Photograph Basics

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Origins of Photography and the Variety of Processes | Photographic Materials and Construction | Photograph Care, Handling, and Storage

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Origins of Photography and the Variety of Processes

The word “photograph,” from its roots “photo” and “graph,” literally means to draw or write with light. The term has been loosely applied to a wide variety of light-sensitive imaging processes from 1839 to the present. For most of the 20th century, the word “photograph” most often referred to a print consisting of a silver gelatin image emulsion on a paper support.

Paper-based photos have traditionally been made by transmitting light through a negative image (usually captured on a glass plate or flexible film) onto a sensitized photographic paper, resulting in the familiar positive picture. This process is called “printing.” A nearly limitless number of photo prints can be made from the original negative using this procedure.

Daguerreotypes, ambrotypes, and tintypes (or more accurately, ferrotypes) are non-paper-based images from the earliest days of photography. As these processes do not incorporate a negative that can be used to make multiple positive images, they are often referred to as “camera originals.” Polaroid photos (sometimes generically called “instant photography”) can also be included in this category. Film transparencies, such as the familiar 35mm slide, likewise do not use a separate negative.
 


Photographic Materials and Construction

Photographs consist of an image-bearing layer, usually called an emulsion, and a base material that supports the image. For prints, the support is traditional paper (often called “fiber”) or plasticized paper, referred to as RC (or “resin-coated”). The paper prints are often also adhered to heavier card stock mounts.

The earliest photographic processes used a variety of supports including silver-plated copper sheets (the daguerreotype), glass with a black backing (the ambrotype), sheet metal (the tintype or ferrotype) as well as leather, wood, cloth (sometimes called pannotypes), or even ceramic materials. These images were often purveyed in cases or small albums constructed of a variety of other materials.

The emulsions for negatives were originally supported on sheets of glass. Late in the 1800s, flexible film negative materials began to be developed. In the latter half of the 20th century, flexible films were made of polyester or triacetate plastics, replacing the dimensionally unstable and flammable cellulose nitrate and diacetate products.

Correctly identifying the image process (emulsion) and the base support material or materials is critical to understanding the proper care and storage of a particular photograph.
 


Photograph Care, Handling, and Storage

Handling - Image emulsions are very thin and fragile and easily damaged by mishandling, exposure to contaminants, and poor environmental conditions.

Wash and dry your hands before handling photographs just as you would before handling books, documents, or other cultural artifacts. Photographic emulsions are particularly vulnerable to fingerprints left by the oil and acids on hands, so photos should be handled only by the edges or preferably with clean, white cotton gloves made especially for that purpose.

Photographs should be supported and viewed on a clean, dry, flat surface, such as a table or mat board, to prevent cracking or other mechanical damage.

Light - Light is what makes photography possible and light is also one of the greatest enemies of images. An essential part of the process of making a photo is “fixing” the image to stop its development, but all photos will eventually fade with exposure to light, no matter how carefully the original is made. Dark storage is always the best storage for photos. Damage from exposure to light, especially the ultraviolet portion of the spectrum, is cumulative and irreversible. Unlike living organisms, photographs do not repair or rejuvenate themselves. No amount of dark storage can compensate for past or future exposure to light.

Environment - Photographs fare best in cool and dry conditions. See Environmental Control for more information. Professional curators sometimes refrigerate or freeze materials, but this practice requires very special controls and procedures. Refrigeration and freezing should never be attempted by individuals, as they can easily damage or destroy photographs.

Notations - Correctly identifying and recording the subjects and other data related to images is essential for future interpretation, but marking on the actual photograph should be minimal, if at all, and done with extreme care. Ballpoint, soft tip, or permanent marker pens should never be used on photographs. If necessary, a soft, rounded (not sharp) graphite pencil can be used to mark lightly the reverse side of paper prints in the margin area or near the edge. Too much pencil pressure can emboss the paper and crack the photographic emulsion. Markings should never be made on the emulsion surface of photographs. Matching the photo to a typed or written description of the photo is a much better practice than attempting to record the information on the actual photo.

Storage - Archival supply vendors now stock a variety of quality folders and boxes made specifically for photographs and other archival items. See the FAQs for a list of archival supply vendors.

Generally, storage materials specified as acid-free and lignin-free are recommended for permanent photo storage. Neutral pH rather than alkaline-reserve storage materials are recommended for some photographic processes. Materials designed for photographic storage may additionally be specified as passing the PAT, or Photographic Activity Test.

Common office supplies and fasteners, such as stick-on notes, paper clips, staples, tape, rubber bands, and glue sticks, should never be used in contact with photographs or mounts.

Permanent photographs should never be laminated, or framed in direct contact with glass or other glazing material. See the FAQs for more information about framing.

Do not attempt to open or unroll prints that have been stored rolled as this can irreversibly damage the photo by cracking the emulsion and fracturing the paper support. This is especially common for long, panoramic prints. See the FAQs for more information about managing rolled photographs.

Preservation information provided by the Texas State Library and Archives Commission is intended only as a general guideline for collections care. The Texas State Library and Archives Commission is not responsible for any damage that might occur in the specific application of this information.
 

Page last modified: August 31, 2011