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Glossary Of Papermaking Terms

Absorbency Aid: chemical additive that increases finished paper absorbency: sometimes called wicking. Typical chemistry is surfactant based.

Accepts: stock returned to system after screening or cleaners.

AKD Size: an internal size based upon Alkylketene Dimer (AKD) chemistry.

Alum: “Papermakers friend”- Aluminum sulfate, a cationic material used for a variety of applications in papermaking from pH reduction to precipitation or coagulation to affix other materials to the fiber. Used in latex and, dye fixative, and sizing applications.

Anionic Flocculant: a negatively charged high molecular weight polyelectrolyte water soluble organic polymer designed to agglomerate solids in water substrates.

Alkaline Papermaking: producing paper utilizing furnish that has a pH typically in the 7.0 – 9.0 range, many times with grades that contain calcium carbonate.

ASA Size: an internal size based upon Alkenyl Succinic Anhydride (ASA) chemistry.

Basis Weight: is a standard weight of a unit area of paper. Typically measured as a 500-sheet ream of paper of a particular grade. Usually reported as g/m^2

Biocide: chemical substance designed for killing living organisms in water. Often characterized by type of organism killed: bactericide, fungicide or algaecide.

Blind Drilled Roll: a roll in the press section that has drilled holes that allow water to be pressed from the sheet through the wet felt and into the roll. The water is expelled from the roll as it spins away from the press felt.

Boilout Chemistry: alkaline or acidic chemicals to clean the wet end, stock approach and paper machine areas. Typically contain other cleaning components to improve and optimize cleaning function.

Bone Dry Or Dry Weight: refers to the basis weight times minus % moisture.

Brightness: is the degree to which white or lighter shades of paper reflect the light of the blue end of the spectrum

Broke: (1) Paper trimmings or damaged paper due to breaks on paper machine and in finishing operations. (2) Paper which has been discarded during any stage in its manufacture; represents loss in time, money and effort.

Broke Pit: an area or pit below the machine which has a water source and agitator that operators can dispose of broke from the machine room floor.

Bulk: thickness of a paper in relation to its weight. If you compact a sheet you lower its bulk and increase its density.

Bulking Aid: chemical additive designed provide bulk to finished paper with minimal basis weight increases. This is accomplished by reducing inter-fiber bonding which leads to greater bulk.

Burst: a test procedure which measures a paper’s resistance to rupture.

Calender: after the paper is dried it is sometimes put through a calender or calender stack which is a series of hardened smooth pressurized rolls which imparts smoothness, flattening and glossiness to the sheet.

Cationic Flocculant: a positively charged high molecular weight polyelectrolyte water soluble organic polymer designed to agglomerate solids in water substrates.

Charge Control: cationic or anionic charged chemical to modify wet end charge demand.

Chemical Pulping: pulp production through the use of chemical cooking of wood chips. Primary chemical processes are sulfite and kraft.

Chemi-Thermomechanical Pulp (CTMP): when making pulp, this process adds chemicals to the chips before refining them. Typical chemistry is the addition of sodium sulfite heating to 120–130°C and followed by refining.

Chest: in papermaking, most tanks or vessels are referred to as chests. Many chests have an agitating or mixing device in them. Some also have a heat source such as steam.

Clarifier: typically used in the wastewater treatment area of a papermill, a clarifier is used to remove fiber and other impurities from the wastewater stream before discharge to a municipal wastewater facility or directly to a river or stream.

Coagulation: the destabilization of a colloidal suspension with salts or very low molecular weight, high charge density polyelectrolytes.

Coating: any material applied to a finished paper surface to impart additional specific properties.

Colloidal Silica: is a stable aqueous suspension of silicon dioxide (SiO₂). It is often used as part of a microparticle retention / drainage aid program.

Consistency: dry solids content of a wood pulp slurry in water.

Corrugated: a sheet of paper with either one or two faces with a fluted inner layer.

Couch Pit: a tank with an agitator below the wire forming section on a paper machine. The fiber and water that comes off the wire goes into the couch pit so the fiber can be captured and put back into the process.

Couch Roll: a vacuum roll at the end of the forming wire before the wet press section.

Cross Direction (CD): the direction of the paper perpendicular to the travel of the paper web on the paper machine.

Curl: a deformation in a sheet of paper typically on the edges due to uneven moisture and drying of the sheet.

Cylinder Machine: a type of paper machine that forms a sheet by utilizing forming cylinders that are composed of an outer wire and revolve in a vat of stock. As the cylinders revolve in the stock solution, fiber adheres to the wire until transferred to a wet fabric. Multiple vats/cylinders are utilized in line to make multi layered and differing weight sheets. Due to this unique process cylinder machines are typically used to make heavier grade sheets and also sheets with differing compositions in the comprising layers.

Dandy Roll: typically, a wire covered roll that sits over the wire forming section of the paper machine that compacts the fibers, helps to release air and otherwise provide top characteristics to the sheet.

Debonder: a chemical additive that is designed to provide bulk, reduce Mullen and impart softness to the finished paper. This is accomplished by reducing inter-fiber bonding which leads to greater bulk. Debonders are also called softeners.

Defoamer: chemistry designed to inhibit foam formation and/or reduce foam stability. Defoamer chemistries include Silicone, Fatty Acid / Fatty Alcohol, Oil Based and Ethylene Oxide / Propylene Oxide (EO/PO) block copolymers and glycols.

Deinking: the process or removing ink, and impurities from recycled fiber.

Digester: a pressurized vessel that breaks down fibers using heat and chemistry to produce pulp.

Doctor Blade: a metal or synthetic strip or blade that presses upon rolls and cylinders at a prescribed angle to remove any adhering foreign material.

Drainage: in papermaking the act of water removal though mechanical or chemical means.

Drainage Aid: papermaking additives designed help paper machine furnish release water in the forming section. Chemistries include cationic or anionic acrylamide copolymer flocculants and inorganic and organic coagulants.

Dry End: the section of a paper machine after the press section typically consisting of dryer cans, air dryers or other means. The sheet moisture at this point in the process is removed by evaporation.

Dry Strength: additives used to enhance paper strength. Dry strength chemistries include Starch, Glyoxalated polyacrylamides (GPAM) and acrylamide chemistries to improve fiber-to-fiber bonding.

Dryer Fabric: synthetic fabrics in the dryer section that is used to transport the sheet over the dryer cans to the reel.

Dryers: cylinders filled with low pressure steam in the dryer section that evaporates moisture form the sheet as it passes over them.

Dye Fixatives: cationic or anionic charged chemical to improve dye retention.

Effluent: wastewater from the paper process in a paper mill.

Felt Cleaners Or Washers: cleaners designed to clean paper machine wet and dry felts. Typically, alkaline, acidic or neutral pH cleaning formulations designed to clean wet or dry felts without damaging the fabric.

Felt Side: the side of a sheet of paper that touches the felt as it comes off the wire and into the press section.

Filler: the term “filler” refers to (1) any material added to the furnish to enhance specific sheet characteristics. (2) the inner layers of a multi ply sheet.

Fines: any small fillers or fibers in the papermaking process. Fines are typically small enough to pass through the wire.

Flocculation: process of forming fiber flocs. Aggregating colloidal particles through the action of high molecular weight, bridging polymers.

Fluff Pulp: is a type of chemical pulp made from long fiber softwoods such as pine.

Formation: refers to the orientation of the fibers and filler in the sheet of paper. This orientation affects the physical properties in a sheet of paper.

Fourdrinier: a type of paper machine composed of a headbox, flat wire forming section, press section and dryer section.

Fourdrinier Wire: although originally made of brass, it is now a plastic woven screen belt on a fourdrinier paper machine. The purpose of the wire is to from a sheet as the pulp exits the headbox. There are usually foils and vacuum boxes on the underside of the wire to aid in water removal of the sheet.

Freeness: a test which measures the paper furnishes ability to release water.

Furnish: the various constituents that make up the raw material for papermaking, including pulp, fillers, and chemicals. This will vary greatly due to different grades of paper.

G-PAM (Glyoxalated Polyacrylamide): glyoxalated polyacrylamides (GPAM) is a polymer that can be used as a wet strength, dry strength and drainage aid.

Groundwood Pulp: the pulp that is produced from debarked trees that are ground by a grindstone in the pulping process.

Hard Sized: paper that have a high degree of sizing treatments that make it very resistant to liquid penetration.

Hardwood Pulp: pulp derived from deciduous hardwood trees.

Head Box: the mechanical device that takes the pulp furnish and provides for even distribution onto the forming wire.

Holdout: laboratory term that refers to a sheet of paper’s ability to resist or “holdout” the surface penetration of a liquid.

Jet-To-Wire Ratio: the ratio of stock jet speed to the wire speed. It can impact sheet formation, strength, curl, directionality and shrinkage.

Kraft Process: predominant pulping process using sodium hydroxide and sodium sulfide chemistries to cook wood chips. The process disintegrates the chips into individual fibers which are further processed into pulp for the papermaking process.

Kraft Pulp: the pulping process that treatments wood chips with a hot mixture of hot water, sodium hydroxide, and sodium sulfide. As with other pulping process, it breaks the lignin bonds to produce pulp.

Lignin: natural ‘adhesive’ which binds wood fibers together in the tree. Most of this material is removed during lower yield chemical pulping processes. Higher yield pulping processes like groundwood, mechanical pulping and chemical-mechanical pulp retain a higher percentage of lignin in the pulp. This material can have some negative impacts on the paper like yellowing of the sheet and poor archival properties.

Linerboard: typically manufactured from recycled furnish is paper used for boxes and corrugated medium.

Machine Coated: paper and paperboard that have surface coating applied as a paper machine operation instead of an off-machine coating operation.

Machine Direction (MD): direction of the paper web as it is being manufactured on the paper machine.

Microparticle Retention Systems: paper making retention systems that combine polymers with very small particle to enhance retention and drainage. Microparticle chemistries include colloidal silica, clay and synthetic organic products.

Off Machine Coated: process of applying coating material to a web of paper or paperboard in an operation that is separate from the paper machine operation.

Opacity: the paper’s ability to transmit light through the sheet. It is impacted by fiber type, filler, refining, pressing, calendering, coatings and basis weight.

PAE (Polyamide) Wet Strength: additive to impart wet strength to paper. PAE wet strength is the predominate permanent wet strength used in paper making.

PFI Mill: laboratory pulp beating device. It uses a grooved roll and bed plate to refine and develop pulp fibers.

Pitich: a sticky material that can cause paper machine deposits and sheet defects. It is a naturally occurring resinous material found in trees and typically enters the paper mill through a pulp source.

Poly-DADMAC: poly diallyldimethylammonium chloride. High charge density, cationic polymer used for charge neutralization, retention programs and is a common titrant used in charge demand testing when the system has an anionic charge.

Polymer: large molecules that consist of many similar subunits (monomers) bonded together. They are usually categorized as low, medium or high molecular weight. A polymer charge can be cationic, anionic or nonionic.

Porosity: indication of void volume in the paper web. Usually tested by passing air through the sheet.

Preservative: a type of biocide that is provides longer duration killing of living organisms in water or water based systems. Preservatives are used to control microorganism growth in clays, pigments, starches, coatings, and saturating latex.

Press: the section of the paper machine that dewaters and compresses the paper web with a squeezing/pressing action. It is located after the forming section and before the dryer section.

Press Felt Or Fabric: a fabric in the press section that is utilized to press or vacuum water from the sheet. Typically, one or two fabrics with the sheet in between go through two rolls of which one or both have holes with or without vacuum to dewater the sheet.

Pulp: fibrous material used to make paper. The fibers are typically transported as a high moisture slush from a pulp mill or can be transported to a paper mill as a low moisture bale or roll.

Pulper: large blender-type piece of equipment that separates fibers using water and agitation.

PVSK: poly vinyl sulfonic acid, potassium salt. Common titrant used in charge demand testing when the system has a cationic charge.

Refining: the development of fibers using a disc or conical refiner. Mechanical energy is used to enhance the fiber structure to allow for improved fiber bonding and sheet properties.

Relative Humidity: actual amount of water vapor present in the air as compared with the maximum amount of water vapor the air could hold at that temperature (expressed at a percentage).

Release Aid: a release aid helps ensure that the paper sheet does not stick to rollers carrying the web during paper making or subsequent converting. The release aid is typically metered on to web carrying roller.

Retention Aid: papermaking additives designed help retain fiber and fillers during the wet end drainage process. Retention aid chemistries include cationic or anionic acrylamide copolymer flocculants and organic coagulants.

Rosin Size: an internal size based upon Rosin which is a naturally occurring resinous material from pine trees.

Saveall: a paper machine save-all is designed to remove fiber and other solids from white water so the clarified water and solids can re-used in the paper making process. Types of save-alls include disk or drum screens and dissolved air floatation (DAF) clarifiers.

Secondary Fiber: paper making fiber that has already been used to make paper or board. Also called broke, recycled or waste fiber.

Semichemical Pulp: wood pulp produced by a combination of chemical and mechanical means. The most prevalent process cooks wood chips in sulfite with an alkali such as sodium carbonate, sodium bicarbonate or sodium hydroxide. After being “chemically” cooked the pulp is mechanically refined to dissociate the fiber and washed to produce useable pulp.

Sizing: treatment of paper to resist liquid penetration, either by means of wet end (Internal) additives or surface application. Internal sizing chemistries include Alkyl Ketone Dimer (AKD), Rosin and Alkyl Succinic Anhydride (ASA). Surface sizing chemistries include modified starches, Styrene Maleic Anhydride (SMA), Styrene Acrylic Emulsion (SAE), Styrene Acrylic Acid (SAA), Ethylene Acrylic Acid (EAA), gelatin and Polyurethane (PUR).

Size Press: a two rollers nip that the paper passes through and a liquid size or coating is applied to the paper. The size press is typically positioned between two dryer sections.

Sizing Agent: additive used to improve water resistance and strength. Internal sizing chemistries include Alkyl Ketone Dimer (AKD), Rosin and Alkyl Succinic Anhydride (ASA). Surface sizing chemistries include modified starches, Styrene Maleic Anhydride (SMA), Styrene Acrylic Emulsion (SAE), Styrene Acrylic Acid (SAA), Ethylene Acrylic Acid (EAA), gelatin and Polyurethane (PUR).

Slurry: papermaking slurry is a mixture of suspended solids in water. Papermaking furnish (pulp, additives and retention aids), liquid clays or other liquid pigments are typically slurries used in papermaking.

Slimicide: a Slimicide (also called Biocide) is a Chemical substance designed for killing living organisms in water. Often characterized by type of organism killed: bactericide, fungicide or algaecide.

Softener: a chemical additive additive that is designed to provide bulk, reduce mullen and impart softness to the finished paper.. This is accomplished by reducing inter-fiber bonding which leads to greater bulk. Softeners are also called debonders.

Softwood: wood from a conifer tree such as pine, spruce, fir or hemlock tree.

Starch: polymer of glucose derived from various plants, principally corn, tapioca, potato and wheat. It is widely used in papermaking as a dry strength additive, as the major component in surface sizing solutions and as an adhesive in coating formulations.

Stickies: stickies is the name given to tacky substances in pulp, recycled fiber and paper making water systems. They are typically contamination from adhesive contained in post-consumer waste fiber. Chemical additives can be added to help minimize stickies problems in paper making.

Stock: slurry mixture of fiber, additives and retention aid that is used to form paper and paperboard.

Surface Sizing: water resistance chemistries that are applied to paper or paperboard’s surface. Typically applied in a size press to provide improved water, ink or other fluid hold-out or resistance. Surface sizes include starch and latex based coatings.

Synthetic Fiber: manmade fibers used in paper or non-woven manufacturing. Fibers include polyester, polyethylene, polypropylene, nylon and Kevlar. Synthetic fibers provide finished paper properties that are difficult to achieve with wood (cellulose) based fibers.

Talc: talc is a soft clay like mineral composed of magnesium silicate Mg3SiO4O10(OH)2 that is used in paper making to control pitch and stickies. It reduces the tackiness of these contaminants.

Tear Strength: strength measurement of paper or paperboard’s resistance to tearing. Both edge and internal tear strength are important physical properties. Edge tear strength is typically measured using the Finch Method: TAPPI T 496 Edge Tearing Resistance of paper. Internal tear strength is typically measured using the Elmendorf Method: TAPPI T 414 Internal Tearing Resistance of Paper.

Tensile Strength: strength measurement of paper or paperboard’s resistance to breaking. The amount of force required to rupture the paper is measured. Typically measured using TAPPI tensile test T-404 or T–494.

Uhle Box: is a box shaped structure in the press section that is used to remove water from a paper machine’s press felts. A vacuum is typically applied at the Uhle box to help remove water from the wet felts thus improving the press section’s performance. The Uhle box is also called a vacuum box.

Vacuum Box: is a box shaped structure in the press section that is used to remove water from a paper machine’s press felts. A vacuum is typically applied to help remove water from the wet felts thus improving the press section’s performance. The Vacuum Box is also called a Uhle Box.

Wax Emulsion: waxes are highly hydrophobic substances that can be used for internal and external sizing. Waxes are typically emulsified for paper making applications. Wax emulsion can be used as a stand-alone size or in combination with rosin size.

Wet End: a paper machine’s wet end is the initial part of the machine through the wet press section. It is the part of the paper machine that is designed to dewater the very low solids furnish (fiber and other additives) and form it into paper or paperboard that is dried in the press and dryer sections. These wet-end parts include the headbox, forming sections and wet press section.

Wet Strength: additive to impart permanent or temporary wet strength to paper. Chemistries include Polyamide (PAE), Glyoxalated polyacrylamides (GPAM), urea-formaldehyde and melamine formaldehyde chemistries, added to the papermaking stock, to impart permanent or temporary wet strength to the paper.

Wire: although originally made of brass, it is now a plastic woven screen belt on a fourdrinier paper machine. The purpose of the wire is to from a sheet as the pulp exits the headbox. There are usually foils and vacuum boxes on the underside of the wire to aid in water removal of the sheet. Also called a Fourdrinier wire.

Wire Cleaners: cleaners designed to remove contaminants from paper machine forming wires. These cleaners are designed to remove tough clean contaminants including pitch, resin, stickies and adhesives.