Glossary
A list of commonly used terms in industrial papermaking, with simple definitions
| TERM | DEFINITION |
| Abrasion | 1. The susceptibility of the surface of a paper sample to being abraded during a standard test. 2. The tendency of papermaking materials to abrade slitter knives, dies, etc. |
| Acicular | Another word for “needle-shaped,” as in the case of aragonite calcium carbonate particles |
| Acid alum | A mixture of aluminum sulfate (papermaker’s alum) and sulfuric acid |
| Acidic paper making | Forming paper from stock that has a pH value usually in the range of 3.5 to 6.5, and usually in the presence of aluminum species, e.g. alum |
| Acidity | Ability of an aqueous sample to contribute hydrogen ions during a titration with base |
| Adsorption | Molecules or ions coming out of aqueous solution and remaining on a surface |
| Agglomerate | The most general term indicating that small particles come together and stick |
| Air-float clay | A type of kaolin clay products that are prepared for use by an air-sorting process to obtain particles a good size range for the application |
| AKD | Alkylketene dimer, a synthetic sizing agent in the form of an aqueous dispersion of waxy particles, useful for wet-end addition |
| Alkaline papermaking | Forming paper from stock that has a pH value in the range from about 7 to 9.5. |
| Alkalinity | Ability of an aqueous sample to contribute hydroxyl ions during a titration with acid |
| Alkyl group | Part of an organic chemical compound that is made up mainly of carbon and hydrogen atoms in the approximate ratio of two hydrogen atoms per carbon atom (-CH2-). |
| Alum | Papermakers alum, having the formula Al2(SO4)3.14H2O, an effective coagulant of negatively charge particles in suspension |
| Aluminum trihydrate | A very bright mineral having the same chemical composition as alum floc |
| Amphoteric | Containing both positive (cationic) and negative (anionic) charged groups in a single molecule |
| Amylopectin | The branched-chain form of natural starch molecules, making up almost 100% of starch from waxy maize, a hybrid corn |
| Amylose | The linear-chain form of natural starch molecules present in the most widely used form of corn, and also in potato and tapioca starch |
| Anatase | A crystalline form of titanium dioxide having the second-highest refractive index of commonly used fillers |
| Anionic | Having a negative charge (usually balanced by counter-ions in the adjacent solution) |
| Anionic trash | Informal term meaning negatively charged colloidal and dissolved polymeric materials in paper furnish, usually coming from the wood |
| Antichlors | Additives such as sodium sulfite or hydrosulfite that reduce chlorine or related oxidants so that they do not attack wet-strength agents |
| Antifoam | A defoamer product that has been formulated with the aim of preventing the formation of visible foam, not killing existing visible foam |
| Apparent density | The mass of a sample of paper per unit area, divided by its thickness, as measured by smooth platens at a defined pressure, usually in a stack of sheets |
| Approach flow | The part of a paper machine, including the pressure screens and intake manifold, just before the thin stock reaches the headbox |
| Aragonite | A crystalline form of precipitated calcium carbonate that tends to adopt a needle-like shape, often used in coatings |
| Artificial cure | Placement of paper, taken from a paper machine, into an oven to achieve an equivalent curing effect of the same paper being stored in a hot roll of paper for many hours |
| ASA | Alkenylsuccinic anhydride, a synthetic sizing agent that usually is emulsified with cationic starch just before addition to a paper machine wet end |
| Ash content | The amount of filler in paper, as determined by incineration (which can dehydrate the filler or convert it into a different chemical form) |
| Auxo-chromes | Chemical substituent groups on dye molecules that have the effect of changing the hue |
| Barrier chemistry | A very dilute spray of high-charge, water-loving cationic polymer, sometimes with a surfactant, continuously applied to a forming fabric or roll |
| Basic dyes | Colorant molecules that have a positive charge due to amine groups and have a strong affinity for the surfaces of high-yield fibers |
| Bentonite | An informal term for “montmorillonite”, a platy microparticle product often used in sequential addition with cationic PAM for retention and drainage and sometimes also for pitch control |
| Biocides | Chemical additives designed to kill slime-forming bacteria or fungi |
| Bleedfast-ness | The ability of a dye to remain attached to fibers in paper even when exposed to fluids or to sweaty hands |
| Boil-out | The occasional cleaning of a paper machine system, during a shut-down, by filling the system with a hot solution the usually contains detergent and either NaOH, an acid, or an enzyme |
| Breaking length | A measure of the tensile strength of paper; in theory, the maximum length of a strip of paper that can support itself without tensile failure |
| Breaks of the web | Ripping of the paper as it is in the process of being made, resulting in lost production |
| Bridging | A mechanism of action of very-high-mass retention aid polymers, in which the molecules attach simultaneously onto two surfaces |
| Brightness | The diffuse reflectivity of paper at a mean wavelength of light of 457 nm |
| Britt jar | The Dynamic Drainage/Retention Jar apparatus to evaluation effectiveness of retention aids by measuring the solids in filtrate passing through a screen in the absence of fiber mat formation |
| Broke | Paper trim or reject material from the paper machine or other paper mill operations that is repulped and used again to make paper |
| Brown-stock washers | Cylinder-type vat washers (usually) for removal of black liquor from unbleached kraft pulp |
| Buffer | A system of weak acid(s) or base(s) dissolved in water that tends to hold the pH near to a constant value when acid or base are added |
| Bulk | The reciprocal of apparent density |
| Calcined clay | A product that results from heating of ordinary clay in a furnace, making it white and bulky |
| Calcite | The most common crystalline form of calcium carbonate, including almost all ground calcium carbonate and most PCC products |
| Calcium carbonate | A white mineral filler, tending buffer the pH in the alkaline range, that is available as ground limestone (GCC) and in various shapes as precipitated calcium carbonate (PCC) |
| Calcium oxalate | A type of scale that forms when oxalate (a byproduct of bleaching) encounters hard water |
| Caliper | Paper thickness, determined by measuring the distance between smooth, flat plates at a defined pressure |
| Carboxyl group | The -COOH functional group, common on fiber surfaces, that dissociates to form a negative charge, especially at pH>4 |
| Carry-over | Substances released from fibers during pulping that fail to be removed during washing |
| Cationic | Having a positive charge (usually balanced by counter-ions in the adjacent solution) |
| Cationic demand | The amount of positively charged polymer needed to titrate a given aqueous suspension of fibers or colloidal matter to zero zeta potential |
| Cationic direct dyes | ye molecules that are similar to “normal” direct dyes (large and flat), but have positively charged amine groups |
| Cationic starch | The most widely used dry-strength chemical for paper machine wet-end addition |
| Caustic soda | Sodium hydroxide, a strong base, used in pH adjustment and in broke repulping |
| Cellulose | Chain-like molecules based on sugar units, having a water-loving nature and strong tendency to form crystalline domains |
| Charge demand | The amount of a standard, highly charged polymer required to neutralize the net electrical charges on suspended matter or colloids in an aqueous sample |
| Charge neutralization | A mechanism of increasing fine particle retention (slightly) by reducing or eliminating like-charge repulsion between solids |
| Charged patch | A mechanism of agglomeration of suspended particles based on adsorption of large, oppositely charged polymers, with the effect maximized at approximately 50% coverage |
| Chalk | A calcium carbonate filler comprised of shells of marine organisms (cocoliths) |
| Chelating agents | Molecules having multiple carboxyl groups in close proximity, such that they form very strong complexes with certain metal ions |
| Chromatography | A chemical analysis method based on the different rates at which different chemicals pass through a column |
| Chromophore | A chemical group having the characteristic of absorbing visible light, usually due to the presence of long alternating sequences of double and single carbon-carbon bonds (conjugation) |
| Clay | A platy mineral filler composed of aluminum silicate, formally known as kaolinite (except that other minerals, such as montmorillonite, also can be called “clays”) |
| Cleaners | Hydrocyclone equipment designed to remove grit from thin-stock furnish by a centrifugal action of rotating liquid |
| Closed water system | A papermaking process in which the amount of liquid effluent has been decreased, sometimes to zero (totally closed) |
| COF | Coefficient of friction, the ratio of force required to initiate (static) or sustain (dynamic) sliding, versus the perpendicular force pushing the surfaces together |
| Colloidal | Having to do with finely divided substances in which at least one dimension is within the range of about 0.001 to 1 micrometers |
| Colloidal silica | A type of microparticle product that is usually used in sequential addition with either cationic starch or a PAM retention aid product to achieve enhanced dewatering and retention |
| Complexation | 1. Interaction between small molecules (ligands) and an ion to form a chemical complex. 2. Interaction between a soluble polymer and something else to form a polyelectrolyte complex that may precipitate |
| Colloidal titration | A method of determining the charge demand of an aqueous sample by addition highly charged polymer to a neutral endpoint, usually with a charge-sensitive dye endpoint |
| Conductivity | Ease with which an aqueous solution conducts electricity; conductivity increases with salt, acid, or base concentrations |
| Consistency | The mass fraction (or percentage) of solid, filterable material in a given slurry sample |
| Contact angle | The angle, drawn through the liquid phase, between a flat solid and an air-liquid interface when a drop is placed on a surface |
| Converting | Processes involved with changing paper into end-products such as cut-size paper, envelopes, boxes, etc. |
| Coordination | The meta-stable or stable association of small molecules or ions (ligands) with an ion in solution (chemical complexation) |
| Copolymer | A long-chain molecule composed of two different types of monomer units |
| Couch roll | A roll that applies vacuum through a forming fabric, by means of perforations, just before paper leaves the forming section |
| Counter-ion | Ion in solution adjacent to a charged surface, so that the net charge of the system is zero |
| Covalent | A type of strong molecular bonding that involves sharing of electrons by different atoms |
| Crosslinking | The formation of covalent chemical bonds between and within long-chain molecules, usually insolubilizing a resin in a bonded area |
| Crystal modifier | An additive that tends to make scale deposits weaker or less able to adhere to surfaces |
| CTMP | Chemi-thermomechanical pulp, a type of high-yield fiber that contributes bulk to paper |
| Curing | Reactions of certain sizing agents and wet-strength agents that occur during the drying of paper |
| DCS | Dissolved and colloidal substances, usually derived from wood and usually having a negative charge, tending to interfere with retention aids and other papermaking additives |
| Deculator | A device that removes entrained and dissolved air from thin-stock furnish by applying vacuum as the stock is sprayed into an open chamber, usually at the outlet of hydrocyclone cleaners |
| Defoamer | An additive mixture, usually containing a water-insoluble surfactant and often containing hydrophobic particles, that destabilizes foam bubbles |
| Delaminated clay | A kaolin product formed by processing in a ball mill, rubbing the clay between small porcelain spheres, separating them into thin platelets |
| Deposits | Accumulations of material, coming from the water or suspended particles, onto wetted surfaces within a paper machine system |
| Derivative | A chemical product that is formed by modification of a base material, as in the case of cationic starch made from natural starch |
| Detackifier | A mineral (e.g. talc) or polymer having the ability to adsorb onto tacky materials and reduce their tendency to adhere |
| DIP | De-inked pulp, wastepaper from which ink has been floated, screened, or washed |
| Direct dyes | Dye molecules that are sufficiently large and planar that they tend to remain on a fiber surface without need of a fixative |
| Directionality | Dependency of a given paper property on the orientation of the sample, especially in relation to the direction of manufacture (machine direction) |
| Dirt | Visible blemishes, different in color from the paper, especially when they are dark and numerous |
| Dispersants | Substances such as phosphates or acrylates that cause finely divided particles to come apart and remain separate from each other in suspension. |
| Dispersed rosin size | Rosin or fortified rosin acid that has been emulsified at high temperature and cooled |
| Dissociation | The separation of a molecule into two parts, often with one of the parts having a negative charge (anionic) and the other positive |
| Dissolved air | Molecules of nitrogen, oxygen, CO2, and other gases that are part of the liquid phase |
| Drainage | The ease with which water is released from among fibers during the formation of paper |
| Dry strength | The force or energy required to break a paper sample, by one of various procedures, after equilibration in a standard atmosphere |
| Dye | A chemical compound having the ability to absorb visible light over a certain range of wavelengths so that the diffusely reflected light appears colored |
| EBS | Ethylene-bis-stearamide, a common component of pulp mill defoamers that often is found in deposits in paper machine systems |
| Electrolytes | Molecules that develop a charge when placed in solution (ions) |
| Electrophoretic mobility | The ratio of velocity to field strength when charged particles in suspension are placed in a known electric field |
| Emulsion | Small droplets of liquid suspended in another liquid, usually with a stabilizing chemical |
| Entrained air | Bubbles that are of intermediate size so that they are carried along with the fibers in a flowing stream of papermaking stock |
| Enzyme | A protein that has the ability to direct or catalyze a chemical reaction |
| Equilibria | Rapid transformations between two or more chemical forms, the rates of which determine the ratios of the concentrations |
| Exhaustion | The process of dye material coming out of solution and remaining on fiber surfaces |
| Extended rosin size | A liquid sizing agent based on saponified rosin, to which urea has been added |
| Extractives | Low-molecular-mass materials in wood, including pitch |
| Fan pump | A very large centrifugal pump, usually in the basement below a paper machine, that may dilute thick stock with white water and/or send thin stock to the headbox |
| Fastness | Resistance of a dyed material (e.g. paper) toward either light or fluids |
| Fatty acids | Component of wood pitch having a long, alkyl group and a carboxyl group |
| Feathering | The tendency of ink to spread out in an irregular pattern due to wicking and/or an insufficient level of sizing agents in paper |
| Felt filling | Undesirable accumulation of particulate matter within the void spaces of press felts |
| Fibrils | Hair-like projections from a fiber surface, usually resulting from refining |
| Fine paper | Paper formed from bleached, generally low-yield pulp, and usually containing filler |
| Fines | Solid particles, often derived from wood, small enough to pass through either a forming fabric, a 200-mesh screen, or a 76 um hole |
| Fillers | Inorganic solid particles, usually in the size range of 0.2 to 5 micro-meters, and often comprised of CaCO3, clay, or titania |
| First-pass retention | The difference between headbox and traywater consistency, all divided by the headbox consistency |
| Fixative | An additive having the tendency to help retain dye material on fiber surfaces, usually because of a strong positive charge |
| Flocculation | A tendency for fibers to collect together in bunches in the presence of flow, and especially in the presence of retention aids; the same word also refers to the action of high-mass polymers in forming bridges between suspended colloidal particles, causing strong, relatively irreversible agglomeration |
| Fluorescent | A property of some materials to absorb light of a lower wavelength, convert some of the energy to heat, and emit light of a longer wavelength |
| Fluorescent whitening agent | A dye material that absorbs ultraviolet light and re-emits light in the blue region. Similar to an anionic direct dye in structure. |
| Foil | An informal term for “hydrofoil,” a stationary device upon which a forming fabric rests, causing vacuum and pressure pulses as the wet paper sheet passes over it, tending to enhance dewatering |
| Formation | In common speech, the word most often means “uniformity of paper” on a scale of 0.5 to 20 mm. |
| Forming fabric | The endless, moving screen upon which a sheet of paper is formed and dewatered |
| Fortified rosin size | A major component of most rosin size products, produced by reacting the levopimeric acid component of rosin with maleic anhydride |
| Freeness | The ease with which paper stock releases water during a standard test by gravity |
| FTIR | Fourier-transform infrared spectroscopy, an excellent way to determine what materials are present in a deposit sample (qualitative) |
| Fugitive sizing | A tendency of certain paper samples to temporarily loose their water-resistant properties |
| Furnish | A mixture of cellulosic fibers, optional fillers, and water from which paper is made |
| Gloss | The ability of paper to reflect some portion of the incident light at the mirror angle |
| Graniting | Uneven staining of fibers in pulp, usually due to a very high affinity of dye for fiber, together with insufficient dilution and/or poor mixing |
| Guar gum | A natural polymer that has been used as a dry-strength additive, often as a cationic derivative |
| Hardness | The concentration of alkaline-earth ions, mainly Ca2+ and Mg2+ in water, which can contribute to deposits, hurt rosin sizing, and help certain dyes adsorb |
| Hard sizing | Strong resistance of paper to penetration by water or other fluid, over a long time |
| Hemicellulose | Component of wood comprised of relatively short, slightly branched or irregular chains of sugar units, yielding increased swelling ability |
| HST | A widely used test of resistance to penetration of an acidic water solution through paper. Results are given as the seconds required for reflectance of the un-exposed side of the sheet to decrease to 80% of its initial value |
| Hydration | Reaction with water molecules or swelling in the presence of water |
| Hydrolysis | Reaction with water molecules (sometimes accelerated by acid or base) resulting in breakage of a chemical bond |
| Hydrolyzate | The breakdown product of a reactive sizing agent, leading to a net decrease in efficiency and possible deposit problems |
| Hydrogen bond | A medium-strength, directional attraction between oxygen atoms (and some others) with hydrogen atoms bonded to other oxygens |
| Hydrophobic | Water-hating |
| Hydrophile | Something that loves the water phase, often due to the presence of oxygen atoms or charged chemical groups |
| Inorganic | Not mainly comprised of carbon, hydrogen, and oxygen |
| Interfering substance | Something in the aqueous mixture that interferes with the function of papermaking additives such as retention aids, sizing agents, strength agents, etc. |
| Internal bonding | A measure of the energy required to delaminate paper (failure in plane of the sheet) |
| Internal sizing | Addition of hydrophobizing materials (sizing agents) at the wet end of a paper machine |
| Inversion of an emulsion | Dilution and agitation of a water-in-oil emulsion under conditions that change it to an oil-in-water emulsion, as in makedown of certain retention aid emulsion products |
| Ion | A molecule or atom in solution that has at least one positive or negative electrical charge |
| Jet cooking | Exposing a suspension (usually of starch granules) to high temperature under elevated pressure |
| Kaolin | Another word for clay, a platy aluminum silicate mineral that is used as a white filler |
| Lattice substitution | A mechanism whereby crystalline substances can have a charged character, when an occasional atom having a different valence takes the place of the atom that usually occupies a certain position in the crystal |
| Light absorption | An ability of many substances to convert light energy into heat, resulting in less reflected light and often producing a color effect |
| Lignin | Three-dimensional, natural phenolic resin that binds fibers together in wood |
| Lipophile | Something that loves oil, usually due to a predominance of alkyl or aromatic groups |
| Lumen | Central space within a wood fiber that may collapse during refining and drying of paper |
| Machine chest | Usually the last large tank that contains thick-stock pulp before it is made into paper |
| Makedown | Diluting and agitating a concentrated additive or powder so that it is ready to pump to the paper machine |
| Marangoni effect | A tendency of foam bubbles to be flexible and to repair themselves after they are squeezed |
| Micro-particles | Particulate additives used for retention and drainage promotion, characterized by having very high surface area and negative charge |
| Middle lamella | Area between fibers in wood that is filled with lignin, a natural, phenolic “glue” |
| Monomer | A non-polymeric chemical entity, i.e. a single unit |
| Multi-valent | Having two or more electrical charges per molecule (ion); for example, soluble aluminum forms the trivalent Al3+ ion at low pH |
| Neutralization | The addition of just the right amount of material having an opposite charge to achieve a zero surface (or “colloidal”) charge on suspended matter in an aqueous sample |
| Non-process elements | Materials dissolved in process water that tend to circulate around the system and not become part of the paper product |
| Olation | Formation of bonds between aluminum atoms in aqueous solution, involving OH groups as the bridges (a step in polymerization) |
| Online | An operation or measurement that occurs automatically and continuously during an industrial process |
| Opacity | Ability of paper to hide things such as print images on subsequent sheets or printed on the back |
| Optical brightener | An informal term for “fluorescent whitening agent,” a dye material that absorbs ultraviolet light and re-emits light in the blue region |
| Osmotic pressure | A tendency for soluble materials to flow across a barrier in whatever direction will achieve more nearly equal ionic strength on each side |
| Over-cationized | A papermaking system to which so much cationic material has been added that the zeta potential is reversed to strongly positive |
| Oxidants | Chemicals that tend to convert alcohol groups to carboxylic acid groups. Oxidants are used for bleaching and as part of biocide treatments |
| Oxolation | Conversion of the olated form of aluminum polymers to Al-O-Al bonds, usually involving the application of heat during drying of paper |
| PAC, poly-aluminum chloride | A cationic flocculant solution formed by partial neutralization of aluminum chloride’s acidity |
| PAM, poly-acrylamide | Very-high mass copolymers or acrylamide and other monomers, used as retention aids |
| Parenchyma | Cells within a tree that are two small to be considered fibers, often used to store food |
| Passivation | Continuously spraying a barrier chemical or release agent onto a forming fabric or other equipment to prevent deposits of tacky materials |
| Paste rosin size | A sizing agent mixture of rosin free acid and saponified rosin, no longer in common use |
| PCC | Precipitated calcium carbonate, a bright filler having a variety of possible shapes and sizes |
| PEI, poly-ethylenimine | A class of very highly charged cationic polymers, usually highly branched, useful for charge control and drainage promotion, especially under acidic to neutral conditions |
| PEO, poly-ethylene oxide | A very-high-mass, non-ionic retention aid that usually requires sequential addition of a phenolic cofactor (or lignin) |
| Permanent wet strength | Wet strength that does not depend on the time duration of immersion, once wetting is complete |
| pH | Negative logarithm (base 10) of the hydrogen ion concentration, a factor related to the acidity of an aqueous solution |
| Phenolic | Having to do with aromatic (benzene) rings connected to an OH group, as in lignins |
| Pigment | Finely divided particulate matter that is mainly intended to affect optical properties of a product (see filler) |
| Pinholes | Small holes in paper, often caused by entrained air bubbles, where it is possible to see light through the sheet |
| Pitch | Wood extractives, in the context of tacky deposits onto papermaking equipment or spots in the product |
| Plate counts | A common test to estimate the concentration of free-floating biological cells, by greatly diluting the sample and spreading the diluted sample on top of some growth medium, and later counting the colonies of cells |
| Polarization | A method of light microscopy that uses light waves that are oriented in the same plane |
| Polyamine | A highly charged cationic polymer, often used for charge control or as a pretreatment before certain retention aid treatments |
| Poly-DADMAC | Poly-diallyldimethylammonium chloride, a fully-charged, cationic polymer often used as the standard for cationic demand titrations |
| Polymer | A very large molecule comprised of one or more types of repeating units |
| Polysaccharides | Large molecules composed for sugar-type units, e.g. cellulose, starch, and hemicellulose |
| Post-consumer waste | Paper that has been printed or converted, distributed to end-users, and collected from consumers as waste paper |
| Precipitate | Insoluble materials in a mixture formed as a result of interaction between soluble components, often resulting in turbidity or settling of the solid material |
| Primary fines | Fines derived from structures present in wood and released after kraft pulping, before refining |
| Primary wall | The lignin-rich outer wall of a papermaking fiber that is mostly removed by kraft pulping |
| Protection | A hypothetical mechanism to explain wet-strength effects as due to the chemical blocking of access to inter-fiber hydrogen bonds |
| PVSK | The potassium salt of polyvinyl chloride, a highly charged, negative linear polymer often used in charge titrations |
| Ray cells | Cellulosic structures within a tree, smaller than fibers, that conduct water and nutrients in a radial direction |
| Reactive size | A sizing agent such as ASA or AKD that undergoes a covalent reaction when heated in the presence of fibers |
| Refining | Passing pulp through a device that applies compression and shear forces onto the wetted fibers, causing fibrillation and increased flexibility |
| Reinforcement | A hypothetical mechanism to explain wet-strength effects as due to formation of covalent bonds, adding to the effects of hydrogen bonds |
| Repulping | Transforming waste paper back into fibers by immersion in water and strong mixing |
| Resin acids | Component of softwood pitch having a ring structure; also used to make rosin size |
| Restabilization | The result of adding too much low-mass cationic additive to furnish, such that all the surfaces become positive and repel each other |
| Retention | The efficiency with which small particles (or additives) remain in the paper during its formation rather than staying with the white water |
| Retention aids | Chemical additives, especially high-mass copolymers of acrylamide, designed to increase the retention efficiency of fine materials during paper formation |
| Rhombohedral | A form of precipitated calcium carbonate in which the particles are relatively “blocky” |
| Rosin acid | A mixture of water-insoluble carboxylic acids from conifers, mostly in the form of multi-ring compounds, in their protonated form |
| Rosin size | Various products, derived from certain wood extractives, that can be added at the wet end in the presence of aluminum species to make paper resist water penetration after it has been dried |
| Rutile | A form of titanium dioxide having the highest refractive index of commonly used fillers |
| S2 sublayer | Most massive component layer of a woody fiber, having cellulose molecules almost aligned with the fiber |
| Salts | Inorganic substances that dissociate into ions, raising the electrical conductivity of solution but do not make the solution acidic or alkaline |
| Saponifyable | Capable of being formed into a carboxylic acid soap upon addition of base (e.g. esters, and the protonated form of carboxylic acids) |
| Save-all | A device, usually based on disc screens, a screen cylinder, or floatation, that collects fine materials from white water so that they can be returned to the papermaking process |
| SBR | Styrene-butadiene resin, a very common latex binder used in aqueous coating formulations |
| Scale | Hard deposits on wetted papermaking equipment, usually comprised of inorganic compounds such as barium sulfate |
| Scalenohedral | A rosette shape of certain precipitated calcium carbonateparticles that confer bulk and opacity to the paper |
| Screen(s) | Device(s) to remove large solids such as fiber bundles and flakes from thin stock just before the headbox of a paper machine |
| Secondary fines | Fines torn from fiber surfaces or resulting from fiber breakage during refining |
| Shear | A change in velocity with respect to distance perpendicular to the direction of flow |
| Size press | Equipment for applying a polymeric solution to the surface of paper just after it has been dried for the first time, usually by means of a puddle and nip between rolls or by metering the solution onto a rubber roll |
| Size reversion | A tendency for certain types of sized paper to gradually loose their water-resistant nature |
| Sizing | 1. “Internal” sizing is treatment of the fiber slurry so that the paper will resist fluids. 2. “Surface sizing” is addition of a film of starch solution or other material at the paper surface. |
| Slime | A slippery deposit composed of bacteria or fungal cells |
| Slip | A condition of low friction coefficient – either sheet-to-sheet or sheet-to-equipment, often attributable to waxy materials or high AKD size addition level |
| Slip plane | The hydrodynamic slip plane is an imaginary plane about 2-10 nm from a charged surface where ions closer to the surface act as if they are part of the surface and those outside act as if they are part of the surrounding aqueous solution |
| Soap sizing | Achieving resistance to water penetration by adding the sodium salt of rosin at the wet end |
| Species | The form or forms that a chemical may take when equilibrating with an aqueous solution, e.g. Al3+ as an example of an alum species at low pH |
| Specific surface area | The surface area of a sample of solid material, divided by its mass |
| Spreading | A time-dependent increase in wetted area when liquid is placed on a solid such as paper |
| Spreading coefficient | A thermodynamic parameter that can be used to predict the best composition for a defoamer |
| Stable suspension | A mixture of finely divided particles in a liquid in which the repulsive forces, due to like charges and/or adsorbed molecules having long fluid-loving tails extending into the fluid, prevent sticking collisions |
| Starch | A natural product from corn, potatoes, tapioca, etc., and used for dry strength. Cationic starch solution is added at the paper machine wet end. Various forms of dissolved starch are added at the size press. |
| Stickies | Sticky materials in recycled papermaking pulp, often involving pressure-sensitive labels |
| Streaming current | A method for estimating the charge demand of an aqueous sample by adding titrant to a device with a loose-fitting plastic piston reciprocating in a plastic cylinder fitted with two electrodes and a detection system |
| Streaming potential | A method for estimating the relative magnitude of zeta potential at fiber surfaces by forcing aqueous solution through a mat or plug of fibers and noting how the electrical potential measured across the mat changes with applied pressure |
| Stuff box | An overflow chamber that provides a constant hydrostatic head before the stock pump that meters thick stock to a paper machine |
| Sulfate reducing bacteria | A type of bacteria that thrives in oxygen-free (anaerobic) environments, causing odors and corrosion of stainless steel |
| Surface sizing | Application of a solution, often containing starch, to the surface of paper, usually in order to increase surface strength, and sometimes with addition of hydrophobic polymers |
| Surface tension | The strength of the tendency of a liquid to adopt a shape having the minimum surface area (often forming a droplet) |
| Surfactant | A surface active agent, usually comprised of molecules with water-loving and water-hating groups, used for wetting, emulsifying, etc. |
| Synthetic sizes | Alkenylsuccinic anhydride (ASA) and alkylketene dimer (AKD) hydrophobizing agents for wet-end addition |
| Talc | A very soft, platy, oil-loving mineral product used as a filler and also used (in finely divided form) for pitch control |
| Temporary wet strength | Increased strength of treated paper, tested after initial, complete wetting, which decays within a few minutes or hours |
| Thermo-setting | Tending to become a permanently cross-linked, insoluble solid when heated |
| Titration | Gradual addition of a known solution (titrant) of known concentration until an endpoint is reached |
| Thick stock | A mixture of papermaking pulp and other materials with a consistency of about 2 to 5% |
| Thin stock | A mixture of papermaking pulp and other materials, after having been diluted with whitewater at a fan pump |
| TMP | Thermomechanical pulp, a high-yield pulp produced in a refiner |
| Titanium dioxide | A white mineral filler having a high refractive index, making it effective for increasing the opacity of paper |
| Tracheid | The “fiber” of a softwood or conifer tree |
| Tray water | Process water, containing fine materials, that drains from paper during its formation (a synonym for “cloudy white water”) |
| Triglycerides | Components of wood pitch consisting of three fatty acid moieties attached to glycerine by ester bonds |
| Trim addition | Addition of a portion of a certain papermaking additive to thin stock, after base-loading some to thick stock, to enable more rapid process control |
| Turbidity | A measure of the ability of an aqueous sample to scatter light, indicating the relative amount of fine, suspended materials |
| Turbulence | The existence of a chaotic mixture of overlapping eddy currents of flow |
| Two-sidedness | The existence of differences in appearance or other properties of the two sides of paper |
| Unsaponifiable | Not capable of being formed into a carboxylic acid soap upon addition of base (e.g. not esters, not carboxylic acids |
| Venturi | A device that entrains material into a fluid stream by taking advantage of the vacuum created by an expansion in the flow pattern |
| Vessels | Structures within hardwood (deciduous) trees that conduct water from the roots up the tree |
| Viscosity | The tendency of a liquid to resist flow; e.g. syrup has a higher viscosity than water |
| Wall | The substance of a fiber between its outside and its lumen (interior space) |
| Washing of pulp | Removal of pulping or bleaching liquors from cellulosic fibers either by (a) dewatering, then diluting with “clean” white water, or (b) displacement of the liquor by spraying wash water onto a mat of fibers |
| Waxes | Water-hating natural solid-like substances in wood, rich in alkyl (-CH2-CH2-) groups |
| Weak acid | A substance that only partly dissociates into hydrogen ions and a conjugate base upon addition to water |
| Wet chemistry | An informal term, meaning the type of chemical test that can be performed by adding a solution to a sample to be analyzed and observing a color change, etc. |
| Wet end of a paper machine | Roughly speaking, the parts of a papermaking process between pulping (or bleaching) and wet-pressing of the paper |
| Wet web strength | The strength of a wet sheet of paper after its formation but before it has ever been dried |
| Wet-strength | The strength of a sheet of paper after it has been exposed to a standard solution for a standard length of time, but often expressed as a ratio vs. the dry strength |
| Wettability | The relative ease with which a certain solid surface accepts liquids, usually defined in terms of the angle of contact of a flat solid with an air-liquid interface |
| Whiteness | A subjective impression of white appearance, usually favoring a bluish tint |
| White pitch | Deposits on papermaking equipment, a major component of which is latex binder from coated paper or broke |
| White water | Process water within a paper machine system, especially referring to water that is drained from paper as the sheet is being formed |
| Wire | Informal synonym for forming fabric, the continuous screen on which paper is formed |
| X-ray fluorescence | An analytical method for determination of the ratio of different metal ions in an ash sample |
| Yield of paper pulp | The ratio of pulp solid mass to the solid mass of the original wood that it was derived from. High-yield pulps are produced by mechanical refining or grinding. Kraft pulps are relatively “low yield”. |
| Z-direction | The direction perpendicular to the plane of a sheet of paper |
| Zeta potential | The average electrical potential near to the surfaces of particles or fibers suspended in water, evaluated by a method involving relative motion of the solids versus the liquid |