August 12, 2010

Paper Glossary- more, from Legion Papers

Filed under: Uncategorized — admin @ 2:49 pm

Not to be outdone by Ron Martinson and his awesome glossary of printing terms, we dug up the Legion Paper pdf from their site and double-checked to see that there was nothing missing.  We have a few notable, and some not-so-notable (read: extremely paper-geeky) additions.

Here you go, this excerpt, courtesy of our friends at Legion:

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.

Calcium Carbonate -An alkaline chemical used as a buffering in papers and boards.

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 and hardwoods (57% to 65%), and kozo (66% to 77%.)

Chain Lines -The lines visible on laid paper, parallel with the grain direction, usually about one inch apart.

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 fibre content papers.

Cylinder Machine -A papermaking machine in which a wire covered cylinder rotates partly submerged in a vat containing dilute paper stock. The sheet is formed on the outside of the wire as the water drains throughout. The paper is lifted from the wire by an endless felt. Also referred to as a mould machine or cylinder mould machine. “Mouldmade” paper is made on a cylinder machine.

Dimensional Stability -The degree to which a paper will maintain its size and shape when subjected to changes in moisture content and relative humidity. Very important in maintaining registration in printing.

Dye -Colored soluable substance that imparts a more or less permanent color to another material by staining or by chemical reaction with substrate.

FeltSide -The top side of the paper and side usually recommended for best printing results.

Formation -The arrangement of fibers in a sheet of paper, which can be seen by holding a sheet of paper to a light source. The formation of the sheet is determined by composition of the fibers, fiber length, machine speed and shake, amount of filler and other factors. Formation can run from “tight” or “close” to “wild” and is a major factor in determining how the sheet will perform, affecting factors like levelness, strength and dimensional stability.

Handmade Paper -Paper made by hand using a mould-a frame which is covered with a flat rigid screen (Western) or flexible screen (Oriental). 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 is the newly formed sheet, which is then dried against blankets & 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.

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 manufacture.of Terms Continued

Pulp -Any cellulose plant fiber (cotton, linen, wood, Japanese plants) cleaned and beaten into a wet mixture used to form sheets of paper.

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 ten-fold increase. Seven is pH neutral: numbers below 7 indi­cate increasing acidity, with 1 being most acid. Numbers above 7 indicate increasing 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.

Porosity -The porosity is an indication of the openness of the paper, as measured by resistance to the passage of air through the sheet. Two types of instruments are gener­ally used to measure porosity-Gurley and Sheffield. The Gurley instrument measures the seconds required for a given volume of air to pass through a single sheet and is generally used for porous papers. A high reading indicates a less porous (or more dense) paper. Sheffield porosity measures the flow rate of air through a single sheet and is generally used for non-porous or dense sheets. A high Sheffield reading indicates a more open paper. A typical Gurley porosity test for 50 lb. smooth offset would be 10-20 seconds. Sheffield readings of 60 lb. coated paper would be 10-20 units of air flow.

Recycled Paper -Paper made from pre and post consumer waste. Used paper is cooked in chemicals, de-inked and reduced back to pulp, which is then used to manufacture new paper.

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)

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 1860’s, 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 in distinction from papers made from cotton or other fibers. Sulphite pulp is available in a range of grades up to pure alpha cellulose.

Tear -The test is valuable to the papermaker in determining the uniformity of refin­ing the length of formation of fibers. Tear strength can be important to the printer or converter, especially when bags, maps, children’s books, etc., are involved. Determines average force in grams required to tear a single sheet after the tear has started. An Elmendorf tearing tester, employing a falling pendulum, is used with the test made in both machine and cross directions.

Tensile Strength -A test more important to the mill and pressure sensitive label converters than to the printer. Tensile strength is related to burst and tearing strength, and the combination of the two tests is often used as an indication of the inherent tensile strength. Some degree of stretch is usually desirable in paper and reflects a certain degree of elasticity which tends to minimize breaks and ruptures. (This stretch should not be confused with the stretch and shrink normally resulting from a change in moisture content.)

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 no sizing. Very absorbent.i.e. Blotting Paper.

Wax Pick -Important in checking surface strength that could affect linting and picking. Sticks of special wax of varying adhesive strengths (made by Dennison and rated 2A to 26A) are melted and applied to a sheet then pulled off when cool. The result is reported as the highest number wax that does not disturb the surface of the sheet. (This test should not be attempted on loose­ly felted papers or on coated papers contain­ing thermoplastic resins.) While the wax pick test is still widely used in the industry, its limited application has led to the use of other devices, particularly on coated papers.

Wove Paper -Papers which show no fine “laid” lines running through the sheet when held to the light.

…in addition to all that, there’s a continued glossary of general digital imaging terms.  See the Legion Paper main catalog/info sheet page here: Legion Papers

While you’re there if you see anything you like, shoot us an email for our pricing!

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