.

  • retouching (additive)

    In additive retouching, marks are made to the surface of a print in order to correct flaws in the image or enhance compositional elements. The marks can be made with brush or graphite; they often take the form of dabs, spots, lines, or patches of different colors that approximate the image material and, ideally, blend in.

  • retouching (reductive)

    In reductive retouching, portions of the print’s emulsion are changed or removed to eliminate undesired image material, to diminish flaws, such as specks of dust, or to strengthen the composition. These modifications are made by cutting or scraping with sharp implements, often under magnification, in techniques that include etching, scraping, impressing, scratching, and abrading.

  • retouching in negative

    Retouching done directly on the negative can correct spotting and scratches as well as modify the image. These alterations are sometimes visible on the photographic print. Occasionally, retouching done to a print that has subsequently been rephotographed will also be visible on the second-generation print.

  • silver-platinum print

    Silver-platinum prints are made using a process that combines the light sensitivity of iron and silver salts on a paper base. The exposed paper is developed in potassium oxalate and then neutralized, fixed, and washed to remove the residual light-sensitive chemicals. The final image consists of fine metallic silver and platinum. Satista, the Platinotype Company’s silver-platinum paper, incorporated two sensitizers: silver chloride and a combination of iron oxalate and a platinum salt. It was introduced during World War I as an alternative to platinum paper, which was increasingly difficult to obtain, and produced prints that were similar in appearance but more affordable.

  • solarization

    Solarization creates a hybrid image—part negative, part positive—by interrupting the development process to expose the image to an additional flash of light. The level of solarization depends on the brightness and length of the flash as well as on which stage of development is disturbed, the original negative or the paper print. Each will result in different visual effects, including exaggerated borders between areas of high contrast and a heightened metallic appearance.

  • toned (hand colored)

    A toned print has had a colored wash applied to it, overall or in parts, either by brush or by immersion in a watercolor bath. The wash produces tinted effects ranging from subtle shades to dramatic coloring.

  • toning

    Toning is a category of various chemical processes, each of which produces different color or contrast effects by altering the final developed image material. Some papers are self-toning, requiring no additional processing, and others require separate processing steps, either prepared by the artist or formulated by manufacturers, for example in tablet form, to be dissolved in the appropriate solution. The formulation dictates the effects: toning solutions based on gold or selenium intensify the image, impart a cool, purple hue, and give higher contrast, while sulfur yields a sepia color. The chemical reactions improve the stability of the individual image particles, increasing the durability of the print.

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