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Packaging - Glossary - S

  • Packaging Processes

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    The Glossary of the International Trade Centre (ITC) on the technical terms used in the packaging sector is a database designed to provide updated information on the specific terminology used in the packaging industry. This Glossary is a tool placed at the disposal of users for information only. It is not designed to replace the appropriate professional advice in any way. Users are invited to submit their comments and observations by email to Mr. Frederic Couty, Senior Adviser, Export Packaging at the following email address: fcouty[at]intracen.org

    Select an alphabetic above to access the glossary.

  • S


    A small flat bag containing for example single portions of products, and generally produced by sticking two rectangular pieces of sheet or film material along their edges. See also: Pouch.


    Usually refers to a heavier duty preformed bag made of paper or other flexible material, either plastic or textile fibre. The main form of paper sack is the multi-wall sack. A multi-wall sack is constructed from several plies and made in tubular form with its ends closed by sewing or pasting. The material of the inner plies will vary with the demands of the product and can include all types of plain and coated papers, plastic films and aluminium foil. An open-mouth sack is delivered with the bottom closed. The mouth is usually closed by sewing after filling. A valve sack is fitted at one corner with an extended opening into which a filling nozzle can be inserted for loading the product. When this extension is pushed back into the sack, it acts as a self-sealing closure, a one-way valve to contain the product.


    A closing device which cannot be opened unless specific directions are followed. Used on hazardous materials and on drugs, e.g. child-proof closure.

    Sandwich printing

    The printed surface is laminated or coated to another material which protects it from damage or contact with the product. This technique is commonly used when reverse printing is employed on transparent food packaging.

    Salt-spray test

    Exposure to a spray or fog of salt solution in a specially de­signed cabinet; it provides an accelerated test of product and pack performance in maritime conditions.


    See: Polyvinylidene chloride - PVDC. SaranTM is a proprietary name for this plastic material.


    1.A machine for electronic colour separation of original multi-colour designs during the preparation of printing plates.

    2.An electronic device used to “read” the bar codes such as the U.P.C. and EAN systems of article identification.

    Scanning wand

    A hand-held device that is passed over a bar code or similar detectable symbol, to input product/pack information to an electronic data collection system.


    To make an indentation or a partial cut in a flat material for the purpose of facilitating bending, folding, creasing or tearing. Scores are made in paperboard to facilitate bending or creasing. Scores in the form of partial cuts are applied to paperboard, plastics and metals to permit tearing or opening (key-opening cans).

    Scotch tape test

    A simple but rough test for determining the permanency of printing on plastic films. A piece of cellophane adhesive tape, or other pressure-sensitive tape, is stuck to a section of printing and then pulled off in one motion to see whether or not the ink will come off with it.

    Screw cap

    A cylindrical closure having a thread on the internal surface designed to engage a compatible external thread on the finish or neck of a container.


    In printing technology, an image area broken down into printing and non-printing picture elements (halftone dots or lines) where the size and/or number of dots per unit area vary according to the tone values of the original. The two main kinds of screening are amplitude-modulated and frequency-modulated screening. Today, screening a continuous-tone original to generate a halftone image is usually accomplished electronically.

    Screen printing

    Decorating process em­ploying screen stencils. Process can be applied to any container regardless of shape or size. Method once used silk screens, hence the previous name ‘silk screening’ commonly used for this process. Now, however, the process uses stencil screens of various materials, especially fine wire mesh and is used in particular for high quality, heavy ink weight printing on irregular-shaped glass and plastic containers.

    Screw-Thread Vial

    A vial with a very short neck and an outside screw-thread finish.


    (1) An open mesh fabric used to reinforce packaging material. (2) Combined with barrier material to form a sheet.

    Scuff resistance

    The resistance of a print or coating to removal or scratching.


    In offset and similar printing processes, defects in the form of inked areas appearing outside the intended print image. This arise because surface of the image carrier is accepting ink in the wrong places or, in the case of offset printing, because the blanket or transfer cylnder has surface defects and is applying ink where it is not required.


    1.(Noun) A tight closure.

    2.(Noun) A protective device applied to a closure or container which cannot be removed without its partial or total destruction, i.e. a tamper-evident closure (seal).

    3.(Verb) To fasten or secure; to close tight.

    Sealing compound

    See: Gasket.

    Sealing tape

    A strip of cloth, paper, film, etc. coated with an adhesive, used to seal packages and containers.


    1.(Noun) A joint connecting parts of a metal or plastic container body.

    2.(Verb) To form a seam by abutting, overlapping, folding, sewing, or otherwise fastening two edges of a material.


    Without a seam or joint as applied to a plastic container or to a one-piece metal can body produced by the drawing process. A two-piece can.

    Secondary closure

    A means to secure or hold firmly in place a primary closure. Often a shrinkable band of viscose or PVC.

    Secondary packaging

    Packaging that collates, groups or wraps one or more primary packs.


    Package surface or label pre-coated with adhesive and protected until adhesion is required by a non-adhering liner material.

    Self-opening (SOS)

    A term describing a bag closure which can be opened by a simple hand movement.


    1.The property of certain adhesives to adhere to themselves on contact, even after evaporation of solvents, and when they are dry to the touch.

    2.The property of certain plastic films which permits them to seal either to themselves or to other surfaces.


    Refers to a store, shop or market where the customer selects merchandise without the aid of sales staff and brings it to a check-out cashier for payment before leaving the store.

    Semi-chemical pulp

    The raw material for paper making prepared by a combination of both mechanical and chemical fibres. Used in the production of fluting (corrugated medium).

    Serum Vial

    A vial having a neck with a relatively small opening to receive a rubber plug stopper and aluminum seal.

    Serving suggestion

    Statement on a package indicating that the illustration shows product as it can appear when served, rather than in its condition inside the pack.


    1.The form a material assumes in the transition from the fluid state to the condition of desired solidity. In adhesives, the point at which an adhesive has developed sufficient viscosity and tack to hold the surfaces together.

    2.(Verb) To harden, reach a state of being set.

    Setting time

    The time required for a material to set from the time of its application in a fluid state. See also: Open time.

    Set-up paper box

    A rigid paperboard box delivered in a ready-to-use shape, as distinguished from a folding carton which is delivered flat.


    Material, such as lumber, plywood, fibreboard, fastened to the frame of a crate across all openings, to add strength to .the crate or to prevent loss of contents, especially small parts, pilferage of, or entry of dirt, water, etc., into the contents; or fastened to the walls of a freight car to protect a load.


    The strain produced by pressure in the structure of a substance when contiguous layers are caused to shift laterally over each other, e.g. the action of scissors.

    Shear strength

    The ability of a material to withstand shear stresses.


    A rectangular piece of material (metal, plastic, paper, etc.).


    Refers to the process of feeding a printing press or printer-slotter with individual sheets of material rather than with continuous webs of material.


    The conversion of rolls of paper into sheet form with the use of sheeting equipment (called sheeters).

    Shelf life

    The length of time that the product, usually packed, will remain saleable under defined conditions of storage.


    A line of containers (used by drug and chemical customers) that was designed to give the packer specific advantages in terms of label space, maximum size, appearance and easy pouring.


    A line of stock oblong bottles, described in drug and chemical stock catalogues.


    (1) A cylindrical seamless part drawn from flat sheet metal. (2) A plain, unprinted carton designed to be overwrapped with paper. (3) Any rectangular tube open at both ends for a set-up paper box. (4) A collapsible tube de­signed for one single application of contents. Has no neck, orifice or cap, but has a shoulder which forms the closed end of the container. Designed to be opened by puncturing, tearing, breaking off a small tip, etc. Shells are also called "'one shot" or single dose or blind neck tubes. (5) The body sidewall of a drum. (6) The outer sec­tion of a fibre drum sidewall. (7) A sheet of cor­rugated or solid fibreboard scored and folded to form a joined or unjoined tube open at both ends. Used as inner packing. (8) The flat topped, threaded part of the screw cap which pulls the liner downto seal the finish of the con­tainer.

    Shell Vial

    A cylindrical container, usually made of glass, characterized by having straight sides, being neckless, and having a flat bottom. Made by sealing one end of a glass tube of appropriate diameter and length.


    Solvents leaching through a plastic container.


    A box for transporting goods. See also: Transport package.

    Shipping container (also master container or outer container)

    A container which is sufficiently strong, by reason of material, design and con­struction, to be shipped safely without further packaging either as a primary pack or as an outer container for consumer packages (interior containers). Examples: wooden boxes or crates; fibre, plywood and metal drums; corrugated and solid fibre boxes; multiwall paper shipping sacks; textile shipping bags, etc.

    Shock test

    The application of sudden forces to a filled container to determine its performance under conditions simulating those that may be encountered during shipment. See also: Vibration test.

    Short Grain

    Term used for a print sheet that has been cut from the web in such a way that the grain of the paper runs along the short side of the sheet (travel direction of the during papermaking). This holds true for other mater such as plate material for printing plates (see also long grain).


    That part of a container joining the body and the neck as on a glass bottle, tube, etc.

    Show-through (in printing)

    Defect arising from the appearance of print from the reverse side of the material , due to translucency or thinnessof the sheet.

    Shredded paper

    Usually waste paper cut into narrow strips, used as cushioning material.

    Shrink band

    A plastic sleeve which when heated, or a viscose sleeve which when dried, will clamp tightly around container surfaces, generally the neck and closure of a bottle, to provide a seal.

    Shrink film

    A film which has been oriented in one or two directions and after being wrapped around a product or package, shrinks to its original dimensions when heated and forms a tight contoured fit.

    Shrink gun

    A hot-air blower to effect the shrinkage of plastic film, wrapped, for example, around a unit load.

    Shrink label

    A plastic sleeve, usually PVC, which is printed in a distorted design and is shrunk around the body of a container by heat. The design becomes legible when distorted by shrinking.

    Shrink sleeve

    A plastic tube open at both ends or at least at one, usually made of PVC, which is shrunk around the neck / closure of a closed container by heat, in order to appear as visual control for tamper evidence.

    Shrink tunnel

    A device for subjecting packages wrapped in shrink film to the heat required to induce film shrinkage. Varies from table-top size to one large enough for a loaded pallet.

    Shrink Wrapping

    Packing method in which the residualstrains in a plastic film are released by raising its temperature, thus caus­ing it to shrink around the object or package being wrapped. The collating of 6 bottles into a single pack is often achieved with shrink wrapping with a shrinkage printed or non printed film.


    (1) A protective cover of waterproof bar­rier material used to shed water from top and sides of the article allowing free circulation of air. (2) A rigid housing surrounding a container in a vacuum-filling machine, to equalize vacuum pressure inside and outside the con­tainer and thus prevent its collapse during filling. (3) Shrink Shroud, a shrinkable coversheet able to secure a pallet load.

    Side seal

    A technique for producing plastic bags by folding a sheet of film and cutting and sealing the sides by heat or impulse sealing.

    Side seam

    1.A seam joining the two edges of a blank to form a container or can body. In a three-piece can, made by soldering, welding, glueing, or bonding. Main types of construction are lock seam, lap seam, Mennen seam.

    2.A seam formed on one side of a paper or plastic bag rather than at its centre.

    Sifter Fitment

    A plastic or metal component of a package designed to allow shaking out of dry products, as with a table salt shaker. Snaps over bead, with metal or plastic cap applied over the fitment.


    Pack construction preventing leakage or sifting of finely divided contents.

    Silica gel

    A form of colloidal silica resembling sand. Used as a desiccant to absorb moisture inside packages.

    Silk screen printing (serigraphy)

    Now called simply screen printing. Mostly used for printing irregularly shaped packages, such as glass or plastic bottles. Applies a thick coating of ink through a stencilled mesh screen.

    Single service

    A package containing a measured amount of product sufficient for use by one person, e.g. a condiment, a jam or jelly. In hospital use, an individually packaged dose of medicine.

    Single-trip container

    See: Non-returnable container.

    Sinkage/sink marks

    Defects in the form of surface depressions in moulded containers or components, often behind thread forms,that arise from diferent shrinkage of thick and thin sections as the article cools.

    Sisal fibre

    A fibre prepared from the leaves of agave, often used in the manufacture of cordage and twine. Can also be woven into bags, but the material is stiffer and more abrasive than jute fibre.

    Size (sizing)

    Resin, alum, starch or similar materials added to pulp or applied to the surface of paper and paperboard to add desired characteristics, such as water repellency, better printability, grease resistance, etc.

    Sized and Supercalendared (S&SC) paper

    A paper stock that has been sized with sizing insulatingand then highly calendared to produce a paper that has excellent surface requirements for printing.

    Size impression

    Apparent size of a product or package, possibly deceptive because increased by excessive pack height, wall thickness, internal voids, etc.


    A pair or a series of parallel wood runners attached to the underside of boxes or crates to permit movement and entry of truck forks.

    Skin packaging

    A packaging process in which a product is covered by a closely fitting usually transparent film. The product is placed on a porous rigid paperboard sheet; often printed, heated film is draped over it and vacuum is applied to draw the film tightly over the article. See also: Blister packaging.


    The vertical part of a closure below its shoulder.


    (1) A tubular form made of various mate­rials, usually open at both ends, made in various shapes, which is slipped over or in an item. (2) A tubular carton with open ends.

    Sleeve Label

    A decorated, plastic label in a tubular form that fits over and is shrunk on to rigid glass, metal and plastic containers.

    Slip (coefficient of friction)

    A measure of the tacki­ness or slipperiness of packaging materials. Slip is a key property for flexible packaging materials when it comes to their machineability.

    Slip Cap

    (1) A metal closure with indentations on its sides to make a friction fit on a vial with a slip-cap finish. (2) A closure made of soft material such as polyethylene or rubber, without threads, to be pushed over the tip or neck of a container and held in place by friction.

    Slip pad

    Pieces of wood used per pairs or more, positioned under the bottom of a case in order to facilitate its movement or at the end of the forks of a forklift.

    Slip sheet

    A corrugated or solid fibreboard sheet which fits under a unit load with an extension on one or more sides which can be grasped for pulling the load onto or off a pallet, etc.


    To cut a master roll or sheet of flexible material into smaller widths. This operation is done on a machine called a slitter. Usually carried out as a continuous high-speed operation in which one roll of material is converted into several narrower rolls.


    In a paperboard sheet, a cut of any length and with a normal width of about 3 mm, usually the space between the flaps of a box.


    (1) A solid strip of lead on which characters are cast in relief for letterpress printing, (2) A cylindrical piece of lead or aluminium alloy from which tubular containers can be impact extruded.

    Slush moulding

    The coating of a mould with a liquid plastic which when heated cures to form the ob­ject being molded.

    Snaplock bottom

    A particular style of a folding carton base consisting of four flaps, each cut away and hinged so that they interlock when the carton is erected.

    Snap Top closure

    The most prevalent hinged closure, it features an orifice that is sanitary and self cleaning to prevent clogging. It is available in a wide range of sizes. The closure can also be designed with an off-centre spout to direct product flow.

    Softening point

    Temperature at which plastic material will begin to deform with no externally applied load.


    Method for sealing the side seam and other joints of metal cans using a tin-lead alloy. Soldered seams are usually folded or hooked (lock seam), and must be lacquered to prevent corrosion and migration of metals into the product.

    Solid board

    Board made from multiple glued layers of flat paper and fibreboard material, without corrugations.

    Solids content

    The solids content of an adhesive is the weight of material expressed as a percentage of the total after all solvent has evaporated (by heat).


    A liquid into which a solid substance can be dissolved. In package converting, the component of an adhesive or coating solution which is evaporated from the web surface as the coated material dries.

    Solvent sealing

    A method of adhering packaging materials that depends on the use of volatile organic liquids in small amounts to soften the surface of the materials so that they adhere when the solvent evap­orates. The solvent has no adhesive prop­erties; adhesion depends solely on the adhesive properties of the melted materials themselves in solution.

    Specific gravity

    The ratio of the weight of a body to the weight of an equal volume of water at the same, specified temperature.


    A light measurement device used to determine colour values, such as chromatic value, (h*: hue) brightness (L*), and saturation (C*: chroma), with which colour can be clearly classified quantitatively in accordance with the colour perception of the human eye (in contrast to densitometers, which can only determine ink film thickness via the optical density).

    Spin welding

    A process of fusing
    two objects, typically packaging components, by forcing them together while one of the pair is spinning, until frictional heat melts the interface. Spinning is then stopped and pressure applied until the surfaces cool and seal together.

    Spiral winding

    A process for producing a cylindrical tube by winding several webs of paper and paperboard, foil, film, etc., around a stationary mandrel in a spiral pattern.


    1.(Noun) A joint accomplished by splicing.

    2.(Verb) To join the ends of reels or sheets of web materials such as foil, film, paper, etc. so that they can be handled continuously. The joint may be accomplished by mechanical or electrical means or using adhesives.


    Products and packaging spoiled in the process of manufac­ture; waste caused by mistakes; errors in judg­ment, or faulty processing; deterioration of food by microbiological action.

    Spot Colours

    Special colours used in addition to or instead of process colours (C, M, Y, K) to enable the printing of special hues without using the primary colours. Often also the only chromatic ink used in black-and-white printing.


    A fitting on a container to facilitate pouring of liquid or powder contents.

    Spray can

    See: Aerosol. See: Atomizer.


    (1) The primary feed channel that runs from the outer face of an injection or transfer mould to the mold gate in a single cavity mould or to the runners in a multiple cavity mould. (2) Plastic material left in the sprue section of the mould, usually separated from the moulded item, reground and reused.

    Squeeze bottle

    A bottle usually made from a flexible plastic such as polyethylene, from which liquid contents can be dispensed through a small aperture by squeezing the walls.


    A substance added to a plastic resin to enhance its resistance to chemical and physical change brought about by heat, pressure, light, etc.


    1.(Noun) A pile of containers or materials assembled in a regular vertical pattern.

    2.(Verb) To pile containers or materials on top of one another.

    Stacker Cap

    A closure designed to nest with a recess in the base of a container, to facilitate the stacking of filled containers on top of each other.

    Stacking strength

    The ability of a container to sustain a static top load. In corrugated boxes, the stacking strength is affected not only by the weight of the load, but also by elapsed time, and humidity.

    Stamping, hot-press or hot-die

    The process of stamping an image with metal leaf upon prepared paper, plastic or other packaging material using hot metal type or dies.

    Stand-up pouch

    Plastic or laminate pouch with a gusset spacing the side walls apart at the base so that it is able to stand.


    A U-shaped, round or
    flat, wire fastener used
    to secure package components together or in place. One of the three principal types of closures for setting up and sealing of corrugated boxes.

    Stapling machine or stapler

    A machine or device for applying staples.

    Static electricity

    Surface charges of electricity which may develop during handling and machine operations, particularly on plastics. Can lead to undesirable attraction of dust and may cause sparking and affect print quality. For this reason discharging devices are normally used. See also: Static eliminator.

    Static eliminator

    A device attached to a machine at one or more points to discharge the static electricity from the material being processed.

    Static load

    A steady, fixed force exerted upon a stationary object. See also: Stacking strength.


    (1) One of the shaped vertical units of wooden container which, when placed edge to edge and bound with hoops around a circular bottom (sometimes top and bottom), forms a barrel or other similar container. (2) One of the thin wood or veneer slats forming the body, sides, or cover of a basket or hamper.


    A piece of stiff material with marks or designs cut out in it through which inks or other liquids can be applied to a surface. Used in conjunction with marking inks for applying a product number or shipping information to packages.


    The ability of a material or package to withstand contact with steam at approximately 5 kg/m3 for 30 minutes or contact with dry air at 200 ºC for 15 minutes, and is therefore suitable for use with sterilized products.


    Resistance to bending. The degree of stiffness may be measured by several instruments, the most common being a Taber stiffness tester.


    (1) A decoration consisting of a system of small, cIosely-spaced raised dots on the outer surface of glass containers. (2) In engraving, a printing surface consisting of dots, instead of lines; halftone patterns on a printing plate are stipple engravings.


    1.(Noun) The thread or wire joining materials by means of the stitching process.

    2.(Verb) To unite materials or surfaces by means of an interconnecting thread or wire.

    Stochastic halftone

    Halftone printing achieved by means of randomly spaced, varied-density dots of fixed size.


    A closure, usually cylindrical, made of glass, wood or cork or plastics, which can be removed and reinserted into the aperture of a container.

    Strap (strapping)

    A flexible strip of material used for closing or reinforcing transport packages or for securing unit loads. Either non-metallic (nylon, polypropylene, polyester) or metallic straps can be used; both types are usually joined with metal clips but heat welding can also be used.

    Strapping tools

    Hand-held equipment for tensioning and sealing various kinds of straps.


    Board made from straw pulp. Used in many parts of the world where wood pulp is not readily available, though its performance is generally inferior from most standpoints.

    Stress crack

    External or internal cracks in a plastic material caused by stress but often accelerated by environmental influences and by the nature of products in contact with the plastic.

    Stretch film

    A thermoplastic film, generally polyethylene or PVC which is extensible under load and tries to return to its original dimensions when the load is removed thus providing a tensioned wrap around a package or object.

    Stretch forming

    A plastic sheet-forming tech­nique; the heated thermoplastic sheet is stretched over a mould and subsequently cooled to produce a tray or dish.

    Stretch wrapping

    The use of stretch film to produce a tightly wrapped package which conforms to the shapes being wrapped. A common method for securing unit loads on pallets without the use of heat.


    In plastic bottle manufacturing, a longitudinal line in the parison or bottle due to a disturbance in the melt path. Such a visual defect may also lead to mechanical weakness.

    Strike-through (of adhesive or printing)

    Discoloration or de­fect of appearance of the reverse of a glued or printed sheet caused by migration of solvents or pig­ments, or by excessive porosity of the sheet.

    String and button

    A method of closing a paper bag or envelope pack with a string and attaching it to a fibre but­ton fastened to the pack. Usedfor hotel laundry bags, for example.


    A wooden member to which the face or faces of a pallet are fastened and placed at right angles to the members making up the pallet face.


    The property of an adhesive to draw filaments or threads when adhesive-transfer surfaces are separated, causing webs of unwanted adhesive to form outside the glued area.

    Strip packaging

    A method of packaging in which small articles, such as capsules or tablets, are packaged individually or in multiples, in a continuous strip made from two webs of material using foam-fill-seal techniques. The strip pack is usually perforated to permit easy tearing or cutting. At least one of the materials is generally transparent and the webs carry a heat sealable coating.(Pharmaceutical packages).

    Styrene plastics

    Plastics made by the polymerization of styrene or copolymerisation of styrene with other unsaturated compounds.  Converted to film, sheet, foam and molded trays, cups, bottles and closures.


    The base web, of paper, film or foil, onto which a secondary material is applied. The term is frequently used when discussing printing, coating or laminating onto packaging materials.

    Sulphate paper

    Chemical wood pulp made by the sulphate process, or paper or paperboard made from such pulp. It is brown in color and is the strongest pulp product made from wood.


    Stack of alternate metal and soft rubber rolls between which a paper undergoing processing is passed. Used to increase smoothness and gloss of paper and to control caliper.

    Sure lock flap

    A tuck-in carton flap having slits which engage a shaped edge of the inside dust flap, thus effectively locking the carton.

    Surface treatment

    See: Corona treatment.

    Sustainable packaging

    Packaging that can be used, or recovered and recyled indefinitely and is not dependent on the availability of finite and non-reproducible resources.


    Expanded hoops pressed out in metal drum bodies for strengthening and to facilitate rolling.

    Swell, hydrogen

    A bulged end of a closed metal can, arising from pressure of hydrogen gas generated by reac­tion of metal with the contents.


    Anything produced by other than natural means to resemble a natural product or to reproduce its properties e.g. synthetic fibres such as nylon, polyester, etc.

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