A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
- Acetate
- In the photographic context, a transparent plastic base for photographic film made by treating cellulose with acetic acid. This term is used for various modifications of cellulose acetate, e.g., cellulose diacetate, cellulose triacetate, cellulose acetate propionate, and cellulose acetate butyrate.
- Acetate decay
- Degradation of cellulose acetate film base that may cause distortion, shrinkage, and brittleness, often detected by a vinegar odor. The severity of decomposition can be determined using A-D Strips. (See also Vinegar syndrome)
- A-D Strips
- Indicator papers, manufactured by IPI. The strips change color when acetic acid is produced by degrading cellulose acetate film base (See Vinegar syndrome).
- Baryta
- A layer of barium sulfate in gelatin applied to the surface of photographic paper base to provide opacity, smoothness, and brightness.
- Base
- The support of an imaging or recording material on which the recording layer is coated.
- Binder
- The polymer that contains recording or imaging particles. For example, gelatin is the binder for silver image particles in photographic media.
- Binder degradation
- Decomposition of the polymer layer that contains the recording material. (See also Magnetic shedding)
- Biological decay
- Caused by the attack of biological organisms on objects and materials. Organic materials are particularly susceptible. Some examples are staining from mold growth and loss due to feeding by insects or their larvae.
- Buckling
- Distortion or lack of flatness. This may be caused by chemical degradation, shrinkage, or flow. (See Distortion.)
- Channeling
- Buckling of the emulsion caused by base shrinkage.
- Chemical decay
- A chemical reaction that causes changes in an object at the atomic and molecular level. Examples include metal corrosion, deterioration of pigments, staining by acidic materials, and embrittlement of pulp papers and textiles.
- Climate Notebook® (CNB)
- IPI’s software program for environmental monitoring and analysis.
- Color balance shift
- A change in the overall tone of color images.
- Color bleeding
- Movement of the colorant in color images, laterally into adjacent areas in the image plane, through the base (often appearing on the verso of the sheet), or outside the image plane to a contacting sheet.
- Color fading
- A decrease in image density that results in an overall lightening of the image.
- Color image decay
- Can be manifested as color fading, color balance shift, yellowing, or color bleeding.
- Composite materials
- Materials made up of two or more materials. Individual materials will react with the environment in different ways, often in opposition to each other, setting up physical stress and causing chemical interactions that cause deterioration.
- Crossed polarizers
- Polarized sheets whose axes of transmission are oriented at right angles to each other for the purpose of depicting the orientation of polyester molecules. Bands of color appear when polyester support is placed between crossed polarizers.
- Delamination
- Separation of individual layers of a laminated material, e.g., separation of emulsion from the glass base in photographic plates or separation of individual layers in optical discs.
- Dew point
- A measure of the absolute amount of water in the air. As air is circulated into and around a building, its absolute moisture content—and therefore its dew point—does not change unless it is humidified or dehumidified. Dew point is the temperature at which water will begin to condense out of the air, expressed in degrees F or C.
- DewPoint Calculator
- A program designed by IPI to illustrate the interrelation of temperature, relative humidity, and dewpoint. The DewPoint Calculator can be used to explore aspects of this relationship in a storage or display environment.
- Dimensional change metrics
- Measures of the potential for physical change in an organic material caused by gain or loss of moisture.
- EMC (Equilibrium moisture content)
- The amount of moisture in a material at a certain relative humidity. An object equilibrates as it absorbs and releases moisture in an effort to reach a balance between its moisture content and that of the surrounding environment. (See Organic materials.)
- Emulsion
- The image-forming layer of photographic films, papers, and plates.
- Fogging
- The generation of unwanted non-image density in non-reversal photographic materials or unwanted loss of image density in reversal photographic materials. This may be caused by exposure to radiation or chemicals, by aging, or by excessive or unwanted reactions during processing.
- Gelatin
- A protein obtained from naturally occurring collagen. Used as a binder for the image layer of photographic materials.
- Glass deterioration
- Degradation of glass supports caused by exposure to high humidity. May result in a hazy appearance, formation of liquid droplets, or layer separation in photographic glass plates.
- Harmful enclosure
- A folder, envelope, sleeve, box, or other container that causes silver image decay and/or staining of binder and supports.
- I3A
- The International Imaging Industry Association, which facilitates the development of media storage and other technical standards for the imaging industry.
- Inorganic materials
- Materials with a geological origin, which have undergone extreme pressure or heat, usually are not combustible at normal temperature, can react with the environment to change their chemical structure (corrosion or dissolution), and usually are not sensitive to light.
- ISO
- The International Organization for Standardization, in Geneva, Switzerland, which publishes international specifications, test methods, and best practices for a variety of industrial products and processes.
- Layer separation
- The partial or complete separation of a laminate into its constituent layers. (See also Delamination.)
- Life expectancy (LE)
- A rating for the expected longevity of recording materials and associated retrieval systems.
- Magnetic shedding
- Degradation of the binder of magnetic tape, which results in loss of magnetic oxide particles during storage or playback.
- Mechanical decay
- A change in the physical structure of an object caused by changes in the environment (variation in and improper levels of temperature and relative humidity) that lead to stresses in an object. Examples include cracking and buckling of wood; warping, shattering, and cracking; and softening of plastics and waxes. Mechanical decay is also caused by force resulting in chipping, cracking, abrasion, distortion, etc.
- Microspots
- Small colored spots, usually red or orange, caused by localized oxidation of black-and-white images. Also known as red spots, redox blemishes, or measles.
- Mold
- Fungus that grows on polymer or organic materials exposed to high humidity; causes material degradation.
- Mold risk factor (MRF)
- A number derived from temperature and relative humidity data over a period of time which expresses the likelihood and severity of mold growth on susceptible collection materials.
- Molecular sieve
- A material containing tiny pores of a precise and uniform size that is used as an adsorbent for gases and liquids.
- Nitrate
- In the photographic context, a transparent plastic base that was used for photographic film until 1949 in the USA. Obtained from the treatment of cellulose with nitric acid.
- Nitrate decay
- Degradation of cellulose nitrate film base that may cause yellowing, buckling, film distortion, and corrosion of metal cans. Can also cause gelatin binder to become soft or sticky or to disintegrate.
- Organic materials
- Derived from once-living things, i.e., plants or animals. These materials contain carbon, are combustible, and are susceptible to deterioration from extremes and changes in relative humidity and temperature. They absorb moisture from their surroundings (i.e., are hygroscopic) and release moisture to the surrounding air in order to reach equilibrium. They are sensitive to light and are a source of food for mold, insects, and vermin.
- Outgassing
- The tendency of some materials, e.g., acetate and nitrate film bases, to give off vapors as they decay. Some of these vapors may be harmful.
- PAT (Photographic activity test)
- Evaluates chemical or photographic interactions between enclosure materials
and photographic images, as described in ISO 18916.
- PEM (Preservation Environment Monitor)
- A unique electronic datalogger created by IPI for monitoring storage environments in cultural institutions. The PEM collects and stores temperature and humidity data along with two specially calculated indices—the preservation index (PI) and the time-weighted preservation index (TWPI)—that are used to measure the natural aging of organic materials.
- PI (Preservation index)
- A means of expressing how ambient temperature and RH affect the chemical decay rate of collections. PI illustrates, in years, how long it will take for vulnerable organic materials such as poor-quality paper to become noticeably deteriorated under current (and unchanging) environmental conditions. PI is not a predictor of the useful life of any object or collection but is a convenient comparative measure, using short-lived materials as a yardstick.
- Polarizer
- A sheet, containing oriented particles, that transmits light that vibrates in only one direction.
- Polyester
- A transparent plastic base for photographic film and magnetic tape that is composed of a polymer of ethylene glycol and terephthalic (or naphthalene dicarboxylic) acid. It is very strong and stable.
- RC
- An acronym for “resin-coated.” A polyethylene film applied to both sides of photographic paper base for the purpose of speeding processing and drying.
- RH (Relative humidity)
- The amount of water vapor in the air expressed as a percentage of the maximum amount that the air could hold at the given temperature.
- Sheet film
- A single piece of flat (non-roll) film found in various formats, such as 4” x 5” or 5” x 7”.
- Silver image decay
- A defect of a black-and-white silver image, which can be manifested as microspots, silver mirroring, or overall image discoloration.
- Silver mirroring
- Oxidation of black-and-white images, in which the image silver migrates to the surface, creating a mirror-like appearance.
- Support
- The glass, plastic, or paper base on which the image layers of photographic film, prints, or magnetic tape are coated.
- System obsolescence
- A problem associated with machine-readable images, data, or sound recordings, whereby the information can be recovered only by using hardware or software that is obsolete.
- Tape deformation
- Distortion of magnetic tape resulting in lack of flatness. (See also Buckling.)
- Thermal equilibration
- The process by which the temperature of an object becomes the same as that of its environment, or the state of having the same temperature as that of the environment.
- TWPI (Time-weighted preservation index)
- Adds the element of time and the cumulative effect of deterioration to the PI to give a more realistic estimate of the long-term effect of an environment on preservation. TWPI illustrates the effects of fluctuating conditions, over a whole period of time, as a single value. It is the harmonic mean of the PIs: a more correct way of averaging PI than the arithmetic mean ordinarily used.
- Vinegar syndrome
- This slow form of chemical deterioration of cellulose acetate film is caused by poor storage conditions. It is so named because, as film degrades, it gradually shrinks, becomes brittle, and generates acetic acid, which evaporates into the air, producing a sharp, vinegar odor.
- Yellowing
- Discoloration that affects a color image or, in earlier color processes, the white border of a print.
