Acid: A substance that produces hydrogen ions when dissolved in water. Acids have a pH of less than 7.0. Acid is produced in paper when the paper and papermaking chemicals in the paper deteriorate, or when acid is absorbed from its environment. Over time, acid breaks the paper fibers down, causing the paper to deteriorate and become brown and brittle.

Acidic: A term used when something contains acid or has a pH level lower than 7.0.

Acid Free: A term describing materials with a pH value of 7.0 or higher. Note: Materials with a pH level of 7.0 are neutral and those with a pH level greater than 7.0 are alkaline.

Acid Migration: The transfer of acid from one acidic material to another less acidic material, either by direct contact or by absorption of acidic gases from the surrounding atmosphere.

Adhesive: Any substance that allows two or more surfaces to adhere to one another.

Alkaline: A term used when something contains alkali or has a pH level of more than 7.0. It is the opposite of acidic. In paper products, an alkaline substance is added to the pulp during the manufacturing process, which gives permanence
and durability.

Archival: Originally the term "archival" meant that a material or product is permanent, durable, or chemically stable and that it can therefore be used safely for preservation purposes. No standards exist that describe how long an
"archival" product will last.

Buffer: An alkaline substance-generally calcium carbonate (CaCO3)--added to the paper to make it acid free.

Buffered: A term used in the paper industry designating that an alkaline filler has been added during the paper making process, which makes the paper acid-free. It also increases the smoothness of the paper surface, improves brightness and opacity, and helps prevent ink from feathering.

Cardstock: A general term for heavier papers frequently used in scrapbooking.

Colorfast: A pigment or dye that is resistant to environmental exposure, such as light, acid, heat and other atmospheric conditions.

Cropping: Altering the boundaries of a finished photograph by trimming or masking the photo.

Deacidification: An alkaline-salt process that raises the pH level in paper. It impregnates the paper with a high alkaline reserve and neutralizes existing acids while preventing the development of future acids.

Digital: A process that uses numerical digits to create a uniform picture on a computer.

Dye: A colored substance (which is soluble) that is added to ink, paper and textiles. Generally speaking, dye colors are not permanent enough to be used for fine-art applications where long term lightfastness is required.

Emulsion: The silver-gelatin image layer of processed film.

Humidity: The measurement of the moisture content of air.

Lightfast: A term describing a material not affected or faded by sunlight, fluorescent tubes and lighbulbs.

Lignin: The substance that gives plants and trees their strength and rigidity, and also binds wood fibers together. When wood is broken down to make paper, the lignin becomes unstable. Paper that contains large amounts of lignin, such as newsprint, is very acidic and will turn yellow when exposed to light and humidity.

Lignin Free: To be considered lignin free, paper can contain a maximum of one percent lignin.

Migration: The transfer of chemicals to neighbouring materials. An acidic paper can make an item next to it acidic because the chemicals migrate.

Mylar: An uncoated, clear, polyester plastic made by Dupont. It is chemically stable and does not release harmful gases. Mylar D is used in sheet protectors and photograph sleeves, and is safe for encapsulation.

Neutral pH: The center reading of 7.0 on the pH scale of 0-14. It is neither acidic nor alkaline. For manufacturers, the acceptable pH neutral range is 6.5-7.5.

Non-bleeding: A term that describes an ink that does not spread from the original mark on the paper's surface.

Opaque: Any substance or surface that will not allow any light to pass through.

pH: A measurement of the degree of acidity and alkalinity. On a scale ranging from 0-14, pH 7.0 is neutral, above 7.0 is alkaline (or acid free) and below 7.0 is acidic. The scale is logarithmic progression, meaning 6.0 is 10 times more acidic that 7.0. pH can only be measured on water-soluble materials.
Note: The letters "pH" come from the French words for "hydrogen power".

Permanent: A term describing materials that are chemically stable. Permanent materials are not prone to deterioration. Pigment: A dry, powdery agent that possesses color. A pigment will not adhere to a surface, so a binder is required to unite the pigment to the paper. A pigment does not dissolve in liquid and does not fade when exposed to light.

Polyethylene: A flexible, chemically stable, naturally slippery plastic with little tendency to cling. It is normally manufactured without anti-block and slip agents. Polyethylene is used primarily in the manufacturing of photographic sleeves and poly bags.

Polypropylene: A clear, pliable, chemically stable plastic used in manufacturing of photographic sleeves. Polyvinyl acetate (PVA): A plastic with properties that cause photographs and documents to deteriorate and fade. Note: The pH-neutral glue called "PVA" which is commonly used for book binding and box making, is not suitable for use with photographs.

Polyvinyl chloride (PVC): An unstable plastic, generally called "vinyl" and "Naugahyde" that may exude oily plasticizers or emit corrosive and acid hydrogen-chloride gas. It is easily identified by its strong plastic odor. Do NOT use sheet protectors, binders, photo enclosures, corners or any other products made from vinyl with your photographs, negatives or memorabilia.

Preservation: The act of stabilizing an item from deterioration by using the correct methods and materials designed to maintain the conditions and longevity of the item.

Pulp: A wet slurry of fibers and water that is the basic ingredient of paper.

Red eye: The bright pink or red color that can appear in the pupils of people or animals pictured in a photo when the flash is used.

Sepia: A brownish color produced on photographs in the photographic process.

Solvent: A substance that dissolves another substance to form a solution. Water is a solvent for sugar.

Water Soluble: A substance that dissolves in water.