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Acid Free (Neutral pH) - Papers that are without acid in the pulp. Acid-free papers have a pH of 7.0. If prepared properly, papers made from any fiber can be acid-free.
Acid Migration - The transfer of acid from an acidic material to a less acidic or neutral-pH material. Occurs when neutral materials are exposed to atmospheric pollutants or when two paper materials come in contact. Acid can also migrate from adhesives, boards, endpapers, protective tissues, paper covers, acidic art supplies, and memorabilia.
Alum - An astringent crystalline substance used in rosin sizing to hold paper fibers together; responsible for introducing acid into the paper.
Antique - A printing paper with a rough finish but good printing surface, valued in book printing for its high volume characteristics.
Archival Paper - A paper with long-standing qualities, acid free, lignin free, usually with good color retention.
Buffering - The neutralizing of acids in paper by adding an alkaline substance (usually calcium carbonate or magnesium carbonate) into the paper pulp. The buffer acts as a protection from the acid in the paper or from pollution in the environment.
Caliper - The thickness of paper expressed in thousands of an inch.
Cellulose - The chief constituent of the cell walls of all plants. All plants contain tissue that, when properly processed, will yield cellulose. Cotton in its raw state contains about 91% and is the purest form of natural cellulose. Other sources for papermaking include hemp (77%), softwoods & hardwoods (57% to 65%), and kozo (66% to 77%).
Cold Pressed - A paper surface with slight texture produced by pressing the finished sheet between cold cylinders.
Cotton Linters - Fibers that adhere to cottonseed after ginning. Used as raw material to produce pulp for cotton fiber content papers.
Deckle Edge - The feathery edge which is the result of the natural run-off of wet pulp when making hand-made and mould-made paper, or the result of sheets being torn when wet. The edge is simulated in machine made papers by cutting them with a stream of water when still wet.
Dimensional Stability - The degree to which a paper will maintain its size and shape when subjected to changes in moisture content and relative humidity.
Eggshell Finish - Generally refers to a book grade of paper that has a fairly rough finish that resembles the surface of an egg.
Envelope Lining Paper - Tissue paper used to line the inside of matching stationery envelopes. Used for decorative purposes.
Felt Finish - Surface characteristics of paper formed at the wet end of a paper machine, using woven wool or synthetic felts with distinctive patterns to create a similar texture in the finish sheets.
Felt Side - The top side of the paper, usually recommended for best printing results.
Fiber - The slender, thread-like cellulose structures that cohere to form a sheet of paper.
Filler - A generic term to describe the non-oxidizing clays or minerals added to the pulp at the beater stage to improve paper density.
Finishing - The cutting, sorting, trimming and packing of paper.
Formation - The arrangement of fibers in a sheet of paper; can be seen by holding it up to a light source.
Gampi - A bast fiber from the gampi tree used in Japanese papermaking to yield a smooth, strong sheet.
Grain - Direction of fibers in a sheet of paper. Long grain describes fibers running parallel to the longest side of a sheet. short grain running parallel to the short side.
Grams per square meter - The gram weight of a hypothetical square meter of a particular type of paper, a good comparative measure because it does not vary with sheet size.
Handmade Paper - Paper made by hand using a mould (a frame covered with a flat, rigid screen or flexible screen). In both cases the mould is covered by a flat frame called a deckle, to contain the run-off of wet pulp, dipped into a vat of wet pulp, shaken to distribute the fibers evenly and drained of its excess water. The wet mat of fibers remaining in the newly formed sheet is then dried against blankets and may be hot pressed, cold pressed, or air dried.
High Alpha Cellulose - A very pure form of wood pulp which is considered to have the same longevity as cotton or other plant fibers.
Hot Pressed - A paper surface that is smooth, produced by pressing a finished sheet through hot cylinders.
Index Paper - A heavyweight stock, with a smooth finished used for products such as cards, brochures or any forms needing extra durability.
Intaglio Printing - The intaglio printing process uses a metal plate that has had the image cut into the surface. The sunken image is filled with ink and the surface is wiped clean so only ink is left in the sunken image areas. It is a very specialized process that gives a document a very high quality look. Intaglio is an old printing process but is still used today as one of the best security features on valuable documents.
Job Lot - Paper that does not meet specifications of the manufacturer or end user. For some reason it is no longer considered first quality. It may not meet standards or it may also be the overrun from an order. This paper is usable and can generally be purchased at a substantially lower cost than the first quality paper.
Jump Perforation - A partial perforation that runs parallel to the direction that the web is running through the press. Also called a skip perforation.
Kozo - The most common fiber used in Japanese papermaking, it comes from the mulberry tree. A long, tough fiber that produces strong, absorbent sheets.
Laid Papers - Papers with a “grid” pattern in the sheet, resulting from the pulp resting against wires on the papermaking mould screen. “Laid” lines are closely spaced, while “chain” lines are farther apart and run parallel with the grain direction of the sheet, important when folding papers, especially to bookbinders.
Lightfastness - The speed at which a pigment or colored paper fades in sunlight.
Lignin - A component of the cell walls of plants that occurs naturally, along with cellulose. lignin is largely responsible for the strength and rigidity of plants, but its presence in paper is believed to contribute to chemical degradation. To a large extent, lignin can be removed during manufacturing.
Linters - Short residual organic fibers that adhere to ginned cottonseed, used nowadays in place of rag in the manufacturing of paper.
Machine-made Paper - Paper made on a very rapid running machine called a “Fourdrinier,” producing consistent quantities of sheets or rolls.
Methylcellulose - A pure adhesive which dries clear. Suitable for archival mounting.
Mitsumata - A bast fiber used in Japanese papermaking that yields a soft, absorbent and lustrous quality.
Mould-made Paper - Paper made by a slowly rotating machine called a cylinder mould that simulates the hand-papermaking process. Fibers become more randomly intertwined than in machine-made papers, producing a stronger, more flexible sheet or roll.
Nap - A slight surface texture of some writing surfaces.
OCR Paper - Paper that has been manufactured to meet the requirements of the optical character requisition equipment utilized to read and record the characters printed on the paper. Properties of this stock generally include a higher level of brightness for contrast with printed characters, dimensional stability and resistance to curl. It requires stronger fiber bonding to resist picking or surface deterioration from ink. It contains low levels of surface particles and has a high level of resistance to moisture penetration.
Offset Paper - Paper that has been manufactured with properties that make the paper suitable for offset printing. Some of the properties include dimensional stability, resistance to curling, high surface strength a surface free from foreign particles and a high level of resistance to moisture penetration.
Out of Register - When an image is not printing in the exact location that it is suppose to. When printing more than one color, if the colors do not line up properly, they are out of register.
Overruns - The quantity of items produced over the quantity that was originally ordered. Also referred to as any paper spoiled in the process of printing.
Parchment - Animal skins or linings stretched and prepared as writing/painting surfaces. Produces a smooth, buttery surface.
pH - In chemistry, pH is a measure of the concentration of hydrogen ions in a solution, which is a measure of acidity or alkalinity. The pH scale runs from 0 to 14 and each number indicates a tenfold increase. Seven is pH neutral: numbers below 7 indicate increasing acidity, with 1 being the most acid. Numbers above 7 indicate increased alkalinity with 14 being the most alkaline. Paper with a pH below 5 is considered highly acidic. Buffered papers typically have a pH between 8.5 and 9.5.
Ply - A single layer of paper. A term used when several sheets of paper are laminated together to form a board.
Pulp - Any cellulose plant fiber cleaned and beaten into a wet mixture used to form sheets of paper.
PVA (Polyvinyl Acetate) - An archival white glue that is stronger than gel medium. It mixes well with gloss medium. Transparent even after many coats and remains water soluble. Mixed with gel it becomes water resistant.
Quadroplex - A term used to describe two-up printing on a duplex printer. Two pages are printed on each side of the sheet, aligned to produce four pages.
Quadtones - Four halftone images, produced at different screen angles, which were made from the same image and then printed over each other in four different colors.
Rag - Formerly the principal raw material used in the paper-making process; often meaning cotton rags. Rag content describes the amount of cotton fiber relative to the total amount of material used in the pulp. “Rag content” is not widely used today (or is a misnomer), as more and more high-quality paper is made not from rag but from linters.
Rice Paper - A common misnomer used to describe Oriental papers. There are no papers made from rice, although rice starch was traditionally used to size papers made of Kozo (mulberry plant), Gampi, or Mitsumata.
Rough - A heavily textured paper surface produced by placing wet sheets of paper against textured blankets or air drying (or both).
Size or Sizing - The process by which gelatin rosin, starch or other synthetic substance is added to paper to provide resistance to the absorption of moisture or eliminating ink feathering and bleed through. Sizing added to the beater or vat of pulp is known as internal sizing. After a sheet is formed, it may be either surface sized (painted or brushed on the surface), or tub sized (immersed in a bath).
Sulphite - Sulphite pulp is produced from the wood of coniferous trees. Wood chips are cooked in calcium bisulphate or sodium sulphite, and bleached, producing fairly long strong fibers. Since the end of the 1860s until recent years, it has been the most widely used pulp in America. In fact, the term sulphite has become generic and is still accurately used to describe any paper made from wood, as opposed to papers made from cotton or other fibers. Sulphite pulp is available in a range of grades up to pure alpha cellulose.
Tooth - A very slight surface texture of paper preferred for dry media such as charcoal and pastel.
Uncoated Paper - Paper that has been manufactured without the use of coating materials.
Unders - Underruns, the quantity of pieces that a printing run is short of the original order quantity.
Vellum - A paper surface that is finely textural. Vellum is also used to designate heavy-weight, translucent drawing or drafting papers.
Waterleaf - A paper with little or no sizing. Very absorbent.
Watermark - The translucent design or name easily visible when a sheet is held to the light. A design is sewn onto the papermaking screen with raised wire. When the sheet is formed, the pulp settles in a thinner layer over the wire design.
Web - The continuous ribbon of paper, in its full width, during any stage of its progress through the paper machine.
Wheat Paste - A preferred archival adhesive for book arts.
Wove paper - Papers which show no fine “laid” lines running through the sheet when held to the light.
Xerographic Bond - Paper suitable to use for making copies on a photocopier.
Yield - A measure of the square inches of paper per pound.
Z-fold - A paper fold represented by back and forth folds into three panels.
Zig-zag Folding - The fan-folding used on continuous forms to convert roll paper to a continuous flat stack of forms.