Mini-Encyclopedia of Papermaking Wet-End Chemistry

GLOSSARY: Short Definitions and Some Links to More Information

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 platey 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 Dye 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 neu-tralization A mechanism of increasing fine particle retention (slightly) by reducing or eliminating like-charge repulsion between solids
Charge 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 platey 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)
Coagulation The coming together and sticking of small, suspended particles, brought about by addition of salt, change of pH, or chemical additions that reduce or eliminate like-charge repulsion
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 insolubizing 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
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 bond 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 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 platey 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 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 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 part 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 carbonate particles 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 is added at the paper machine wet end.
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, platey, 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
Termo-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
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 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

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