Paper glossary

The ability of paper or board to soak up or absorb aqueous solutions such as water, printing inks, varnishes etc.

The measurements of a paper´s light reflective qualities that affect contrasts and halftone reproduction. A paper with 85% brightness reflects 85% of the light that strikes it. Brightness increases the contrast between the ink and the paper and makes a document easier to read. Brightness is only a factor in white paper.

The thickness of paper relative to its weight. High bulk paper is thicker than low bulk paper, but not heavier. (See also: CALIPER)

The process of running paper between polished steel rolls on a paper machine to produce a desired smoothness. Uncoated paper is calendered in this sequence from roughest to smoothest: Vellum, Antique, Wove, Smooth. (Note: Superior smoothness and gloss can also be accomplished off machine by supercalender equipment.)

The thickness of a sheet, or stack of papersheets, as expressed in thousandths of a millimetre.

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 it 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%).

Pulp made by cooking the wood in the presence of chemical agents (acid or alkali) which eliminate the most non-fibrous material. 

Paper to which a coat has been applied on one or both sides, using a mix of clay, carbonates and latex to create a high quality printing surface.

A manufacturing plant which uses paper to make paper-based products, such as packaging or consumer products.

Deformation of a sheet of paper or board over its entire surface, which tends to roll up into the form of a cylinder.

Digital printing is defined as a printing job consisting of at least 30 sheets per minute directly from a database onto the paper. In its most simple form, a digital printing unit consists of a workstation, a raster image processor (RIP) and a printer.

Paper or board changes in its dimensions and flatness with variation in its moisture content and its termed dimensionally stable when such changes are of a low order.

Pulp bleached without chlorine gas.

A voluntary scheme for industrial companies, based on an EU directive.

Fine white pigment in the form of powder or slurry used to improve smoothness, opacity, brightness and dimensional stability of paper and board.  

The manner in which the fibres of a sheet of paper or board are distributed, disposed and intermixed to constitute the sheet.

Mass per unit is in gsm.

Creates images by ejecting tiny droplets of ink onto paper

International Organisation for Standardisation. An international organisation that has approved a range of standards extensively used in the paper industry.

An international series of standards covering quality management and quality assurance. The Finnish equivalent are ISO standards coded SFS-EN.

An international series of environment-related standards.

A high quality image printing system using a laser beam to produce an image on a photosensitive drum. The image is transferred onto paper by a conventional xerographic printing process.

The direction of a sheet or web of paper corresponding with the direction of the flow of stuff on the paper machine.

The percentage of moisture found in finished paper.

Stands for 'original equipment manufacturer', a company that manufactures and sells a product to another company for sale with its logo or brand.

Printing using a press and plate (indirect photo-lithography) in which the image is transferred to a rubber blanket which in turn offsets the image onto a sheet of paper. This type of printing can print continuous tone images and therefore provides much higher quality reproduction than the electrostatic process, particularly on photographs.

The amount of light that penetrates the paper and therefore the degree to which type shows through from the other side of the paper. Usually, the lower the basis weight, the less opacity.  

Paper is classified into different grades according to the end use, the pulp used and the treatment of the paper.

Paper which during long term storage in libraries, archives and other protected environments will undergo little or no change in properties that affect use.

A term denoting a number of sheets of paper ranging from 480 to 516, most commonly 500.

The mass of water vapour actually contained in a given volume of air expressed as a percentage of the maximum mass of water vapour that could be contained in the same volume at the same temperature.

Measure of air leakage between the surface of the paper and a flat metal ring. Expressed in ml/min.

The weight of a single sheet of one square metre (g/m2).

Machine for giving paper a very smooth surface by passing it through a series of alternate metal and composition rolls, revolving with high speed and pressure.

Totally chlorine-free pulp.   

The distance between surfaces of one sheet in micrometers (µm).

Tiny particles of a polymer which are heat-fused onto the page to produce laser printer images.

Paper to which this term applies retains an appreciable percentage of their mechanical strength after soaking in water, and made by the addition of a resin to the stock during paper manufacture. This resin cements the fibres together and the bond tends to improve with age. The advantages of printing maps on, or making certain wrappings from, wet strength paper are obvious.

The visual appearance of white paper, especially when it contains fluorescent whitening agents. It is based on reflectance data obtained over the full visual spectrum.

Wood-free i.e. chemical pulp-based paper is made of bleached chemical-based pulp, containing less than 10% of mechanical pulp.