Explanation of some paper industry and papermaking terminology

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Stock or pulp preparation:
Pulping - dry pulp is dispersed into water to form a slush or slurry. The operation can be either batch or continuous.
Beating and refining - the fibres are subjected to mechanical action to develop their optimal papermaking properties with respect to the product being made.
The operation is usually continuous, but some pulps are still treated batch-wise.
Shives - small bundles of fibres that have not been separated completely in the pulping operation.
RCF - recycled fibres.
OCC - old corrugated cardboard
DIP - de-inked pulp.
Flotation cell - part of the de-inking process, millions of tiny air bubbles are injected into the cleaned pulp, the free ink particles attach themselves to these bubbles and float to the surface where it is skimmed off and removed.
Disperger - process of fragmenting unwanted particles without damaging the wanted pulp fibres.
Virgin pulp/fibres - pulp/fibres from trees.
Softwood - cone bearing trees, since they normally keep their needles or leaves the entire year, they are referred to as evergreens.
Softwood fibres are long in relationship to hardwood fibres.
Hardwood - wood from trees of the angiosperm class, usually with broad leaves and deciduous in temperate zones.
Hardwood fibres are short in relationship to softwood fibres.
Fines - very small fibres and fibre fragments.
Fillers - addition of minerals to fill the voids between the fibres.
Ash - residue after paper is burnt - see Fillers
Furnish - combination of different pulp types required to manufacture different grades of paper.
White water - drained water from the papermaking process contains short fibres, fines and fillers, and is fed back into the
process.

Basic components of a paper machine are:
Stock inlet (flowspreader) - the objective of the inlet piping is to distribute the papermaking fibres uniformly across the machine from front to back.
Forming table - an arrangement of a moving mesh (known as a wire) running between a breast roll and couch roll passing over over a sequence of foils and vacuum elements, objective is to receive the diluted stock from the headbox, start the process of removing water but retaining the pulp fibres which starts forming a paper sheet, also to cause sufficient turbulence to ensure an even formation of the fibres throughout the sheet. Also known as Fourdrinier after the inventor.
Press section - the sheet is conveyed through a series of presses where additional water is removed and the web is consolidated (i.e., the fibres are forced into intimate contact).
Dryer section - most of the remaining water is evaporated and fibre bonding develops as the paper contacts a series of steam heated cylinders.
Size press - a dried sheet is passed through a wet press where size is added for improved sheet properties, the now wet sheet requires drying a second time.
Infrared dryers - special application - can use either gas-fired or electric supplementary IR dryers. IR is a non-contacting drying process for immobilising wet coating applications to prevent problems when the web makes contact with steam drying cylinder, IR can also be used at the end of the paper machine for final sheet moisture profile control.
Re-wetting/re-moisturising - special application - controlled spraying of hot atomised condensate water onto a partly dry sheet within the drying section, aim is to eliminate dry streaks and create an even moisture profile at the reel.
Calender section - the dry final sheet is pressed between metal rolls to reduce thickness (caliper), give an even thickness across the width of the sheet, and also smooth the top and bottom surfaces.
Soft calender - variation on the on machine calender where paper is passed between one hard roll and one soft covered roll, then one soft and one hard roll, this has the advantage of minimising bulk loss while still achieving smoothness properties on both sides of the paper.
Hot calender - using heated calender rolls, starts to plasticise the surface fibres, thus improving gloss and smoothness properties.
Supercalender - additional process after the paper machine, supercalender consists of a series of rolls arranged vertically, consisting of alternate hard and soft rolls (compressed fibrous material). Typically used to develop smoothness and gloss in
such products as coated and uncoated high-quality printing papers.
Janus calender - a variation of the supercalender mounted at 45 degrees but located on the paper machine before the reel.
Reel - final part of the paper machine requires dried paper to be wound onto a reel or spool, with the facility to remove the reel when full, also transferring the paper sheet to a new empty reel, all as a continuous process
Tail feeding - process of threading a narrow sheet through the paper machine from forming table to the reel at full machine speed before establishing a full width sheet, using a combination of ropes, air-jets and vacuum conveyors, depending on speed and configuration of the paper machine.
Winder - (also known as re-winder) the first part of the conversion process after the paper machine, the reel of paper is unwound and rewound under tension, also trimmed at edges to give a clean cut, options include slitting into custom width reels, all depending on conversion to final product.

Some mechanical properties terms used in papermaking:
Basis weight, grammage or substance - gross weight of the paper per unit area, typically g/m² (gsm).
Moisture content - water weight measured as a percentage of total basis weight
Dry weight - basis weight less water weight.
Conditioned weight - calculated basis weight using a fixed or predicted moisture content, dry weight + fixed moisture weight
(typically used in tissue manufacture).
Caliper - thickness of one ply of paper, typically measured in microns or mm.
Density - g/cm³.
Bulk - reciprocal of density - cm³/g.
Ash - mineral content as percentage of total basis weight.
Formation - interpretation of how fibres are distributed in the sheet.

Optical properties used in paper making:
Brightness (Elrepho) - measured as percentage.
Opacity - measured as percentage.
Gloss - measured as percentage.
Dirt count - count of visible dirt particles in final sheet, ppm.
Colour - L,a,b. interpretation of lightness and shade.

Other terms used in the paper making:
MD - machine direction or forward movement on the paper making machine.
CD - cross direction is right angles to the machine direction.
Profile - graph showing variations in CD properties.
Trend - graph showing variation in MD properties relative to time
DCS - distributed control system.
WBA - web break analysis.
WMS - web monitoring system.
WIS - web inspection system.
QCS - quality control system, requires sensors mounted on a continuously scanning frame to measure, display and control various MD and CD properties, e.g., basis weight, moisture, ash and caliper. QCS available for other industries including rubber, plastic and metals, as well as paper industry.
Stickies - large non-fibre contraries in the the sheet.
Broke - paper manufactured out of specification, normally re-pulped and used again.
Trim squirts - adjustable position water jets cutting the edge of the sheet to the desired width at the forming or press section.
Deckle - width of paper on the machine.
Yankee cylinder - single large diameter drying cylinder used in tissue and towel products.
MG cylinder - similar to Yankee, but used on other grades of paper, stands for Machine Glaze, the sheet in contact with one large hot dryer for a long dwell time will start to slip and plastisise the surface fibres, improving gloss & glazed properties on one side of the paper, e.g. manila envelopes.
Creping - achieved by using a doctor or creping blade to aid release of dried tissue from adhering to the Yankee cylinder.
Through dryer - sometimes used in tissue and similar grades where bulk cannot be sacrificed, the through dryer replaces a conventional press for water removal, hot dry air is passed through the voids in the sheet.
Air turn - used where a wet coated sheet need to change direction without contacting any rolls or cylinders, a cushion of air is created from a static roll, and the sheet follows this a few mm away from the surface.
Flotation dryer - non contacting dryer used in coating applications, drying is achieved by passing sheet between two hoods where hot dry air is impinged onto the sheet and the moisture is evaporated and removed by an air system.
LAS - Liquid application system, variation of the size press, liquids can be metered and applied to the sheet with high precision.
Steam showers - installed on forming table or within the press section before a press nip, works by raising the temperature of the sheet and its inbound water, resulting in dewatering and press efficiencies.
Efflux ratio - ratio of speed of the stock to the speed of the wire, important for achieving desired sheet formation, inverse is rush-drag.
This glossary is available as a .pdf file download pdf

Some images of the paper making process can be seen here http://millsight.com/machinevision-applications/applications/image-examples/

This popular page is not intended to be a definitive and comprehensive glossary, however we welcome any comments (favourable or other) including suggestions, additions or corrections. comments form