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SECTION 2: Archival Storage of Photographic Materials

Introduction

Selecting Storage Materials

Standards for Materials

Preparing Collections

The Storage Environment

Case Studies


 

Introduction

Photographs are found throughout our museums, libraries, historical societies, archives, and homes. Often taken for granted, photographs are actually fragile and easily damaged. Fading, stains, distortion, and other physical changes are signs of their deterioration. Unfortunately, deterioration is often the result of the inherent instability of certain photographic processes and materials—cellulose acetate negatives, nitrate negatives, and color slides and prints, for example. While the nature of our collections may be outside our control, deterioration can also be initiated or hastened by poor storage conditions and display techniques, which are our responsibility. The goal of this section is to provide the preliminary background information necessary to select appropriate storage materials for photographic collections. People with small personal collections may find this pamphlet adequate for their needs. Professional photographers, curators, archivists, and dealers will need to read further if they are to develop appropriate preservation programs. Fortunately, a number of excellent books are now available.

No amount of reading, however, can provide all the answers if your collections are extensive, in poor condition, or include valuable works of art and rare examples of early photographic processes. Professional photographic conservators have the technical expertise to assess the condition of photographs and make recommendations for their storage and treatment. The American Institute for Conservation (conservation-us.org) can provide the names of conservators in your region as part of their referral service.

This section reflects our current understanding of the storage requirements of photographs. It will be revised as new information and products become available. Unless noted otherwise, the items mentioned in this section are available from Gaylord Archival. Click here to request a free Archival Catalog.


 

Selecting Materials

Storing your collection in appropriate envelopes, sleeves, albums, and boxes is fundamental to their preservation. These enclosures make photographs last longer because they protect against light, dust, handling, air pollutants, and rapid fluctuations in temperature and humidity. They must be made of materials that are strong, durable, and chemically stable if they are to provide long-term protection.

Suitable materials for the storage of photographs and negatives are now available, but buyers should use judgment and select a supplier who specializes in products for archival use. Suppliers' claims of "archival quality" in their catalogs and advertisements should be substantiated by product descriptions and test results that provide adequate technical information. Materials that come in contact with photographs should pass the Photographic Activity Test (PAT), ISO 18916, an accelerated aging test that verifies that they are non-damaging to sensitive photographic materials.

Paper—Since poor quality folders and envelopes can hasten the deterioration of photographs and negatives, it is essential that paper be free of acidic compounds such as those found in alum-rosin sizing and unpurified wood pulp. It is also important that the paper and boards used to store photographs have very low levels of lignin (less than 1%) because lignin can cause staining and fading.

Acidity and alkalinity are measured by pH, using a logarithmic scale of 0–14, where 7 is neutral. Paper should not have a pH below 7. In most cases, choose a paper that has a pH of 7.5 to 9 and an alkaline reserve of 2-3% calcium carbonate, which will neutralize acid contaminants that come in contact with the paper. Some photographic processes, however, will react to alkaline environments. For these materials, unbuffered paper with pH 7.0 to 8.5 is best for envelopes and folders.

In summary:

All papers used to store photographs should pass the Photographic Activity Test. Nitrate and cellulose acetate film should be stored in buffered paper. Unbuffered paper should be used for cyanotypes, including architectural blueprints and dye transfer prints. The current ANSI Standard recommends unbuffered paper for color photographs and color negatives; buffered paper for black and white photographs and negatives.

Paper has advantages for storing photographic materials. Its opacity protects images from light and provides a surface for written information. Its porosity prevents the accumulation of moisture or harmful gases. However, items must be removed from paper enclosures to be seen, increasing the chance of mishandling and abrasion.

Paper Enclosures—Enclosures should protect items from dust and handling, and provide physical support. Envelopes should be sealed on the edge with an inert adhesive. Adhesive-free paper enclosures, including folders and four-flap enclosures, are available.

Glassine—Although it has been the traditional material for storing negatives and for interleaving, glassine is no longer recommended for use with photographic materials. Buffering causes glassine to lose its translucency, and the thin unbuffered paper quickly absorbs environmental acids and moisture.

Interleaving Paper—A soft, smooth paper can be used to interleave photographic prints that are not placed in individual sleeves and to protect the surface of matted prints. Interleaving paper provides a barrier against dust and abrasion during storage and use.

Board—Like paper, board can be manufactured to be free of acids. The board used for most archival storage boxes is 60 points (60mil) thick or 40 points thick. Any board used should pass the Photo Activity Test.

Storage boxes made of barrier board should be sturdy enough to support their contents and have reinforced corners. Snug lids will prevent dust and pollutants from entering. Boxes are available in a range of styles, which are illustrated in the Case Studies at the end of this section.

Mat Board—When matting and framing photographs, use conservation board of cotton fiber or purified wood pulp. These boards are available in two-, four- and eight-ply thicknesses. The heavier weights are recommended for oversized photographs that need extra support.

Plastic—Clear plastic enclosures are particularly useful for photographs and negatives that receive continual handling and viewing. Plastics must be chemically stable, free of additives and abrasive surface coatings.

Plastics manufactured for commercial packaging, for example, often contain additives that react with oxygen and light to produce harmful chemical compounds that can damage photographic materials. Unfortunately, it is difficult to distinguish plastics with additives or surface coatings by look or touch. The best guarantee of quality is to purchase enclosures from a recognized supplier of archival materials.

Three types of plastics are currently considered acceptable for long-term storage:

  1. Polyester—Archival polyester (often referred to by brand names Melinex® and Mylar®) is a brand of polyester that meets the requirements of long-term storage of photographic materials. Clear, smooth, and rigid, polyester gives support while letting users see the image.
  2. Polypropylene—Untreated (uncoated) polypropylene is an acceptable low cost alternative to polyester. It is less rigid but is clear, and can be used for photographic materials that do not need the greater support provided by polyester; or where the greater cost of polyester cannot be justified. Avoid polypropylene that has a surface coating applied.
  3. Polyethylene—The softest of the plastics and the least clear. High-density polyethylene is translucent, like glassine, and its smooth surface is the least likely to cause surface abrasion. Like polypropylene, it is a lower cost alternative to polyester, where the clarity and rigidity of polyester is not needed.

Vinyl pages and some "magnetic photo albums" are unacceptable for the storage of photographs. Sheets and enclosures made of polyvinyl chloride (also called PVC or vinyl) are recognizable by their oily feel and smell. They release chemicals that react with photographic materials to cause staining and deterioration. Many older style "magnetic albums" have poor quality backing pages coated with a tacky adhesive that may cause discoloration and make it difficult to remove photographs in the future. Cellulose triacetate is not recommended for long-term storage because it becomes distorted and can cause surface abrasion.

Plastic Enclosures—Several types of enclosures, made from the three safe plastics, are available. Unlike paper, plastic allows users to view the image without removing it. Ultrasonic or heat-sealed seams eliminate problems from adhesives, and the plastic protects the image from moisture and pollutants. Some of the most common enclosure types are folders, envelopes, sleeves, and storage pages for three-ring binders.


 

Standards & Testing

The American National Standards Institute (ANSI) and the International Organization for Standardization (ISO) have developed technical standards for photographic materials, processing, and storage. These include:

  1. American Standards for Imaging Materials—Processed Photographic Films, Plates, and Papers—Filing Enclosures and Storage Containers, ISO 18902, (ISO old number 10214), ANSI/NAPM IT9.2
  2. American National Standard for Imaging Materials—Processed Safety Photographic Films—Storage Practices, ISO 18911, (ISO old number 5466), ANSI/ NAPM IT9.11
  3. American Standards for Imaging Materials—Processed Photographic Materials—Photographic Activity Test, ISO 18916, (ISO old number 14523), ANSI/NAPM IT9.16
  4. American Standards for Imaging Materials—Polyester Base Magnetic Tape—Storage Practice, ISO 18923, (ISO old number 15524), ANSI/NAPM IT9.23
  5. American Standards for Imaging Materials—Optical Disk Media— Storage ISO 18925, (ISO old number 16111), ANSI/NAPMIT9.25

Adherence to standards rests with the supplier. Gaylord's archival products are manufactured to the most current standards established by ANSI and ISO, and to the specifications of institutions such as the National Archives and Records Administration and the Library of Congress Preservation Directorate. Information and specifications about their products are available from Gaylord.

For quality assurance, Gaylord maintains an independent testing program. Samples of photographic storage materials are periodically sent to the Image Permanence Institute in Rochester, New York, where the Photographic Activity Test is administered. Tested materials include box board, album pages, envelopes, and folders. Results are available on request.


 

Preparing Collections

Before selecting storage materials, you will want to evaluate your collection from several points of view. For the family collection, this may be as simple as sorting photographs on the dining room table. For the large institution, a survey may be required.

  1. Assess the value of your collection. Are the photographs unique? Do negatives exist to make duplicates? Are the prints valuable as works of art or as historical documents? These answers will help set priorities and budgets.
  2. List the types of formats, sizes, and quantities of items in your collection so that you can select appropriate types and amounts of storage materials.
  3. Anticipate the use the collection will receive. Who will use the photographs? How often? Heavily used collections will need extra protection, especially if materials are to be handled without supervision.
  4. Obtain copies of unique or important images. Good quality copy prints are useful for display, for added security, and for sharing with others. Larger portrait studios and photography shops can provide copy services for reasonable rates.

Follow these guidelines as you prepare your collection for storage:

  1. Handle prints and negatives along the edges, preferably wearing white cotton gloves. Dirt, dust, and oils from your fingers can cause permanent damage.
  2. Remove photographs and negatives from poor quality enclosures if it is possible to do so without causing damage. Remember to keep all information from the old pages. If prints are dry mounted or glued to old album pages and mats, do not attempt to do the work yourself. Place the entire page in a folder or plastic sleeve.
  3. Remove extraneous materials such as paper clips, rubber bands, old clippings, and notes. If important, these can be placed in envelopes and stored separately. Newspaper clippings should be photocopied onto alkaline paper.
  4. Note any badly damaged items, place them within individual folders, and set them aside for professional conservation treatment. Do not undertake any "first aid," and never use pressure-sensitive tapes or glues to mend photographs. It is far better to make a copy print and store the damaged original.
  5. Whenever possible, place identifying information on the enclosures rather than on the photographs themselves. Use a No. 2 pencil, Pigma pen, or India ink on paper, and a film-marking pen on plastic. Felt tipped pens and ball point pens should never be used because the ink can "bleed through" and stain the photograph. Use labels with a stable adhesive on boxes and folders.
  6. If it is necessary to have identification on the photograph itself, write brief notations lightly on the back with a lead pencil (No. 2 or softer). If the surface of resin coated paper does not accept pencil, use a blue photo marking pencil or a film marking pen to write on the back edge of the print.

 

The Storage Environment

Once photographs have been placed in enclosures, they should be stored in an environment that is dark, cool, and dry. Research has proven that high humidity and temperatures will accelerate deterioration in films and prints. Silver images (black and white photographs) are affected primarily by humidity and contaminants from poor quality enclosures or air pollution. Color photographs are sensitive to light, heat, and humidity. Light is such a threat to color prints that it is best to have a second copy (kept in the dark) of any color prints that are displayed for long periods. Prolonged damp conditions (relative humidity over 65%) can lead to mold growth on photographs. Fluctuations in temperature and humidity may cause yellowing or staining to digital prints, as well as color bleeding. Ozone and other pollutants may cause image deterioration, particularly with dye images on micoporous coating. Protect optical disks from scratches, abrasions, dust, and pollutants. Corrosion of the metallic surface and mold growth may occur on disks due to high humidity.

Achieving an acceptable environment is critical if photographs are to survive. For families, this means removing photographs from damp basements and overheated attics. A shelf in a dark closet on the main floor is often the best location available in a home. When storage conditions are less than ideal, it becomes even more important to provide enclosures and boxes that buffer the photographs from the deleterious effects of the environment.

Institutions must ensure more extensive environmental controls. The International Standard Organization provides up-to-date information concerning the care and handling of photographs. Since photographs, including negatives, are made with various materials, it is difficult to provide uniform storage recommendations for all formats. The Image Permanence Institute has created a Storage Guide for Acetate Film (SGAF), based on the recommendations from the International Standard Organization. This guide provides the ISO standards and also includes a simplified version to assist in the long-term preservation. For the simplified version, reference to cool and cold for this context can be translated as: 54°F (12°C) and 40°F (4°C), respectively.

Photographic film: black-and-white and color
Maximum temperature depends on maximum RH.
Simplified: cold with maximum 50% RH.

Black-and-white prints
Maximum temperature 64°F (18°C), for maximum 50% RH. Simplified: cool with maximum 50% RH.

Color prints
Maximum temperature depends on maximum RH.
27°F (-3°C) maximum temperature for maximum 50% RH.
36°F (2°C) maximum temperature for maximum 40% RH. Simplified: cold with maximum 50% RH.

Digital Output
ISO has not yet established storage recommendations specific to inkjet prints. Until it does, the conditions specified for color photographic prints apply to ink jet.

Optical disks
70°F (21°C) for maximum 50% RH

Simplified: cool and cold considered optimum. Frozen not recommended because of concerns about layer separation.

Institutions with substantial collections of photographic negatives and prints will want to segregate these materials to provide optimum conditions for long-term preservation. Institutions that cannot store photo-graphs, documents, manuscripts, and books separately will need to com-promise.

Control of contaminants and pollutants is also recommended. This involves effective air circulation and filtration to remove gaseous pollutants and particulate matter from incoming air. For more information about environmental issues, consult Conservation Environment Guidelines for Libraries and Archives, the IPI Storage Guide for Acetate Film, IPI Media Storage Quick Reference, andThe Permanence and Care of Color Photographs. The last citation includes detailed information about cold storage of archival collections of color prints and negatives.


 

Case Studies

Selecting specific envelopes, albums, and boxes requires careful consideration. Physical condition, size of collection, anticipated use, and budget all play a part in developing a strategy. Section 2 presents several case studies to show how the products available from Gaylord can be used to store photographic prints and negatives. If the photographs are part of a larger archival collection, consult Section 1: Archival Storage of Paper for additional information.

CASE STUDY I: PHOTOGRAPHS—UNMOUNTED

Scope: Standard Size Unmounted Photographic Prints, (black & white and color) (See Case Study III for details about storing mounted photographs).

A. Select appropriate primary enclosures made of chemically stable and durable materials that will protect the photographs and not cause damage. All storage materials should pass the Photo Activity Test. Unless the prints have little value or are consulted infrequently, it is best to place each print into an individual enclosure.

  1. Photographs that are viewed often may be placed in plastic enclosures that allow the image to be readily seen. Because of its rigidity, polyester provides better support for prints that are fragile or on thin paper. However, it should be avoided for prints with flaking emulsion that could be lifted by static electricity. Very fragile prints may need the additional support of acid-free board.
  2. Photographs may be placed directly into paper enclosures. If this option is selected, the paper should be pH neutral and unbuffered for color prints, alkaline/buffered for black and white prints. Enclosures come in a range of styles. Avoid envelopes with center seams and select those with seams along the bottom and side, sealed with a stable adhesive.
  3. If the photographs are going to be boxed without enclosures, place interleaving paper between the prints.

B. Place sleeves or envelopes in folders or boxes that are made of paper or board that is acid-free, has a low lignin content, and passes the Photographic Activity Test. It is best to group photographs of similar sizes together in standard sized enclosures so that they provide even support for each other.

  1. Storage boxes should be strong, have reinforced corners, and match the size of the prints. A range of styles is available, depending upon the size and condition of the prints. For digital prints, to avoid pressure in a stack situation, place only a few prints in archival boxes or folders.
  2. Acid-free hanging folders may be used for active collections that are consulted frequently. Because they do not provide the additional protection against light and the environment that boxing does, hanging folders are not recommended for long-term archival storage.
  3. Prints stored in plastic sheet protectors can also be placed in 3-ring binders. See Case Study II for details. As with hanging files, binders do not provide the protection of boxes and should not be used for fragile or rare prints.

CASE STUDY II: PHOTOGRAPHS IN ALBUMS

Scope: Standard and custom size unmounted photographic prints (black and white, color, digital).

Albums are the traditional format for organizing and preserving personal collections of photographs and memorabilia. Unfortunately, the papers and glues used in the past were usually acidic. Many "magnetic albums" have adhesives on poor quality backing pages that may cause prints to discolor and stick. Today, it is possible to purchase albums that will preserve your photographs for generations to come. Gaylord offers a range of options.

A. Select an appropriately sized album made of chemically stable, durable materials. Do not use any damaging glues or tapes to attach materials to the pages.

  1. If your photographs are standard sizes, the most cost effective method is to place the prints in polypropylene sheets with pockets that correspond to print size.
  2. If you like a traditional look, select an album with paper sheets and polyester protectors. The paper should be pH neutral and thick enough to support the weight of the photographs.
  3. B. If you have an older album that you want to preserve intact because the prints cannot be removed without damage or because you don't want to lose the annotations or the original appearance, the best alternative is to place it in an alkaline/buffered box and store it flat. A box will protect the album from light and dust, and lessen the effects of pollution and handling.

    1. If photographs face each other or if the album includes unstable material like newsprint, place interleaving sheets between the pages as a barrier. Buffered interleaving papers are available. Interleaving does, however, add bulk and should not be used if it strains the binding.
    2. If the album is not used often and funding is limited, an inexpensive solution is to wrap it in alkaline/buffered paper and store it flat.
    3. If the album size corresponds to a standard size document storage box, place it in a clamshell or drop-front box so that the album can be removed without damage.
    4. Boxes should fit properly. If a pre-made box is not available in an appropriate size, consider contacting a bookbinder who can make one. Be sure to specify that all materials, especially the inner box linings, are alkaline and buffered. This is an expensive option, usually reserved for rare and valuable albums.

    CASE STUDY III: MOUNTED AND MATTED PHOTOGRAPHS

    Scope: Photographic prints mounted on board and unframed photographic prints in window mats.

    Many libraries have collections of photographs that were glued to cardboard for display, study, and teaching. Albumen prints and other types of nineteenth century photographs were also mounted. Today these acidic mounts are often brittle and cracked along the edges but cannot be removed from their mounts without seriously damaging the prints. It is necessary, therefore, to store the prints in such a manner as to prevent any further deterioration.

    At the same time, photographers continue to choose drymounting as the display technique for their work. Conservators do not recommend drymounting original art because the process is irreversible, even when museum quality board and heat-activated acrylic adhesives are used. However, collectors and museums still acquire prints that have been drymounted and need to store these prints safely.

    Matting and framing are the preferred methods for displaying and storing valuable photographs. Prints are attached to an acid-free conservation board via a reversible hinge and then covered with a window mat custom cut to display the photograph or print. Detailed descriptions of appropriate matting and framing techniques appear in The Life of a Photograph and The Permanence and Care of Color Photographs.

    Section A and Section B.1 address the storage of permanently mounted photographic prints. Section B.2 discusses proper storage of matted prints.

    A. Select appropriate materials to protect the surface of the prints and provide adequate physical support for the mounts.

    1. If the mounted prints are consulted frequently, place them in polyester sleeves. If the mounts are sound and sturdy, you may use a lighter weight plastic like polypropylene sleeves or polyethylene thumb-cut envelopes.
    2. If the board is acidic and breaking, place the mount in a 4mil Melinex® envelope with a piece of low-lignin board, slightly larger than the mount, behind it for support.
    3. If the mounted photographs are not used often or are not worth investing in sleeves, place interleaving paper over the surface of each print before boxing.

    B. Store mounted and matted photographs flat in acid-free boxes.

    1. Place mounted photographs in boxes that closely fit the size of the mounts.
    2. Matted photographs require sturdy boxes that can support the extra weight of the mat board. Their inner depth should be only 11/2 to 2 inches, to keep the weight manageable.

    CASE STUDY IV: OTHER FORMATS

    Scope: Cartes de Visite, Cabinet Cards and Stereo Cards.

    During the second half of the nineteenth century, professional photographers produced a range of mounted photographs in smaller formats for the general public. Gaylord has developed polyester sleeves and boxes to fit the sizes of the most popular formats: Cartes de Visite, Cabinet Cards, and Stereo Cards. It is best to place these items in enclosures that are specially made to size rather than to put them in oversized enclosures where they may shift or fall out, causing abrasion and damage. For more details about the chemistry and preservation of these historical materials, consult Care and Identification of 19th-Century Photographic Prints.

    A. Place mounted photographs in polyester sleeves to protect the image surface. Use self-locking polyester sleeves for Cartes de Visite and Cabinet Cards; polyester sleeves with the two long sides sealed for Stereoscopic Cards.

    B. Place sleeved cards in boxes made of low lignin alkaline buffered tan board. Use Deep Lid Storage Box for Cartes de Visite, Flip-Top and Shallow-Lid Storage Boxes for Cabinet Cards. Stereo Boxes have a slant-back design that makes it easier to view the stereoscopic images.

    CASE STUDY V: NEGATIVES

    Scope: Film Negatives, (Black & White and Color) and Glass Plate Negatives.

    Glassplate negatives were popular from 1855 until the 1920s, and flexible plastic films were introduced around 1890. Nearly all films manufactured before the 1930s—and some made as late as 1950—have a highly flammable base of cellulose nitrate. Any film marked "Safety Film" is not nitrate and is non-flammable; it has a base made of cellulose acetate or polyester plastic. Most safety films (both color and black & white) have an acetate base, although the use of polyester has been increasing since the 1960s. Currently, polyester is used primarily for large-format negatives (4 x 5 inches, etc.), while 35mm and 120mm roll film are usually on an acetate base.

    An important issue for film preservation is the inherent chemical stability of the plastic base. Nitrate and acetate are prone to decompose, release odors, and become crinkled, sticky, and generally unusable. When stored in warm, (or worse, warm and humid) conditions, the plastic base will deteriorate rapidly. In comparison, polyester film base is much more stable.

    Because of their instability, nitrate and cellulose acetate should be placed in alkaline buffered paper envelopes and sleeves for long-term archival storage. Plastic enclosures can prevent the byproducts of decomposition from escaping and cause these films to deteriorate more rapidly. If negatives show signs of deterioration, they should be duplicated onto stable polyester film. Cold storage with low or moderate relative humidity is recommended for the long-term storage of original cellulose acetate and cellulose nitrate negatives to retard further deterioration. It is especially important that cellulose nitrate be stored in a controlled environment with adequate ventilation because of the film's instability and flammability. Cold storage is also recommended for color film.

    See the IPI Storage Guide for Acetate Film, Ritzenthaler's Administration of Photographic Collections, and Wilhelm's Permanence and Care of Color Photographs or details.

    A. Select paper enclosures that match the size of your negatives. Strips of 35mm and 120mm film are placed in sleeves and larger format negatives are placed in individual envelopes. Both are available in buffered and unbuffered paper. Four-Flap Negative Enclosures eliminate all adhesives, and the flaps pro-vide additional support for prints.

    B. Plastic enclosures come in a wide range of styles and materials. They are particularly useful for collections that are used frequently because the images may be viewed without removing the negatives.

    C. Plastic enclosures can be inserted into paper envelopes. This allows you to record cataloging information on the paper envelope.

    D. Once in enclosures, negatives may be placed in boxes, binders, or hanging folders.

    E. Glassplate negatives are extremely vulnerable to damage and require additional support. Use Four-Flap Enclosures that are double-creased. Store vertically in sturdy Shallow Lid Storage Box sized to fit.

    CASE STUDY VI: DIGITAL OUTPUT

    Scope: Digital Photographs.

    Digital output is rapidly increasing as manufacturers consistently develop a variety of printing processes to generate graphic documentation, such as: office documents, books, posters, and both amateur and professional photographs, to name a few. The processes can range from: Fuji Pictography, Dye Diffusion Thermal Transfer, Liquid Ink Jet, Solid Ink Jet, Electrostatic, Direct Thermal, and Direct Thermal Transfer, to Dot Matrix. Generally, the color for digital output is made up of dyes or pigmented inks (the latter being the most stable). The paper support may be a plain (uncoated) paper, or have a swellable polymer coating (which protects the image from the environment), or a microporous coating (which has a faster drying time). There are many types of papers, inks, and dyes that are now accessible for the growing market. Because the products are continually changing, it is difficult to establish recommendations and standards. Previously, the standards for testing traditional material have been applied to evaluate digital output, but they do not address all problems related to this current technology. For instance, some digital prints are very sensitive to humidity, wetting, handling, and ozone. The ISO committee is aware of the need for appropriate test methods and is working on various issues, such as humidity-fastness, water-fastness, finger prints, indoor lighting, outdoor conditions, dark stability, and gas fading.

    For storage, in general, follow black and white photographic practices as described in this section. Gaylord has several products specifically designed for storage of digital prints. For primary enclosures, Presentation Pockets are available in 3mil and 8mil polypropylene. Melinex L-sleeves will hold large format digital prints. Digital Print Boxes are available in black or tan and have a drop-front design for easy removal of prints.

    CASE STUDY VII: OPTICAL DISKS

    Scope: CD-Rs (Photo CDs), CD-RWs, DVDs.

    There are various formats of optical disks, the most popular is the compact disk (CD) and the digital versatile disk (DVD). Optical disks can be divided into two categories. One type—audio compact disk (CD-A), DVD-ROMs and CD-ROMs (Read Only Memory), which are stamped from molds— is used for the publishing media and intended for mass production. The other type consists of writable disks on which the user can record individual data. There are two types of writable disks: those that cannot be modified after recording (CD-R, DVD-R) and rewritable disks (CD-RW), which can be modified after initial recording.

    The structure of optical disks consists of complex layers. Disks are generally composed of three layers: a transparent polycarbonate plastic wafer, a reflective aluminum or gold layer, and a protective coating. Both record-able CDs (CD-Rs), and magneto-optical (MO) disks include an additional laser-sensitive coating. The even more complex structure of DVDs is made of two CDs bonded together.

    Improper handling may cause rapid deterioration of CD's. Scratches can interfere with reading, particularly if they are around the circumference of the disk. During storage, environmental conditions play a considerable role in the media longevity.

    Because of the internal stresses which are caused during the fabrication of optical disks, rapid environmental changes can cause similar effects, such as cracks, and delamination of the layers. To date, no stability studies have yet been published on the more complex structure of DVDs. ISO standard 18925 specifies storage conditions for optical disks. These include avoiding temperature and relative humidity extremes and maintaining stable temperature and RH conditions. As with traditional materials, storing these disks in a dry, cool environment slows the degradation mechanisms. Pollutants may cause corrosion of the metallic reflective surface. The longevity of the CD-R depends on the CD itself (type of dye, metal layer, etc.) but also on the quality of the recording, which may differ from one CD burner to another. At least once every five years, the collection should be inspected for physical appearance and legibility.

    A. CDs and DVDs can be stored in polypropylene album pages for a safe, visible, and organized storage. CD Preservers are designed to hold photo CDs with their contact sheets in a standard 3-ring binder or album.

    B. Place optical disks in individual Tyvek® sleeves. These inert, non-abrasive, anti-static Tyvek® CD holders are also mold and tear resistant. Polypropylene CD Sleeves have a soft, black non-woven polypropylene interior and can hold 2 CDs.

    C. Never write on optical disks or stick labels on the surface. Instead use foil-back labels to identify sleeve contents.

    D. Optical disks may also be stored in translucent, polypropylene cases. Insert literature or labels inside case for quick identification.

    E. Always store optical disks vertically. Place sleeved or cased disks in boxes to protect them from dust and dirt. Use either a flip-top or a shallow lid for easy access. A CD Portfolio Box has a handsome black buckram exterior and will hold 100 CDs in sleeves or 80 CDs in matching CD Bins.