Negatives
A photographic image is formed by the action of light falling onto a base material which has been coated with a light-sensitive emulsion. This latent image may then be ‘developed’ and ‘fixed’ by further chemical processing. The emulsion coating in most modern photographs is usually gelatine, which incorporates either silver halide salts to form black and white images, or dyes or pigments to form colour images. The base can be made from any material that can be coated with an emulsion, but the most common bases are paper and film.

Negatives are reversed polarity images from which positive prints are produced which can be colour or black and white, and in a range of sizes. Early negatives were on glass but for most of the twentieth century flexible film bases have been used. Film-based negatives can be in either sheet or roll form. Historical photographs may be daguerreotypes, using copper sheets and mercury vapours, or albumen prints made on very thin papers with an emulsion derived from egg whites. Early photographs were also made with supports of glass and metal and collodion emulsions. In the early 1850s, the wet collodion negative was introduced. A glass plate was treated with collodion and silver nitrate, and exposed and processed while still wet. This required the photographer to apply the coating and develop the negative on-site. Collodion can be identified by its uneven surface coverage and slightly green toneI Gelatin dry plates of the 1870s soon replaced the wet collodion negative. Gelatin dry plates were machine made, producing a smoother plate with a more even emulsion than collodion plates. By the late 1880s glass negatives were replaced by a clear plastic film made from cellulose nitrate..In 1889, Kodak introduced nitrate film, made of cellulose nitrate plastic, which could be wound in rolls to improve portability. Nitrate was used to produce sheet film, as well as motion picture film. Unfortunately, cellulose nitrate proved to be highly flammable, especially in reel format; it also became acidic when poorly stored.

These problems led to the development of "safety film" in the 1930s. This was superseded in the 1930s by 'safety film' on cellulose diacetate base and again in the 1950s by cellulose triacetate. Triacetate is still used as a film base today in conjunction with polyester film which was introduced in 1960.Made of cellulose acetate plastic, this film is harder to ignite and is self-extinguishing. Unfortunately, early safety film is also impermanent. As cellulose diacetate (the earliest form) degrades, it generates acetic acid that smells like vinegar. This phenomena is sometimes refered to as the "Vinegar Syndrome" in the preservation literature. Its gases can damage paper or photographic collections in the proximity of the degraded film. In 1947 Kodak introduced another type of safety film, cellulose triacetate. Although it is much more stable and still used today, it also has inherent problems and unless stored under optimum conditions may eventually exhibit the same problems as earlier films.

Polyester film was developed for use as a film base after World War II and is used for most roll film, movie film, and sheet film today. It has demonstrated excellent dimensional and chemical stability and is the plastic film base of choice whenever long-term preservation is a concern. Film-based negatives can be badly damaged by exposure to dust, dirt and fingerprints, which spoil the image quality and may also act as a moisture absorbent and promote mould growth.

Nitrate and acetate film bases present particularly serious problems in collections of archival film. The degradation processes that arise in these types of film cannot be halted and ultimately lead to irretrievable image loss, sometimes over very short periods of time. Should you find nitrate or early safety film in your collection, segregate them from other materials as quickly as possible. These materials should be stored in buffered paper envelopes and boxes and kept in a well ventilated area. Both nitrate and early safety film should be monitored on a regular basis and ultimately duplicated onto a stable polyester film base. Institutions should give highest priority to duplication of film that shows early signs of deterioration, since deterioration can proceed very quickly once begun. Nitrate and acetate safety film deteriorate at about the same rate, so one film type need not necessarily be duplicated before the other Nitrate film is classified as a hazardous substance as it can self-ignite in some circumstances and is difficult to extinguish once it starts to burn. It must be stored separately from other collection materials, in a designated area that firefighters can identify. As nitrate film deteriorates it produces nitric acid fumes which will damage other records stored in the vicinity and can cause health problems for staff working with the material. Deteriorated nitrate sheet film at this stage cannot be copied.

Nitrate film was widely used before the 1940s and can be identified by the following characteristics:

Sticky or greasy surface

Dark yellow or brown all over staining

Strong bitter or acrid smell.

Cellulose acetate film is also known as ‘safety film’ because it was developed to avoid the high risks associated with nitrate film. It was widely used until the 1970s and is still commonly used in some photographic applications. Once acetate film starts to degrade it gives off acetic acid vapour, a type of deterioration commonly known as ‘vinegar syndrome’. As the deterioration progresses the base material shrinks and the emulsion layer starts to warp and wrinkle. Acetate film includes both diacetate and triacetate bases. Triacetate is relatively more stable than diacetate, but it too may develop vinegar syndrome as it ages. Acetate film was produced after the 1940s. Degrading acetate film can be identified by the following characteristics:

Noticeable vinegar smell

The base is warped or wavy

The emulsion contains bubbles, wrinkles or crystalline deposits.

Photographic negative collections present unique problems to institutions and collectors. Glass-plate negatives can break easily, cellulose nitrate and the various cellulose acetate negatives will self-destruct over time, and negatives are generally difficult to read and to access. The duplication of negatives is one preservation option available to help alleviate the problems. Duplication can preserve a deteriorated image, protect a negative from excessive handling, or improve access to a collection. However, duplication has limitations: each successive generation of an image loses quality and detail. Therefore it is critical that duplicate negatives be printed on stable materials and have the highest quality image reproduction. Duplicate negatives should be on modern polyester film and duplicates should have, as close as possible, the same density range and the same amount of detail as the originals.

Color photographs, negatives, slides, and motion picture film are found increasingly in library and archival collections. Most date from after the mid-1930s, when chromogenic development was first used by Eastman Kodak and Agfa. Earlier color processes, some of them on glass, are less commonly found, among them autochromes. The most significant fact about the preservation of color materials is that they are inherently unstable. Most dyes used in color emulsions fade within a few years if exposed to light. Many will fade within 35 years, even when stored in the dark. While their stability has improved in recent years, color materials have a far shorter lifespan than black-and-white materials.

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Storage
Photographic material should be stored in a clean, dark, climatically-controlled environment. Materials degrade quicker when exposed to ultraviolet light. Fluorescent tubes which are low in ultraviolet light should be used wherever possible in storage areas. Ultraviolet light can be easily measured with a light meter, and levels should not exceed 75µW/lumen. Lights should be turned off whenever possible. Storage areas should not have windows, but if they do they should be covered with curtains or blinds.

Insects and rodents once attracted to a records storage area may start eating the records, so:

do not eat in storage areas

keep surfaces (floors, tops of shelves) clean

bait regularly for rodents and fumigate annually for insects.

Storing photographic materials under poor environmental conditions can result in irreversible damage. High temperatures accelerate deterioration, causing fading and discoloration, especially when relative humidity (RH) is also high. When combined with air pollution, these conditions may cause silver images to oxidize, color dyes to shift and fade, and mold to grow. Mold may be impossible to remove without damaging the photograph.

High RH levels can soften emulsions and allow dirt to become embedded, making the images vulnerable to mechanical damage. Ferrotyping can occur at high RH levels, and softened gelatin can adhere to plastic enclosures. High RH is also a major cause of highlight yellowing of albumen prints. Conversely, extended storage at low RH can cause photographic emulsions to shrink and crack, supports to curl, and mounts to warp.

Exposure to light can also damage photographic prints, causing them to fade and become brittle. Well-processed black-and-white silver gelatin prints are relatively stable at moderate light levels. However, color prints and early black-and-white images, especially salted paper and albumen prints must be protected from unnecessary light exposure. Resin-coated or "RC" papers are especially vulnerable to light, developing a metallic sheen known as "bronzing."

While these photographic defects appear quite different, they are all caused by essentially the same chemical reaction. The enclosure paper, album or mat material releases oxidizing gases which react with the silver image. The silver oxidizes, causing it to be invisible, and more important, it becomes mobile and can literally move to another location in the photographic layer. This oxidized silver can then be reduced forming visible metallic silver again but this time it is in an unwanted area such as in redox blemishes or as a mirror on the surface of the image layer.

Consequently a very important property for an enclosure material is whether it will release oxidizing gases over time. This is a difficult property to determine since it is a predictive characteristic which can only be evaluated by an accelerated test. ThePhotographic Activity Test (PAT) involves incubating the enclosure material at elevated temperature and humidity in close contact with several sensitive detectors. Oxidizing gases that are released react with these detectors and the resulting changes can be measured. These measured changes are the degree of fading and appearance of mottle in a silver detector and the degree of stain growth in a non-image detector. Materials pass this test when the changes are less than the limits arrived at from practical experience. The test can be performed by several testing laboratories experienced in this field as well as in a number of government laboratories.

The method of packaging photographs will depend on the particular material and the use for which it is required. Photos may be kept in reference albums, enclosures, boxes and folders. Very fragile items such as glass plates, daguerreotypes or large presentation prints may require customised packaging. Archival quality packaging which passes the Photographic Activity Test should be used for long-term storage. If plastics are used they should be polyester or polypropylene - PVC should not be used at all. Archival quality paper or board should be used for envelopes, files and boxes.

Prints and negatives should be individually packed in bags or envelopes or placed in individual pockets in an album page. Loose material should be packed in small groups in archival files or folders and then boxed. If paper-based albums are used the support and boards should be of archival quality, with all pages interleaved and the images held by photo corners.

Each item to have its own enclosure. This reduces damage to the photograph by giving it protection and physical support. Acceptable storage materials can be made of either paper or plastic. Because paper enclosures are opaque, the photograph must be removed from the enclosure when it is viewed; clear plastic enclosures have the advantage of allowing researchers to view the image without handling it, thus reducing the possibility of scratching or abrasion. Paper enclosures should be acid and lignin free. Plastics suitable for photographic storage are polyester, polypropylene, and polyethylene. Polyvinyl-chloride should be avoided at all times. Both paper and plastic enclosures should meet the specifications provided in the American National Standards Institute (ANSI) Standard IT 9.2-1998 and should pass the Photographic activity test (PAT).

Recommended Storage Conditions:
Photographs are extremely sensitive to atmospheric pollutants. Particulate pollutants may cause abrasion and attract mold or insects. Sulfur compounds form silver sulfide in moist air, which can cause fading. Indoor pollutants such as paint, plywood and cleaning supplies may also result in staining or fading. Clean, filtered air and regular housekeeping will combat pollutants

.Moisture in the air may combine with processing chemical residues to cause fading, yellow and brown stains, or silver mirroring of prints and negatives. High humidity may promote mould growth, particularly in gelatine emulsions which provide an excellent nutrient for mould, while low humidity can cause the emulsion to crack and the support to become brittle.

Photographic materials must not be stored in hot places or near heat sources. Heat accelerates chemical reaction, causing the rate of deterioration to double with each temperature increase of 18 degrees F. Conversely, deterioration of some materials can be slowed by storing them at low temperatures. Shelves should be made of coated metal. Wooden shelving should be avoided, as it can release harmful vapours, can contribute to the spread of fire and may harbour insects.

A frost-free refrigerator is a simple way to store color negatives, slides, prints, and motion pictures at low temperature and relative humidity. Older manual-defrost refrigerators should NOT be used since they have high relative humidity levels. Cellulose nitrate film should not be kept in refrigerators, but should instead be stored in special explosion-proof freezers.

Photographic prints and films should be packaged in envelopes, boxes, or polyethylene bags to protect them from humidity fluctuations during defrost cycles or when the door is opened.3 The refrigerator should not be too tightly packed so that air can circulate. Cold storage should be used only for limited access collections, since the climate inside the refrigerator cycles each time the door is opened. Humidity levels in the refrigerator should be tested regularly with a dial hygrometer. Photographs removed from the refrigerator should be allowed to warm up for 2-3 hours before unwrapping. Exhibition times for original materials must be strictly limited; copies should be made for display purposes whenever possible.

Most storage solutions will require some compromise between what is ideal and what is feasible. It is best to separate photographic prints from negatives, if at all possible. This will prevent contamination of prints by acidic gases and will make it easier to monitor the condition of the film. Storing similar sized items together is also recommended, so that good support is ensured and distortion prevented.

Photographic sheet films, such as x-rays or portraits, are stored in paper envelopes. This is also true for photographic plates. Microfilms in roll form have been kept in cardboard boxes while photographic paper prints are mounted on paper mats or on paper pages in albums. In all these applications there have been numerous examples where the paper enclosure caused unwanted and deleterious changes in the appearance of the silver image. These changes can take several forms. In some cases the silver image has turned brown and faded. In other materials, particularly photographic paper prints, a silver reflecting mirror appeared on the print surface, with a resulting deterioration of the print appearance. Image degradation in microfilms was manifested by the appearance of small red spots which could affect legibility. These spots are well known in the industry as redox blemishes and were particularly prevalent when microfilm was stored in cardboard boxes.

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Paper Enclosures
The quality of pulp used to make storage paper is important to the preservation of photographs. Groundwood, from which many modern papers are made, contains lignin, which produces acids rapidly. Papers described as lignin-free are produced from cotton or linen (containing little lignin) or from wood fibers that have had the lignin chemically removed. Lignin-free buffered and non-buffered (neutral) paper enclosures are available.

The term acid-free is widely used to refer to archival-quality paper materials constructed of either neutral or buffered paper. A more precise distinction should be made between the two. Neutral enclosures, constructed of paper in the neutral pH range (6.5-7.5), do not contain acids that will damage photos stored in them, but have a limited capacity to neutralize acids from the environment or from paper deterioration. Buffered paper enclosures (pH 7.5-9.5) contain an alkaline material that neutralizes acids as they form. In the past, conservators have recommended the use of neutral paper enclosures for storage of color images, cyanotypes, and albumen prints. It was believed that these processes were sensitive to the alkalinity in buffered papers. Recent research has indicated that buffered storage enclosures are not detrimental to photographs. Therefore whether paper is neutral or buffered is not a major criterion for choosing an enclosure.

Labels such as acid-free do not guarantee that a material is safe when used with photographs. Even archival papers may be harmful to the photographic image. The only way to be certain of the inertness of the paper is to have materials undergo the Photographic Activity Test (PAT) as specified in ANSI NAPM IT9.16-1993.2 The PAT has two components: a test to detect image fading resulting from harmful chemicals in enclosures; and a test to detect staining reactions between enclosures and gelatin. Consumers should contact suppliers of archival materials to see if their products comply with ANSI IT9.16-1993, and have passed the Photographic Activity Test.3

When PAT test results are not available, purchase materials from suppliers familiar with the special needs of photographs, and choose enclosures that are lignin-free, 100% rag, and not highly colored. Glassine enclosures are not recommended. Glassine paper is made with short, brittle wood pulp fibers, which are prone to rapid decay. Often in the pulp are additives which increase the flexibility and translucency of the paper. Therefore, glassine has three sources of potential harm to photographs: possible impurities from wood pulp, possible harmful additions, and deteriorating paper fiber.

In recent years, MicroChamber and other pro-active storage papers have become available. These scavengers contain activated charcoal and zeolites, which react with polluting gases, trapping them and removing them from the environment. These papers can moderate the destructive effects of pollutant gases. They may be particularly beneficial in an uncontrolled environment, especially if the collection contains color photographs, nitrate film, or early safety film.

Advantages and Disadvantages of Paper
Paper enclosures are opaque, protecting the object from light. However, this makes viewing difficult, requiring the removal of the object from the enclosure. This increases damage from handling, abrasion, and fingerprinting, especially in heavily used collections.Paper enclosures are porous, protecting the object from the accumulation of moisture and detrimental gases. Paper enclosures are generally less expensive than plastic enclosures.Paper enclosures are easy to write on.

Seamed Paper Envelopes. An envelope is an enclosure with one open end; it may have a protective top flap. The seams in paper envelopes should be located at the sides and, if unavoidable, across the bottom. Any adhesives used in construction should be non-acidic and unreactive with silver. Most envelopes come with a thumb cut, but those without are preferred. Thumb cuts allow air to touch the photo, and encourage users to grasp the photo and pull it from the sleeve. Rather, to remove a photo, push in slightly on the sides of the envelope, and tap the photo out, handling only the edges. With seamed envelopes, the photograph should be inserted with the emulsion side away from the seam.

Seamless Paper Envelopes. The seamless envelope does not have any adhesive. The envelope is formed with three or four flaps which fold over to produce a pocket. The fourth flap, if present, closes the envelope completely, protecting the object within from dust and dirt. The construction of this envelope encourages the user to place the object on a flat surface to open it, which can be an advantage for brittle or fragile items such as glass-plate negatives. Also, this type of enclosure is constructed so that it can compensate for the thickness of an object.

Paper Folders. A folder is a sheet of paper that is folded in half. It is closed on one side only and must therefore be kept in a properly fitted box to hold the image effectively. If a paper folder is used for vertical storage in files, the photograph stored inside must be well supported to prevent sagging or curling. Folders are simple to make and are most useful for large or mounted items.

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Plastic Enclosures
Plastic enclosures of archival quality may be made of polyester, polypropylene, or polyethylene. They should not be coated or contain plasticizers or other additives. Polyester is the most inert, dimensionally stable, and rigid of the three. It can generate static electricity, which attracts dust, and it is expensive. Polyester enclosures should be either DuPont Mylar D or ICI Melinex #516. Polypropylene is almost as rigid as polyester when it is the untreated "oriented" polypropylene used in sleeve formats, but is soft when it is the surface-treated polypropylene used for ring binder storage pages. Because specifications on the surface coatings of the soft polypropylene are proprietary information and not readily available, this material cannot be properly evaluated. Polyethylene is the most easily marred and least rigid of these plastics. High-density polyethylene is a translucent, milky plastic which is naturally slippery. Low-density polyethylene, the clear polyethylene used in ring-binder storage pages, has incorporated antiblock and antislip agents which could be problematic.

Plastic enclosures made from polyvinylchloride (PVC) are unacceptable for archival photographic storage. This plastic, often referred to as "vinyl" by suppliers, is not chemically stable and will cause deterioration of a photograph over time.Plastic Envelopes. Plastic envelopes normally have heat-sealed seams, which eliminate any potential problem with adhesives. Both polyethylene and polyester envelopes are marketed by conservation product suppliers.

Plastic Folders. These may be successfully used in conjunction with paper envelopes, the polyester folder protecting the image from handling whenever it is removed from the paper envelope.

L-Velopes. These are a combination envelope-folder, being an envelope sealed on two adjacent sides. This allows for easy insertion and removal of objects, and provides more support than a folder. This design is particularly useful for smaller-format images.

Plastic Sleeves. Often these sleeves are enclosures open at two opposite sides made from polyester or polypropylene. Usually, these sleeves are a one-piece construction with a self-locking fold on one edge (also called top-flap sleeves). This fold provides for easy insertion and removal of the photograph with no abrasion to the image. However, when these sleeves are stored in groups, the folds can lock onto adjacent sleeves, making retrieval of the photographs difficult.

Polyester Encapsulation. Polyester encapsulation encloses a photograph between two sheets of polyester, sealed on all four sides with either double-sided tape or a special polyester welding machine. Encapsulation provides physical support and protection from the environment. It is useful for storing fragile prints, especially those that are torn. Encapsulation is not recommended for photographs adhered to poor quality mounts or for contemporary color photographs.

Ring-Binder Storage Pages. These pages are made to fit three-ring binders with slipcases. They are available in a wide variety of formats, sizes, and materials, including polyester, polypropylene, and polyethylene. They are an excellent alternative for small, concentrated collections of uniform size.

Polyester Sheet - Matboard Folder. These folders are made of a sheet of polyester and a sheet of matboard of the same size, attached together along one long edge with double-sided tape. The matboard gives needed support and the polyester allows the image to be easily viewed. These folders should be stored flat. They are particularly useful for storage of oversized photographs or photographs on rigid mounts. In time these folders will probably need to be replaced or the double-sided tape will break down, releasing the polyester from the folder and possibly sticking to the object.

Polyester Sheet Within a Paper Folder. This enclosure consists of a paper folder with a polyester sheet attached along an inner edge, opposite the center fold. The attachment is made with double-sided tape. The polyester holds the object in place and protects it from dirt and handling, but allows for easy viewing and removal. The paper folder provides support to the image and protects it from light. These folders are especially useful for small, fragile prints. However, over time the double-sided tape will release, necessitating folder replacement.

Advantages and Disadvantages of Plastic
Plastic enclosures have the great advantage of allowing an image to be viewed without being removed from the enclosure. This greatly reduces the chance of abrading, scratching, or fingerprinting the photograph, especially in heavily used collections. Plastic enclosures can abrade and scratch photographs during insertion and removal. Matte or frosted surfaces are not recommended as they are abrasive to emulsions. Low-density polyethylene also can have problems with abrasion. Abrasion can be avoided by minimizing the removal of photographs from enclosures, using properly designed enclosures (such as self-locking sleeves), or using plastics that are naturally slippery (high-density polyethylene). Moisture and sulphides in the environment react with photographs to hasten their deterioration. Plastic enclosures protect the object from the atmosphere. but plastic enclosures can trap moisture and cause ferrotyping (sticking with resulting shiny areas) of the image. This is a particular threat in storage environments with high relative humidity or in the event of a disaster involving water. Those plastics more prone to ferrotyping include surface-treated polypropylene and low-density polyethylene. Plastic enclosures can be difficult to write on. Plastic enclosures can be flimsy and may require additional support, such as archival-quality Bristol board. Any information that should accompany the image can be recorded on this board. Plastic enclosures with low melting points (polyethylene) can melt during a fire, adhering themselves irreversibly to the materials stored inside them.

Once materials have been properly housed in folders, sleeves, or envelopes, they should usually be stored flat in drop-front boxes of archival quality. Glass plate negatives are an exception and should be stored vertically in order to prevent breakage of plates stored on the bottom of a pile. The boxes should be housed on metal shelves or in metal cabinets. Where possible, items of similar size should be stored together; the mixing of different sizes can cause abrasion and breakage, and can increase the risk of misplacing smaller items. Regardless of the size of the photograph, all enclosures within a box should be the same size and should be the size of the box. Boxes should not be overfilled.

Horizontal storage of photographs is usually preferable to vertical storage, since it provides overall support and avoids mechanical damage such as bending. Vertical storage, however, may make access to the collection easier and decrease handling. With vertical storage, photographs should be placed in acid-free file folders or envelopes that are themselves housed in hanging file folders or document storage boxes. Overcrowding should be avoided. The use of hanging file folders will prevent photographs from sliding down under each other and will facilitate their handling.

Special care must be given to the storage of oversized photographic prints mounted on cardboard. This board is often acidic and extremely brittle. Embrittlement of the support can endanger the image itself because the cardboard may break in storage or during handling, damaging the photograph. Such prints must be carefully stored, sometimes in specially made enclosures. They should be handled with great care.

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Duplication
Duplicate negatives that show any signs of deterioration. Deterioration includes characteristics such as breakage, flaking, fading, discoloration, warping, bubbling, channeling, or a strong odor.Negatives that are particularly susceptible to deterioration. Nitrate film negatives. Insurance companies and fire departments often have specific and expensive regulations governing storage of nitrate film. If these regulations cannot be met, duplication and disposal of the film may be necessary. Original negatives that are frequently printed or handled. Negatives with high intrinsic value.

Preparing Negatives for Duplication
In a collection, number the negatives and their enclosures consecutively and store them in numerical order.Number the original negatives on the base (non-emulsion) side in a non-image border area using a fine-point permanent marker. Once the images are duplicated, the numbers will appear on the duplicates, eliminating the need to spend more time numbering.Some nitrate films are edge-marked "nitrate." This identification should be masked out to prevent its duplication onto safety film.

Prints and Copy Negatives
The simplest way to duplicate negatives is to make a print and then to photograph the print using a large-format camera (4" x 5" or larger) to produce a copy negative. The advantages of this method are cost and convenience. Most museum darkrooms or local photo labs should be able to do the work with little or no investment in equipment. Further savings may be achieved by using already existing prints for copying. Where no original negatives exist, copying existing prints is the only available option. The disadvantage of this system is loss of detail in both the print and the copy negative. A print always has detail loss and a compressed tonal range when compared to the original negative, and further detail is lost when the copy negative is made.

Direct Duplicate Negatives
Eastman Kodak Professional Black & White Duplicating Film #SO-339 is designed for directly duplicating negatives. This is a one-step process yielding a negative from a negative. Duplicating film has high resolution, minimizing loss of image detail during copying. Also contrast can be manipulated during duplication to salvage some problem negatives. However, since the film is blue sensitive, minimizing staining can be problematic. This film can be difficult to work with, making accurate tone reproduction hard to achieve. Contact-printed direct duplicate negatives are laterally reversed, therefore the image can mistakenly be printed backwards if the photographer is not aware of the nature of the material.

If the original negatives are disposed of, the duplicate negatives become the masters. This is a major disadvantage since whenever an image is needed the master is used for printing, exposing it to the likelihood of eventual damage.

Interpositive Duplicate Negatives--Contact Duplication
The original negative is contact-printed onto film to produce an interpositive (a positive image on film). The interpositive is then contact-printed onto film to produce the duplicate negative. This process provides the most accurate tone reproductions possible. Problems in original negatives can often be corrected by using selected films and filters to reduce staining during the production of the interpositive. The disadvantages of this system are the higher production costs, the complexity of the procedure, and the added storage space required for the multiple duplicates. However, this method results in two duplicates for relatively little additional cost; the interpositive becomes the master and the duplicate negative becomes the use copy.

Interpositive Duplicate Negatives--Reduced Format, Long Roll Systems
Original negatives are copied onto 5-inch/105mm, 70mm, or 35mm roll film using a camera to produce interpositives (a positive image on film). The interpositive is then contact-printed onto film to produce the duplicate negatives. This system provides accurate tone reproduction. Also, problems in original negatives can often be corrected with the use of selected films and filters to reduce staining during the production of the interpositive. These systems provide easy access to collections. They have high production capabilities and lower production costs, and they require less storage space. However, with reduced-size duplicates there is usually some loss of image detail, proportional to the amount of reduction. As with contact interpositive duplicate negatives, this system results in two copies; the interpositive becomes the master and the duplicate negative the use copy.

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Handling and Care
Some photographs are very light sensitive, and can fade or darken with excessive light exposure. Additionally, film or prints that have been poorly processed may develop instability of the base material and staining or bleaching of the image. Deteriorated photographs that are extremely valuable as artifacts may require conservation treatment by a professional photographic conservator. However, expensive conservation treatment is neither feasible nor cost-effective for most deteriorated photographs. Instead, educating staff and users in proper care, handling, and storage will have the greatest positive impact on the long-term preservation of entire collections.

Use lint-free cotton gloves should be used at all times when handling photographic material.

Labels and identification stamps should never be applied directly to photographic material. Identification should be on the packaging. Pencil or an appropriate pigment pen can be used on the border of slides. Never write on the back of photographic prints as this will damage the image.

Never use metal pins, staples, paper clips, rubber bands or adhesive tape with photographic materials.

Viewing equipment should be well-maintained and in a clean work environment.

‘Magnetic’ or self-adhesive albums should never be used.

Do not roll oversize material. Store it flat in drawers or in a folder or box. I

Slides can be stored in slide boxes, albums or hanging files made of an appropriate material as for prints and negatives.

X-rays should be treated as negative sheets and stored in archival envelopes or plastic sleeves and then boxed or held in file systems.

Copying and Exhibition
For frequently used or significant material, reference copies should be made. A master and a working copy should be produced. If multiple reference copies are required a duplicating copy is also recommended. Photographic material should not be photocopied as the UV light emitted by the copier can damage the image.

Original photographic material should only be exhibited under stringent environmental guidelines. Copy material should ideally be produced for display.

Historic photos can be difficult to identify. This is a gelatin developed out print of a daguerreotype.Hand coloring, retouching, and varnishing can confuse the identification process. These additions to the original image are sometimes so subtle that consultation with a conservator may be required for positive identification.

Photographic prints can be difficult to identify; they are also difficult to treat. Photographs are extremely sensitive to moisture, solvents, and abrasion. Their cleaning or repair should be carried out by a photographic conservator or trained technician in order to guarantee sympathetic care and prevent further damage.

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Albums and Scrapbooks
Many historical collections contain albums and scrapbooks, that often pose challenging preservation concerns. Bindings can be fragile or damaged; support pages are often acidic and brittle. Scraps may include a variety of formats. For example, cards, photographs, booklets, and other ephemera might be includeded in the same volume, complicating preservation options.

When confronted with deteriorating photographs in albums or scrapbooks, you must make some critical decisions. You must evaluate the extent of damage being caused to the photographs, whether it is possible to remove and rehouse them, and whether the album or scrapbook itself has value as an artifact. If the contents are adhered to acidic pages, it may be desirable to "recreate" a scrapbook by transferring its contents to a new scrapbook of archival quality. Alternatively, photographs may be removed from an album and rehoused in permanent quality enclosures. In both cases, identifying information must be transferred.

In some cases, it may be impossible to remove photographs that have been glued down. In other cases, it may be undesirable to do so even if it is possible, for example, if the pages themselves have extensive notes or decoration that gives the scrapbook special value. Making a preservation photocopy or microfilm copy of fragile volumes should be considered for access purposes

You may decide that the album or scrapbook has artifactual value and must remain intact. In this case, the book should be housed in a box of archival quality that conforms to the size of the book. Interleaving sheets of thin Mylar or chemically stable paper may be used to keep deteriorated objects from damaging adjacent pages. No objects should be in contact with endsheets, since they tend to be acidic.

Albums and mounted material are susceptible to the same intrinsic deterioration problems of other paper-based records - brittleness, discolouration and loss of adhesion in the mounts.

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Production Standards
Different photographic materials have different levels of stability and therefore different life expectancies. When photographic methods are used as a recording system, it is important that the quality of the format is appropriate for the purposes for which the photos will ultimately be required, for example:

Polaroid prints are ideal for quick, short-term retention images but should never be used as a permanent record.

35 mm positive and negative ‘domestic’ films may be suitable as auxiliary material but are not generally classed as preservation quality. Larger format, or 'professional' quality films should be used for important images.

Film should be used well within the use-by date, otherwise image quality and colour rendition can be seriously affected.

For permanent value records, film should always be processed to Australian or international standards. Professional film laboratories should be used, rather than rapid process minilabs which do not provide archival processing.

Transparencies or slides - positive images on a transparent film base therefore requiring viewing with a back light source or projection system. The most common are 35 mm slides but other sizes are also used.

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