Chapter 16

Archiving Photographic Images

"Spirit Island" by Lydia Richards, Fine Art Photography student Rochester Institute of Technology.

 

Introduction

Archiving images has different meanings to different photographers. To some it means the processes that one must go through to preserve negatives and prints for eternity. To others it means choosing a digital backup system that will be compatible with the ever changing technologies. We will explore both.

Digital Images

Archiving digital images is a necessary task for every photographer, from the amateur using a simple point and shoot camera to the professional using a high-end SLR camera. The digital environment and the many software packages available for image manipulation has brought photography into the hands of everyone, as was the goal George Eastman. However, if your image collection is not properly archived, one disk failure could mean the loss of everything. Likewise, editing an image and writing it back to the same file could also mean the loss of the original image (your digital negative) forever.

There is no set standard to digital archiving. The term archiving in this case is misleading. Technology changes so quickly that maintaining a digital archive is a constant process. Often a digital image archive is a stored on the highest quality affordable technology currently available. Recall in the digital realm we started with floppy disks, then went to zip drives, and are now at DVDs. It would be difficult to find a functional floppy disk drive today. Therefore, a digital archive must be constantly maintained and updated as often as technology dictates. To be successful in this process a workflow should be established and followed. An example is provided in Figure 16-1.

Figure 16-1 Proposed digital archive workflow.

The workflow in Figure 16-1 starts with the capturing of an image. This may seem simple, but there are considerations here. If the camera has multiple file formats, which one should be selected? From a photographer's point of view, the native RAW format might be best for original image capture but perhaps not for long-term storage. We will discuss this further later in this section and additional information can be found in Chapter 3.

Moving the images from the camera to the computer in the next step. The approach provided makes two copies of the images, one in a folder that is set for archive only and one that is for general use. The decision on what file format to use for the image archive must be made.

Archiving the images in the manufacturer's native RAW format is an option, but it carries some risk with it. Currently all major camera manufacturers have their own proprietary RAW format. As they find more efficient methods for creating the RAW image files, the formats change. In the future an image archived in a RAW format may become inaccessible as software support for older formats is discontinued. There has been proposed an OpenRAW format,¹ which is a standard format that would solve this problem. None of the major camera manufacturers have chosen to participate in this format at the time of this publication.

An additional format option that is gaining popularity is the DNG (digital negative) introduced by Adobe in 2004. This is a royalty-free RAW format that has been adopted by some of the bigger camera manufacturers.

Choosing a file format that compresses the data will save space, but the original image data can never be recovered, which could result in a loss of image quality and the ability to effectively enhance the image. There are two common file formats, tiff and JPEG 2000 without compression that will preserve the original digital data and have been standardized industrywide. The use of a common standardized format would reduce the likelihood of having to reformat images in the future.

The last step in archiving digital images is to make copies of the data. There are many options available today. Two copies should be created, one to keep local for easy access and one to store at another location to prevent the loss of all data in the event of a local catastrophe such as a fire. Local storage options such as placing the data on a hard drive or RAID (redundant array of independent disks) would allow the easy retrieval of original data if needed. The need for easy access is important as everyone will occasionally write over original data or delete a file by mistake. The use of CDs or DVDs is a common choice for offsite storage, as they are easy to transport. The lifetime on these types of media range from 20 to 50 years if stored as the manufacturer suggests.

The key to successfully creating and maintaining a digital archive is to develop a workflow and follow it. The ability to have the original data exist in several locations ensures that a complete loss of data is unlikely.

Silver Image Archiving

Before we discuss the process of archiving silver-based images, we must briefly discuss the development process and the chemical processes involved.

 

Stop Baths

After removing film or paper from the developer it is placed in a stop bath. A stop bath consists of a mild acid, with a pH of 3 to 5, that neutralizes the alkali of the developer and stops development. An acid fixer also provides stopping action but after a quantity of developer has been carried over to the fixer, the acid is neutralized, the aluminum of the hardener will precipitate out as a sludge, and the stopping action is no longer precise. A water rinse before either the stop bath or the acid fixer will remove some of the developer, and prolong the life of either, but then the stopping action is drawn out and imprecise. A stop bath may also contain some hardening agent, and thus becomes an acid hardening stop bath. The most commonly used stop baths consist of 1.4-4.5% solutions of acetic acid, although a solution of sodium or potassium bisulfite is sometimes used. Some contain other additions.

 

Dichroic Fog

A fixer whose acid strength is at or near exhaustion will no longer effectively stop the developing action. As a result, some development will proceed at the same time as some silver halide is being dissolved by fixation, and dichroic stain, which is mostly silver in the colloidal or near-colloidal state, will be produced. Dichroic means that it has two different colors, one by reflected light and the other by transmitted light.

 

Fixing Baths

A fixing bath converts the relatively insoluble silver halide in the film or paper into a soluble complex of silver that can be washed out of the emulsion layer, baryta layer, and paper fibers, to make the negative or print stable. Otherwise, the undeveloped silver halide would not only reduce the contrast of a negative, but it would darken in time and destroy the image. Sodium, ammonium, or (sometimes) potassium thiosulfate are the compounds most commonly used in fixing baths, although sodium thiocyanate and sodium cyanide have been used. (The latter is a hazardous compound and therefore is not recommended for use in photography.)

 

When a fixing bath is used to fix films or prints, silver ions accumulate in the solution, which exert a force in the opposite direction and thus slow down the rate of fixation. If this accumulation is carried far enough, a point is reached where the soluble complex is not completely formed in the time allotted to fixation. If the fixing time is increased, the insoluble complex is adsorbed to the gelatin of the emulsion, the baryta coating if there is one, and the fibers of the paper base. The insoluble complexes are thus not removed by washing, and the silver can later be reduced by environmental factors to produce unwanted color and/or density. The presence of this reduced silver can affect the metallic silver image and cause it to become sulfided, thus changing color and losing density. Therefore, to ensure stable photographic images, it is important that the fixing solution not be worked beyond its capacity. The use of a two-solution fixing technique, whereby the prints are first bathed for a time in a fixing solution, then transferred to a second, fresher fixing solution, assures that the silver halide is converted to a soluble complex. After some time, the first fixer is discarded (or consigned to silver recovery), the second fixer becomes the first fixer, and a fresh fixing bath is added.

 

Washing

After fixing, photographic materials have to be washed to remove any of the fixing chemicals remaining as well as the silver compounds that have been formed during the fixing reaction. The problem is not a simple one. The chemical reactions leading to a soluble silver complex pass through steps in which insoluble complexes are formed, and these have to be fully converted to the soluble compounds. In addition, these complexes have a pronounced tendency to adhere to or be adsorbed by the fibers and baryta coatings of ordinary papers (see Figure 16-2). Films and polyethylene- or resin-coated (RC) papers do not generally present this problem except to the small extent that it may occur in gelatin coatings. For these reasons, the fixing step should be for the minimum time that will ensure that the reaction goes to completion to prevent any appreciable adsorption of the chemicals.

As the fixing process continues, and more silver complexes accumulate in the fixing bath, the tendency increases for the reaction to be forced in the reverse direction. In general, the fixing bath will perform well when the total amount of silver (in the form of ions from residual silver thiosulfates) in the bath is below 2.0 grams/liter. Films and resin-coated papers are readily washed, as they do not have fibers or baryta coatings exposed to the solutions for adsorption to take place. Fiber-base papers may not be completely washed even after 60 minutes of washing under ideal conditions, whereas films are usually washed in 20 to 30 minutes under similar conditions and resin-coated papers in 4 minutes, provided the wash-water flow rate is sufficient to give the required number of changes. The specific gravity of a typical fixer is in the vicinity of 1.18. However, with a reasonable flow of water the fixer does not have a chance to settle to the bottom of the wash tank.

Figure 16-2 Baryta-coated fiber-base papers retain some residual hypo and silver complexes. Films do not contain a baryta coating or paper fibers, and RC-base papers have protective resin coatings on both sides of the paper base.

Preparation for Drying

After films or papers are washed for the time necessary to remove residual thiosulfate or thiosulfate-silver complexes, they should be carefully dried. This aspect of the photographic process is often neglected to the extent that it subtracts substantially from the quality and acceptability of the final product. Fiber-base papers absorb considerable water during washing, and this has to be removed in the drying process. RC (resin-coated) papers, on the other hand, absorb very little water, and this is restricted to the thin emulsion and NC (non-curl) coatings. These materials dry very rapidly—in a matter of a few minutes.

Films washed in clean water can be hung up to dry without wiping. However, if drops of water are allowed to remain on the film, drying marks or deformities in the image will form because of differential shrinking of the gelatin around the edges of drops on the emulsion side that will be difficult, if not impossible, to remove. Excess water droplets and sediment in small amounts can be removed with a clean moist sponge or chamois by carefully wiping the surfaces, but if care is not used, this procedure may put more contamination on the negative than it removes.

In large laboratories where the film is processed in a serpentine fashion in continuous lengths, excess moisture is blown off by an air jet or squeegee. Water spots on sheet films and individual rolls can be avoided by using a wetting-age nt bath before drying, which spreads the surface layer of water so that no droplets are formed. Kodak Photo-Flo™ is one such product. This bath, if made with filtered or otherwise clean water, can also serve as a rinse to remove some sediment. Gently rubbing the film surfaces as they are removed from the wash water can dislodge particles that may tend to cling to them.

Drying Films

It is best to dry films at room temperature—but this procedure may require an inconveniently long time in some situations so that heat is often applied, along with air circulation, to hasten the drying process. At the start of drying, relatively warm air can be used, as evaporation of the moisture in the film has a cooling effect. As drying progresses, high temperatures should be avoided. If the temperature is too high, drying will become excessive, and the film may become brittle and curl excessively. Other damage to the film may also occur. The air should be filtered to prevent the accumulation of dust on the film surfaces. A large volume of relatively pure air can carry a substantial number of particles that could be attracted to the wet film. This attraction can be accentuated by the electrostatic charge built up in the film by the air flowing over its surfaces.

Figure 16-3 Paper drying

Drying Prints

Similar precautions apply to the removal of excess water from the surfaces of prints that are to be dried. Print-drying machines usually have squeegee rollers at their entrances that remove excess surface water. RC or resin-coated papers carry relatively little water and can be dried quite rapidly, within a few minutes without heat, after the excess water has been removed. Fiber-base papers, on the other hand, can carry a relatively great load of water, which has to be removed. Air drying the prints at room temperature on clean cheesecloth or racks is probably the least destructive to the image and the physical quality of the prints. However, if the relative humidity is high, this kind of drying process is apt to be excessively long. For this reason, most photographic installations make use of heat dryers of one form or another (see Figure 16-3).

Preservation of Photographs

The chief factor in the preservation of silver photographic images is the total removal of silver complexes and hypo from the print by washing, before drying. After that it is important that the print not be exposed to any contaminant that would react with the silver image. The choice of adhesives for mounting, if the print is mounted at all, is important. Some kinds of glues and pastes, especially those that might contain sulfur, should never be used. Hygroscopic materials (substances that absorb water from the air) should not be used. Dry-mounting tissues especially designed and marketed for mounting photographs are generally acceptable. But even this type of mounting may eventually detract from the value of the photograph if it becomes a collector's item. The best recommendation seems to be that of using archival materials (mounting and matting boards, and cloth tape) to suspend the print under a mat, then in a frame under glass for display. If the mat has to be replaced after some handling, it is a simple matter to remove the print and re-mat it.

Sometimes the photographic print is only an intermediate image for use in preparation of plates for printing in catalogs, magazines, or newspapers, and once these plates have been prepared, the photograph is no longer needed. In the motion-picture industry, the release prints need only last as long as the physical capability of the film to sustain screenings—about 500 to 1000 projections—after which it is destroyed. However, if the images are expected to have some value in later years, other precautions have to be taken. The photographer will need to make sure the print is made to have archival permanence, and the motion-picture companies will have to have their prints made on film with dyes that will hold up under long-term storage, or have separations made on black- and-white film that can be stored and then brought out for regeneration of the color films at a later date.

Storage containers, mat boards, and mounting boards are potential sources of agents that are deleterious to photographs. For this reason, if photographs are to be stored for any time, they should be packed in properly designed containers made of inert materials. Old film and paper boxes should not be used; neither should wooden and cardboard cases. Metal cases coated with paints that do not give off any fumes, or cases made of inert or acid-free-board, should be used. Mount and mat boards should be inert and acid-free; that is, buffered to a slightly higher than neutral pH for black-and-white photographs. However, there may be some question in using this type of material for color photographs, since most of these dyes may survive best under slightly acid or nearly neutral conditions.

It is important that the storage area's atmosphere be maintained with moderate or lower temperatures, and low relative humidity (below 50 percent). The cyclic effect of day and night conditions—wet then dry, winter then summer—contributes more to rapid deterioration than when these conditions are maintained at a desirable low humidity and temperature with a small cyclic variations.

REVIEW QUESTIONS

1. Failure to use a stop bath for quantity processing of prints may result in …
   1. fogged prints
   2. contrasty prints
   3. discolored prints
   4. sludge in the developer
   5. sludge in the fixer
2. The pH values of stop baths are usually in the range of …
   1. 2 to 4
   2. 3 to 5
   3. 4 to 6
   4. 5 to 6
3. In the two-solution fixing procedure, the fresher fixing bath is in the …
   1. first position
   2. second position
4. The recommended method of extending the life of a fixing bath is to …
   1. heat the bath to 100° F
   2. add replenisher
   3. remove the silver
5. Hypo eliminators work on the principle of …
   1. causing thiosulfate ions to precipitate
   2. neutralizing the static electrical charge on the thiosulfate ions
   3. converting thiosulfates to sulfates
   4. producing a molecular oscillation
6. With respect to image stability, toned images …
   1. are more stable than silver images
   2. are less stable than silver images
   3. vary considerable in stability
7. If a negative of a normal-contrast subject that was correctly exposed but overdeveloped is to be reduced, it should be reduced in a …
   1. proportional
   2. sub-proportional reducer
   3. super-proportional reducer

fn1 ¹ For more information see http://www.open-raw.org