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Paper & Pulp Dictionary Glossary "S"

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 Definitions for commonly used terms, words and phrases used in the pulp and paper trade



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The term is used interchangeably with the word "bag" applied to a non-rigid container made from paper or other flexible material.
Safety Paper
Papers with a special protection against abusive imitation. The safeguards used during the production of the paper - some of them chemicals are secret.
Salt Cake
Or sodium sulfate added to the black liquor to compensate for the soda loss.
Sanitary Papers
The group of sanitary papers includes cellulose wadding, tissue and crepe paper, made from waste paper and/or chemical pulp - also with admixtures of mechanical pulp. As a consequence of the importance of tissue today, this name is now used internationally as a collective term for sanitary papers. These grades are used to make toilet paper and numerous other sanitary products such as handkerchiefs, kitchen wipes, towels and cosmetic tissues.
Sanitary Tissue Paper
Tissue is a sanitary paper made from chemical or waste paper pulp, sometimes with the admixture of mechanical pulp. It has a closed structure and is only slightly creped. It is so thin that it is hardly used in a single layer. Depending on the requirements the number of layers is multiplied. Creping is made at a dryness content of more than 90 %. The dry creping (unlike with sanitary crepe papers) and the low grammage of a single tissue layer result in a high softness of the tissue products. For consumer products it is normally combined in two or more layers. The flexible and highly absorbent product [is mainly produced from chemical pulp and/or DIP - sometimes also with admixture of groundwood pulp] can also be provided with wet strength. Applications: facial tissues, paper handkerchiefs, napkins, kitchen rolls, paper towels, toilet paper.
Sap Wood 
The fluid part of the tree that moves up from the roots through the outer portion of the trunk and branches and contributes to its growth.
Satin Finish
A smooth, satin-like, semi-glossy finish of paper or Bristol.
Equipment used to reclaim fibers from white water.
Saw Dust
Fine wood particles created when sawing wood; used as biofuel, pulping raw material, panel board production, animal litter etc.
To impress or indent a mark with a string or rule in the paper to make folding easier.
To impress or indent a mark with a string or rule in the paper to make folding easier.
Scott Bond
An internal bond test that measures the force needed to separate fibers within a single ply by TAPPI method.
Device used to remove large solids particles such as fiber bundles and flakes from stock. In good old days screen used to be open type and could deal with thin stock only. Modern screen are closed (pressurized) and can handle low, medium and even high consistency stock. Perforation in screen basket can be circular, counter shrink or slotted. The screen used just before headbox not only remove large particles but also align fibers in the direction of stock flow.
Scuff Resistance
Linerboard's ability to resist abrasion in the shipping environment may affect external appearance.
The means of joining the two ends of the fabric together.
Secondary Fibers
Fibers recovered from waste paper and utilized in making paper or paperboard.
Security paper
Paper which includes identification features such as metallic strips and watermarks to assist in detecting fraud and to prevent counterfeiting.
Self Adhesive paper
Used essentially for labeling purposes, this grade has a self-adhesive coating on one side and a surface suitable for printing on the other. The adhesive is protected by a laminate which enables the sheet to be fed through printers or printing machines, the laminate subsequently being stripped when the label is applied
Semi-Alkaline Pulp (SAP)
Sulfite pulp cooked at slightly alkaline pH (normal sulfite pulp is cooked at acid pH). SAP is superior in strength to normal sulfite pulp. Used mainly in printing papers.
Semi-Bleached Pulp
Pulp bleached to a brightness somewhere between that of unbleached and fully bleached pulp.
Semi-chemical Pulp
Pulp produced by chemical treatment followed by mechanical treatment.
A number of units or bales picked up at the same time by crane or truck.
The color depth and hue in comparison to papers that are the same color; also used to describe the color achieved by adding dye to pulp slurry. There is a wide shade variety in white papers, as well as in colored papers.
Shadow Mark
A defect in paper appearance which looks like the drilling pattern in a suction roll. It is due to opacity effects caused by areas of vacuum and pressure as the wet web passes over a suction roll.
The device to shake the wire at the breast roll end from side to side.
Sheffield Porosity
A test used to measure the smoothness of paper by measuring the rate of air flow over the surface of the sheet. The lower the number, the smoother the sheet.
Sheeter or Cutter
Machine for cutting the paper web into sheets.
Small bundles of fibers that have not been separated completely during pulping.

Show Through
The degree to which a printed film is visible through paper due to the low opacity of the paper.
The undesirable condition in which the printing on the reverse side of a sheet can be seen through the sheet under normal lighting conditions. The more opaque a sheet, the less the show-through.
Water jets or sprays used throughout the pulp and paper mills to wash wire mesh screen, forming wires, press felts, pulp mat, to dilute pulp etc.
High Pressure Showers A shower consisting of numerous needle jet nozzles along its length at a pressure of up to 300 psi.
Lubrication Showers A shower consisting of fan nozzles along its length to provide full coverage of the felts surface with water. This lubricates the felt as it passes over the suction boxes.
Oscillation Showers The movement from side to side of the shower bar to ensure full coverage of the felts surface by the water jets.
Side Run

(1) A narrow reel removed from a web during processing, the width of which is less than the size ordered, but is large enough to permit its use for purposes other than re-pulping.

(2) An additional part of an order placed in order to better utilize the maximum trimmed machine width of the making machine.

Size Press
Section of paper machine where surface treatments are applied to the sheet of paper to give it special qualities. Normally comprised of a pair of rolls towards the end of the dryer train between which the dry or partially dry web is passed, and into the nip of which a liquid, usually starch, is applied to impart strength to the sheet. Sometimes a chemical may be added to produce a water-resistant sheet
Sized Paper
Sizing reduces the water absorbency of the paper and thus creates the condition for the writability with ink. Sized paper is also used for many other purposes (printing, coating, gluing, etc.), and the sizing agents must fulfill a wide range of tasks. For instance, they control the water absorbency and increase the ability to retain water and ink (pick resistance).
The treatment of paper which gives it resistance to the penetration of liquids (particularly water) or vapors. Sizing improves ink holdout.
Outlet from the head box through which the pulp suspension is fed into the forming section.
Slide Resistance
The ability of containers to resist sliding in unit loads can be predicted for the coefficient of friction of the combined board. A low coefficient demonstrates containers slipping from the load.
Fungus or other bacteriological growth. If not controlled in papermaking system, may cause process and quality problems.
Slime Holes
A hole in paper, characterized by brownish translucent material around the edges. Caused by a lump of slime which has formed in stock system from the growth microorganisms, then becoming detached and flowing onto the paper machine wire with the fiber to form a non-fibrous area.
Rotary knife used to slit or trim a paper web into specified width.
Dividing a web of paper in the lengthwise direction into two or more narrower webs.
Measure of pulp drainage. Has an inverse relationship to freeness.
The waste material left over after pulping and deinking. Although some sludge is produced in the virgin papermaking process, far more is produced in the deinking (recycling) process. Recycling breaks recovered paper down into fibers, which are sent to the paper machine for new production, and other materials, which drop into the sludge. These "other materials" include clay coatings, fillers from the previous paper, paper clips and staples, fibers too short to be made into paper, ink if it wasn't skimmed off in the deinking process, and any "junk" that crept into the wastepaper bales.
Inorganic chemicals obtained in molten form from the recovery furnace.
Smooth Finish
A highly calendered or machine-finished sheet.
The surface uniformity of paper. Sheets that are flat and even provide better ink dot formation and sharper images.
Soda Pulping
An alkaline pulping process that uses a simple, sulfur- free sodium hydroxide as cooking liquor.
Soft Cook
Over-cooked pulp.
Soft Nip Calendar
A machine device consisting of two or more pairs of steel and composition rolls; it is designed to achieve much of the quality of a Supercalender, with much of the production advantage of being on machine, but without the severe operating difficulties of an on-machine Supercalender.
Woods obtained from coniferous trees. Generally grown in cold climates. Softwood grows slower than hardwood but have longer fibers compared to hardwood.
Solid Fiberboard
Collective term for all solid board grades.
Specialty Paper
The group of specialty papers comprises numerous paper grades, each characterized by particular properties. These properties often require special raw materials.
Specialty Pulp
Chemical pulps used for purposes other than ordinary papermaking (e.g. in textile production)
Specific Energy (Refining)
Energy applied per unit weight on oven dry basis (KWH/MT) during refining.
Specific Surface (Fiber)
Fiber surface area per unit weight (OD basis)
Specific Surface Load (Refining)
Specific edge load divided by refiner bar width factor (Watt-Sec/m2)
A small defect of foreign substance with contrasting appearance to the surrounding paper.
Spent Liquor
Liquor recovered from cooked pulp.
Formed by overlapping webs and joining with a strip of double-faced adhesive tape. Used for lighter-weight grades of paper.
Spread Coating
A method of coating a web of paper by means of a vertical plate restraining a pond of viscous coating material, for example resins, plastics or adhesives, which is drawn through an adjustable gap between the plate and the paper by the forward movement of the web over a horizontal support
The wooden hammers used in a watermill to pulp rags in order to separate the fibers.
Standard Test Conditions
Atmospheric conditions of temperature and humidity in which laboratories agree to conduct tests, eliminating those variables in comparing results.
A natural product from corn, potatoes, tapioca, etc., and used for dry strength. Cationic starch is added at the paper machine wet end.
Starch is a free flowing white powder. Typically, starch used in the paper industry is extracted from maize kernels, wheat or potatoes; in rare cases, tapioca or rice can be the source. Starches from the different plants each have a characteristic granule size and shape.

Potato starch is often referred to as farina, and maize starch is sometimes called corn. Native starch is sometimes called pearl starch.

Steam Finishing or Steam Calendering
A way of treating paper before calendering to improve its density and surface smoothness
Wood chips are often treated with steam prior to pulping; used in thermo-mechanical pulping. Also injection of steam in direct or indirect cooking digester for chip packing and or cooking.
A sheet of plastic, paper, or other material with letters or an image cut out of it. When placed on a surface and inked, it reproduces the cut-away images onto the material behind it.
Sticky materials in recycled papermaking pulp, often resulting from pressure-sensitive labels.
The ability of paper or paperboard to resist an applied bending force and to support its own weight while being handled. A sheet that is too limp can cause feeding and transport problems in copiers and printers. An adequate degree of stiffness is important to avoid distortion of the paper due to the pull of ink during offset printing. Stiffness is critical to many converting operations for forms and envelope grades.
A term used to define pulp after mechanical (refining or beating) and /or chemical treatment (sizing, loading, dying etc.) in the paper making process. A pulp ready to make paper.
Stock Preparation
Collective term for all treatment necessary for the preparation of the stock before it reaches the paper machine.
Straw Pulp
Pulp that is made from the straw of grains such as rice straw. It is cooked by soda process.
Board made from partially cooked straw, bagasse or grass or a mixture of these.
The maximum tensile strain developed in paper before rupture. The stretch or percentage elongation is expressed as a percentage.
The penetration of ink through paper.
The base material on which a substance (such as ink, adhesive, coating) is applied.
Suction Box (Vacuum Box)
Device that removes water from the paper machine by a suction action located beneath the wire at the wet end.

Sulfate Pulping
Alkaline process of cooking pulp.
Sulfite Pulping
Acid process of cooking pulp
A stack of alternating steel and fiber-covered rolls at the end of the paper machine which is used to increase a sheet's gloss and smoothness.
Treatment of paper on an off-machine supercalender to improve smoothness and gloss.
Paper that has been treated with starch or other sizing material at the size press of the paper machine. This term is used interchangeably with the term "tub-sized", although tub-size more properly refers to surface sizing applied as a separate operation where the paper is immersed in a tub of sizing (starch or glue), after which it passes between squeeze rolls and is air dried.
Surface Roughness
For coated boards, Parker Print Surf (PPS) roughness tester is used where the test result is expressed as an average of the surface profiles in micrometers ( mm ) low results show smooth surface while high results indicate poor surface.
For coated board, Bendtsen method readings given as total leakage of air in ml/min. Smoother surface has lower readings
Surface Smoothness
The smoothness of the linerboard surface may affect printing quality because slight depressions may not receive complete ink coverage. Surface smoothness may also affect the coefficient of friction, gloss and coating absorption.
Surface Strength Test
The method consists of printing a strip of paper in a print tester at an accelerating rate. The method is preferable to Wax Pick.
An increase in volume of fiber due to the absorption of liquid.
Synthetic Fiber Paper
Papers made from synthetic fibers such as polyamide and polyester, from viscose staple fiber or sometimes also with fillers. The fibers are mainly held together by binders. The durable synthetic fiber papers are used for maps and highly important documents such as driving licenses or vehicle registration books.
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