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A
ABSORBENCY
The ability of a paper to take in liquids such as ink and varnish
ALKALINE PAPER
Paper manufactured under operating conditions with a pH greater than 7.0.
B
BASIC SIZE
Basic sheet size for bond and ledger is 17" x 22"; offset is 25" x 38"; cover is 20" x 26"; index is 25.5" x 30.5"; and tag is 24" x 36".
BASIS WEIGHT
A fixed weight per 500 sheets of paper (one ream) of different paper grades weighed by their designated basic sheet size.
BRIGHTNESS
Brightness is measured as the percent of light at a certain wavelength (457 nanometers) that is reflected from the surface of a piece of paper. High brightness papers give a greater contrast with black inks and a more lively appearance with color inks.
There are 3 methods considered as "standard brightness measurements". These approaches differ in the light source and geometry used in the equipment making the measurements to describe paper brightness levels.
- GE Brightness instruments use "directional" illumination geometry with standard light source mimicking "indoor" lighting to measure the reflectance of the wavelength.
- ISO Brightness, C Illuminant, instruments use "diffuse" illumination geometry with a standard light source mimicking "indoor" lighting to measure the reflectance of the wavelength.
- ISO Brightness, D65 Illuminant, instruments also use "diffuse" illumination geometry, but with a standard light source mimicking "outdoor" lighting, to measure the reflectance of the wavelength. This method is commonly used in Europe, and produces measurements greater than 100% in the higher brightness papers.
C
CALIPER
The thickness of a sheet of paper, expressed as thousands of an inch, or points. Caliper is important where the page count per inch is specified. Uniform caliper is needed for uniform printing and for runnability in converting processes.
CURL
Curl is the tendency of paper to not lay flat. Printing papers designed for use in offset printing processes should be manufactured with as little curl as possible to support good runnability and feeding through the press, finishing and binding equipment. Tight curl control is also important to prevent jamming in the xerographic or laser imaging equipment.
F
FELT AND WIRE SIDES
Refers to the top and bottom surfaces, respectively, of paper made on conventional fourdrinier paper machines. In general, the felt side contains a higher percentage of fillers and short fibers than the wire side. However, modern paper machines, such as twin wire machines, largely eliminate these differences.
FORMATION
Formation is judged by transmitting light through the sheet and looking at its structure and degree of uniformity. Paper with good formation prints with less mottling and has more uniform opacity.
FURNISH
The combination of materials and chemicals that go into making the pulp stock mixture. The mixture is fed into the paper machine at the wet end of the machine. Also referred to as Stock Furnish.
G
GRAIN
Refers to the alignment of fibers in the direction of their flow on the paper machine. Folding and scoring work best when done in the paper's grain direction. Grain also affects tear strength, stiffness and dimensional stability.
M
M WEIGHT
The weight of one thousand sheets of a grade in its basic size
MICR
This stands for "Magnetic Ink Character Recognition", a standard machine language technology designed for paper document based payment transfer systems. It utilizes specially designed magnetic ink printed characters that can be recognized by high-speed magnetic recognition equipment.
MOCR
This stands for Magnetic/Optical Character Recognition and is used by the paper industry to denote papers designed to perform in both OCR and MICR applications.
MOISTURE CONTENT
This is the amount of moisture contained by paper, expressed as a percentage of its total weight. Uniform moisture is a necessity in all grades of paper.
O
OCR
This stands for "Optical Character Recognition", a scanner-based technology to digitize and "read" printed text and characters. ANSI and Government Printing Office standards have been developed which establish key paper attributes required for optimal performance in the majority of devices. As technical advances have occurred, these standards have been revised accordingly.
OPACITY
The ability of paper to obstruct light transmission and the show-through of printing. It is particularly important in two-sided printing. It also affects readability and overall appearance. Opacity is improved by scattering, absorbing or reflecting light. Fillers such as titanium dioxide and calcium carbonate scatter light, while blue and violet dyes absorb it. Therefore, more opaque papers are generally a more blue-white shade.
P
PERMANENCE
Refers to paper's ability to maintain certain physical properties over time, such as brightness and strength. Especially common is the discoloration of some papers, which turn from white to yellow with age.
POROSITY
This property measures a paper's resistance to air permeation through the sheet. A higher number means the sheet is less porous. Higher porosity measurements support decreased ink consumption on offset papers. In converting equipment or high speed sheet fed printers where vacuum pick-up or transfer systems are used, higher porosity prevents misfeeds and double feeding of paper, improving its runnability.
R
RECYCLED CONTENT PAPER
A paper product that contains recovered paper materials. The recycled content is measured as a percentage of the paper's weight.
RESTIVITY
Measures the "resistance" of a material to conduct electricity. This property is controlled in xerographic or electrostatic-based imaging systems for proper image quality.
S
SIZING
Sizing is added to offset and imaging papers in the manufacturing process primarily to control the absorption properties of the paper in end use applications. Internal sizing in paper affects the overall strength properties of the sheet and absorbency and permanence characteristics of the ink in end use applications. Surface sizing is also used in the paper making process to improve the sheets surface strength characteristics, to improve bonding of the surface fibers to the sheet, and to control absorption and feathering performance of the paper in end use applications with offset printing inks and in ink jet printers.
SMOOTHNESS
A measured property of paper that describes or rates the flatness and evenness of a sheet's surface.
STACK LEAN
The tendency for perforated and fan-folded forms to "lean" rather than form vertical stacks. This condition may be caused be improper equipment adjustment, particularly if the lean is from front to back in the machine direction. Internal stresses or "dimensional stability" issues in the paper that are influenced by temperature and humidity may also cause side to side or diagonal lean. Using paper that is engineered to remain stable when exposed to high temperatures or variable humidity conditions can minimize this tendency (see also TSO).
STRENGTH
Measured by tests for burst, tear, tensile and folding strength. All printing papers need strength to run through equipment at normal production speeds.
SURFACE BONDING
Refers to resistance of surface fibers to separating or "picking." Picking can become a problem if the ink is too tacky or if there is too much pressure on the impression cylinder.
T
TSO
Stands for "Tensile Strength Orientation" a measurement technology that quantifies the propensity of a material to expand non-uniformly when exposed to variable humidity and/or temperature. This technology is typically used by the paper industry as a controllable predictor of dimensional stability in various imaging and printing applications (see also Stack Lean).
W
WEB
A continuous length of paper, such as paper when it is on the paper machine or on roll-feed equipment.
WICKING
The tendency for a liquid, such as ink, to feather or move on the surface of a sheet of paper or through the paper to the other side.
X
XEROGRAPHIC COPYING/PRINTING
An electrostatic, non-impact printing process in which intense heat fuses dry toner particles to electrically charged areas on the paper to create an image. The charged areas of the paper appear black on the copy, while the uncharged areas remain white.
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