Explanation of some commonly used paper industry and papermaking terminology referred



The property that causes paper to take up liquids or vapors that comes in contact with it.
Acid Free Paper
A paper manufactured to a neutral pH reading. Used for fine art prints, limited edition printing, permanent records and to protect other materials where contact with paper acidity would be harmful
Acid paper
Paper using clay or Magnesium Silicate (Talc) as the predominant filler and an acidic rosin-aluminum mixture as the primary internal sizing agent.
Degree of acid found in a given paper measured by the pH factor. pH is measured from 0 -14, with 7 representing neutral between acid and alkaline. From 0 - 6 is considered acid, from 8 - 14 alkaline. Papers manufactured in Pakistan are generally acid papers.
Against the Grain
Folding or feeding paper at right angles to the grain direction of the paper.
Alkaline paper
Paper using calcium carbonate as the filler and a synthetic material, compatible with the alkaline process, as a sizing agent. This process increases the longevity, bulk, brightness, opacity and printing characteristics of the paper while decreasing cost.
A reservation/booking of paper/board from inventory to fill a customer order. In Pakistan, it is specifically used for large Provincial Textbook board orders to printers as high as 18,000 metric tons.
Antique Finish
A term describing the surface, usually on book and cover papers, which has a natural rough finish.


The back-edge of a bound book connecting the two covers; also called the spine.
Backing up
Printing the reverse side of a sheet already printed on one side.
Basic Size
The one size in each category of paper that is used to establish the weight of the sheet. Basic sizes differ from category to category. Copy papers have a basic size of 27 x 34 and 17 x 27; book, offset, and text papers have a basic size of 23” x 36” and 20” x 30”.
Basis Weight
The weight in pounds of a ream (500 sheets) of paper cut to its basic size. For example, 500 sheets of basic size 20 x 30, 60 grams paper will weigh 11.61 kg. The phrases "basis weight" and "substance" are often used interchangeably.
In offset-lithography, a rubber/polymer-surfaced sheet clamped around the cylinder of the press to receive ink from the plate, which transfers the image from plate to paper.
Pulp fibers are generally bleached to produce white fibers for papermaking. Other reasons are to increase the chemical stability and permanence of wood fibers by chemical purification and to obtain clean, sanitary fibers as required for food packaging papers.
Refers to the printed image extending beyond the trim edge of the sheet. This generally takes place when the paper has not been properly dried or is highly hygroexpansive.
When printing on one side of a sheet of paper shows through to the other side.  Lack of opacity or inferior printing inks age also general causes of this condition. Excessive ink application can also cause this problem.
Separation of the paper's coating from the body stock which appears in the form of eruptions. Caused when paper is dried too quickly during the manufacturing process.
Bonding strength
Cohesiveness of fibers within paper. Paper with good bonding strength will not pick during the printing process.
Book Paper
A general term for coated and uncoated papers with the basic size of 23” x 36”
Total rupture of a web of paper during the manufacturing or printing process, resulting in a tear from edge to edge. Breaks in mill rolls are sometimes spliced together and marked with flags to call the attention of press operators to potential difficulties.
The reflectance or brilliance of the paper when measured under a specially calibrated blue light. Not necessarily related to color or whiteness.
Property of paper causing it to break while bending.
The degree of thickness of paper, often expressed in hundredth of a millimeter.
Bursting strength
A measurement of the strength of paper to withhold pressure.


A process on the paper machine where the paper is squeezed between metal cylinders to compact the fibers. This makes the paper smoother and imparts some gloss.
The thickness of a sheet measured under specific conditions. It is usually expressed in thousandths of an inch (points or mills). Caliper is affected by paper moisture content and the pressure applied to the wet presses and calenders. Caliper is particularly important when printed materials need to be folded, inserted, and mailed using automatic handling equipment. Variations in caliper across the sheet will cause problems such as loose edges and baggy areas.
Cast Coated Finish
Made by depositing a clay-based coating on paper which is then run over a heated chromium plated drum. This produces a level mirror-like finish.
Chain Lines
The more widely spaced watermark lines which run with the grain in laid paper. Caused by "chain wires" which are twisted around the laid wires to tie them together. They are usually about one inch apart.
A fine-grained mineral material used as filler in papermaking or as coating pigments.
Coated paper
Paper with a surface coating imparting a smooth finish. Coated paper finishes have a higher opacity and better ink holdout than uncoated papers.
An emulsion, varnish or lacquer applied over a printed surface to protect it.
Cockle Finish
Produced by air-drying paper with controlled tension. This uneven surface is available in bond papers.
Allowing the temperature and moisture content of paper packed in cartons and skids the necessary time to reach equilibrium with surrounding atmospheric conditions prior to printing.

Cross Direction (CD)
Direction or dimension at right angle to the flow through of a papermaking machine; the direction across the grain. Paper is weaker and more sensitive to changes in relative humidity in the cross direction than in the grain direction.
A condition of a dried ink film, which repels another ink printed on top of it.
The distortion of a sheet due to differences in structure or coatings from one side to the other, or due to absorption of moisture on an offset press.
Refers to business or writing papers that have been cut to dimensions of 8 1/2x11 and 8 1/2x14 or 11x17.


Dandy roll
(1) A plain roll situated above the wet web of the paper to provide a smoothing action to the top surface of the paper as it passes under the roll (2) A watermarking dandy roll is a roll of skeletal structure, sheathed in a wire cloth that has designs, letters or figures affixed to it. As the wet paper web passes under the turning watermarking dandy, the designs are impressed into the paper and a permanent watermark is left in the sheet.
Deckle Edge
The untrimmed, feathery edges of paper formed where the pulp flows against the deckle.
Digital Color Printing
A printing process that allows color printing directly from electronic images without the need for film or color separations.
Dimensional Stability
The ability to maintain size. The resistance of paper to dimensional change with change in moisture content or relative humidity.
A series of large, cylindrical steam heated rolls that dry the paper webs to the final moisture content.
Dry finish
Term indicating that paper or paperboard is calendered without use of water. Also, paper with unglazed, rough finish obtained by the dry finish process.
An exact, handmade format sample created with blank paper to show the desired size, shape, weight and general appearance of a project prior to production.
Duplex Paper
Paper with a different color or finish on each side, usually produced by laminating two sheets of paper together.


Elmendorf test
A test to determine a paper's resistance to tearing.
Embossed Finish
The overall design or pattern impressed in paper when passed between metal rolls engraved with the desired pattern. Produced on a special embossing machine after the paper has dried to create finishes such as linen.
A general term for coated papers.
English finish
A smooth-finished, machine made and calendered book paper. It is soft, dull and pliable. Normally used for letterpress printed magazines.
Equivalent weights
System of comparing papers of different basic sheet sizes and basis weights. i.e. 90lb (25 1/2 x 30 1/2 - 500) is equivalent to 100lb (24 x 36 - 500)


Felt Finish
Uncoated, uncalendered surface texture produced by using patterned felt belts and pressure in forming paper on the paper machine.
Felt Side
The side of the paper which does not touch the wire on the paper machine. The "top side" or felt side is preferred for printing because it retains more fillers.
The most important physical property of paper. It describes surface contour and characteristics measurable by smoothness, gloss, absorbency and print quality. With regards to bristols, there are three uncoated finishes (wove, vellum and high bulk) and three coated finishes (matte, dull and gloss).
Paper that measures 17 x 22 (374 square inches) and longer.
Four-color process
Primary process ink colors: magenta (red), cyan (blue), yellow and black.
Free Sheet
Paper that contains little or no mechanical wood pulp (groundwood).


Grain Direction
The direction in which most of the fibers lie in a finished sheet of paper which corresponds with the direction the paper is made on a paper machine. Fibers flow parallel to the direction in which the paper travels on the paper machine during manufacturing.
Grain Long
The grain of paper is parallel to the long dimension of a sheet of paper. For example, 25 x 38, grain long, indicates that the grain is traveling in the 38 inch direction.
Grain Short
The grain of the paper is parallel to the short dimension of a sheet of paper, or at right angles to the long dimension. For example, 23 x 35, grain short, indicates that the grain is traveling in the 23 inch direction.
Groundwood Pulp
A mechanically prepared wood pulp used in the manufacturing of newsprint and publication papers.


A printed picture that uses dots to simulate the tones between light and dark. Because a printing press cannot change the tone of ink, it will only print the ink color being used on the press. This works well for printing text or line art: the press simply puts a full dose of ink for each letter or line on the paper, creating small solid areas of ink.
Hickeys are caused by solid particles that adhere to the plate or blanket and are ink receptive.

Doughnut-shaped hickeys, which have a black speck in the middle and are surrounded by a white halo, can come from ink particles, greasy dirt from the press, particles of press rollers breaking down, or chips of paint from the ceiling. Occasionally, coating lumps or scale may accept ink and produce doughnut-shaped hickeys. They should not be confused with paper dust as paper dust clings to a blanket, absorbs water, resists ink, and causes a white speck.

Paper particles can absorb water and generally print as voids, but eventually they do become ink receptive and will print as a hickey. However, inside the doughnut you will always see some white in the center. Hickeys and their sources, although infrequently a paper-related problem, can be analyzed with a magnifying glass.
Term refers to the ability of a sheet to resist penetration by liquid substances such as ink.


Index bristols
Manufactured on Fourdriner machines from chemical wood pulp. Index bristols are characterized by strength, ruggedness, and erasability.
Ink Holdout
The degree to which a paper surface resists penetration of ink. An inked image printed on paper with a high degree of ink holdout will dry by oxidation rather than absorption.


To shake a stack of papers, either on a machine or by hand, so that the edges line up. Printers jog the paper to get rid of any dust or particles, and to ensure proper feeding into the press.
Junior cartons
Any sheet measuring less than 374 square inches. Usually ream wrapped and packed in cartons.

A paper containing unbleached wood pulp (brown in color) made by the sulfate process.


Laid Lines
The closely spaced light lines in laid papers produced by the laid wires on the dandy roll. Laid lines usually run across the grain of the paper.
Laid Paper
Paper with a pattern of parallel lines at equal distances, giving a ribbed effect.
Paper that is developed by fusing one or more layers of paper together to the desired thickness and quality.


M Weight
The weight of one thousand sheets of paper, any size; or double the ream weight.
Machine Coated
Paper which is coated on one or two sides on a paper machine.
Make ready
All work done to set up a press for printing.
Matte Finish
A dull, clay-coated paper without gloss or luster.
Mechanical Pulp
Groundwood pulp produced by mechanically grinding logs or wood chips. It is used mainly for newsprint and as an ingredient of base stock for lower grade printing papers.
Moisture content
Refers to the amount of moisture found in a sheet of paper. Average amount ranges from 4 - 7%.
Mullen Tester
A machine for testing the bursting strength of paper.

Paper made mostly from groundwood pulp and small amounts of chemical pulp.


Offset Paper
Paper that is sized-internally or externally (see sizing) and contains the quality characteristics needed in order to print on offset presses. Offset presses print by transferring ink form the printing plate onto a rubber blanket and then to the paper.
That property of paper which minimizes the "show-through" of printing from the back side or the next sheet.


Paper Grade
Papers manufactured to fit within a group or type of papers. Each grade of paper uses basically the same fiber, color, additive and chemical composition.
The pulling out of paper fibers from the paper surface during printing. It occurs when the pulling force (tack) of the ink is greater than the strength of the paper.
The solid particles in inks rendering body, color or opacity.
Equal to one thousandth of an inch in the measure. Utilized when the thickness of paper is considered.
The property of paper that allows the permeation of air, an important factor in ink penetration.
Pressure-Sensitive Paper
Material with an adhesive coating, protected by a backing sheet until used; will stick without moistening.
Print Quality
The properties of the paper that effect its appearance and the quality of reproduction.


Rag paper
Historically, paper made with rag pulp. Today it is usually referred to as cotton fiber paper. It may be made from cotton cuttings (rags), linters or other waste cotton. End uses are principally high grade bond, ledger and writing, and papers required for permanent record purposes.
Five hundred sheets of paper
Relative Humidity
The amount of water vapor present in the atmosphere expressed as a percentage of the maximum that could be present at the same temperature.
Equipment used to slit a large width roll into a smaller width. It takes reels from the paper machine, unwinds the web, slits it and then rewinds the web onto small fiberboard cores. This allows the mill to make a multitude of roll widths and diameters to meet specific customer orders.
Paper properties that affect the ability of the paper to run on the press.


SBS (Solid Bleached Sulphite)
A type of heavy-weight board which is a single thickness run on a Fourdriner paper machine. Board run on a cylinder paper machine has several thicknesses (or ply) laminated together.
To impress or indent mark with a string or rule in the paper to make folding easier.
The undesirable condition in which the printing on the reverse side of a sheet can be seen through the sheet under normal lighting conditions.
The treatment of paper which gives it resistance to the penetration of liquids (particularly water) or vapors. Sizing improves ink holdout.
Describes or rates the flatness and evenness of a sheet's surface
The ability of paper or paperboard to resist an applied bending force and to support its own weight while being handled. A sheet that is too limp can cause feeding and transport problems in copiers and printers. An adequate degree of stiffness is important to avoid distortion of the paper due to the pull of ink during offset printing. Stiffness is critical to many converting operations for forms and envelope grades.
Paper or other material to be printed.
The penetration of ink through paper.
Stub roll
Usually refers to a small-diameter roll or a roll with only a small amount of paper remaining on the roll.
The weight in pounds of a ream (500 sheets) of paper cut to the standard size for business papers. Alternative word for basis weight.
Sulphate Pulp
Paper pulp made from wood chips cooked under pressure in a solution of caustic soda and sodium sulphide. Known as Kraft pulp.
Sulphite Pulp
Paper pulp made from wood chips cooked under pressure in a solution of bi-sulphite of lime.
Alternating rolls of highly polished steel and compressed cotton in a stack. During the process the paper is subjected to the heated steel rolls and "ironed" by the compressed cotton rolls. It imparts a high gloss finish to the paper. Supercalender stacks are not an inherent part of the paper machine, whereas the calender rolls are.  


The degree of pulling power (stickiness) in printing ink. An ink with excessive tack tends to stick to the impression blanket rather than successfully transferring to paper during the printing process.
A characteristic of paper, a slightly rough finish, which permits it to take ink readily.
Transparent ink
Ink which permits previous printing to show through, permitting the two colors to blend and produce a third.
The property denoting a difference in appearance and printability between its top (felt) and wire sides.


UV Coating
Ink specially formulated to dry quickly with ultraviolet (UV) light while still on press. UV drying improves turnaround time because it eliminates waiting time for the first side to dry before printing the second side. This eliminates the need for the paper to pass through the press more than once.


A coating printed on top of a printed sheet to protect it, add a finish, and/or add a tinge of color. An entire sheet may be varnished, or certain areas, like halftones, may be spot varnished to add emphasis and appeal.
Vellum Finish
Uncoated, toothy, "soft" finish in fine paper.


Process of cleaning the rollers, plates, blankets and sometimes the fountain of a press.
The image impressed into the formation of paper by the dandy roll on the wet end of the paper machine; can be seen by holding the watermarked sheet up to the light. Can be either a wire mark or a shaded image.
Wax pick
A test to determine the surface strength of paper or board. This test evaluates surface bonding strength and relates to the tendency for tacky inks to pick fibers or particles from paper surface.
A continuous sheet of paper on a paper machine in roll form.
Whiteness of pulp and paper is generally indicated by its brightness, which is the reflectance of a wavelength of blue light. So-called white papers have a definite hue. Most are made with a blue white tint.
Wire Side
The side of a sheet next to the wire in manufacturing; opposite from the felt or top side; usually not as smooth as the felt or top side.
With the Grain
Folding or feeding paper into a press parallel to the grain of the paper.
Wove Finish
Uncoated, uncalendered paper with a relatively smooth finish. Most common in uncoated offset, writing, and envelope papers.


The printing process used by photocopying machines. Electric charges create the image on an electro photographic surface that works as a plate. This surface is cleared after each copy is made, and used over again for the next copy.