Converting Glossary

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ANCHORED COATING: a coating applied to a base sheet (usually bonded) so it very strongly resists separation

ANNEALING: technique of keeping a material for a period of time at a temperature short of melting, to relieve internal stresses; the application of heat to a formed or oriented plastic article to relieve stress resulting from the forming or orientation process

ANTI-BLOCK: the name for a treatment applied to plastic film surfaces to keep them from sticking together or “blocking” when they are tightly rolled up on a mandrel

ANTI-OXIDANT: a substance that prevents or reduces oxidation of the material by air or oxygen

ASEPTIC: free from septic matter or disease-producing bacteria. In food processing or packaging, this is an adjective that describes the system used to package food in a sterile fashion.


BAG, CRIMP-BOTTOM: a flat bag with a crimp-seal bottom (no fold-over) usually heat-sealed using serrated dies. Not a particularly strong type of bag. (See: Flat Bag)

BAG, DUPLEX: a bag constructed of two piles of material, generally spot-sealed to each other, especially at the mouth
BAG, FLAT: simplest form. A web of material folded into a flat tube with side or center seam, then cut off and sealed at one end. Has only two dimensions: length and flat width. Flat bags may have a crimped seal or a fold-over seal, in which a short section is turned back and sealed in place by heat, adhesives, or a combination of both.

BAG, GUSSETED: bag having bellows-like folds on each side that expand outward when the bag is filled

BAND: in cellophane, a dark-colored circumferential ring in a slit roll, caused by a slightly heavier moisture content, or very slight variations in base-sheet thickness

BANDS, BAGGY: a defect in a roll of film; a slack lane or a baggy section which shows up when film is unwound and pulled taut

BEAD: a thickened section at the edge of a roll of film. In cellophane slit rolls usually caused by moisture absorption into the cellulose base sheet.

BETA-RAY GAUGE: consists of two facing elements, one emitting and one detecting beta radiation. The device accurately measures density or thickness when mounted above and below the web.

BIAXIAL ORIENTATION: a process for orienting a plastic film in both the transverse and the machine directions

BLEEDING: diffusion, especially of inks, into areas adjacent to those that were intended to be printed

BLISTER PACK: package formed from semi-rigid thermoplastic material so that the sheet forms a transparent dome over the packaged item

BLOCK, BLOCKING: undesired adhesion of two or more piles of material in roll or sheet form. May be caused in cellophane by exposure to excessive heat, pressure, or humidity; in printed film, occasionally caused by improper or insufficient drying of inks, resulting in printed areas sticking together.

BLUSH, BLUSHING: hazy or foggy appearance occasionally noted in coated films

BON: Biaxially Oriented Nylon

BREATHING: passage of gases in and out of a package. Certain films are designed to permit it.


CELLOPHANE: transparent film made from regenerated cellulose, a fibrous material occurring in plants.

CELLULOSE, REGENERATED: cellulose that has been chemically treated, then regenerated as a transparent film

CEMENT: in the adhesive sense, a substance bonding two materials by chemical or solvent action.

CHEEK-PLATES: discs used at each end of paper or rolls of film to prevent “telescoping” of material

CLARITY: freedom from haze; transparency

CLING: adhesion of packaging film to machine surfaces; “drag.” Often caused by tackiness or static electricity charges in plastic films.

COATING, FILM: a coating applied to provide protective, decorative, pressure-sensitive, waterproof, or heat-sealable qualities to the base sheet

COATING, HEAT-SEAL: a coating, applied to a base sheet, which may be activated by heat to permit the fusion or seal of one section of the film to another

COEXTRUSION: simultaneous extrusion of more than one polymer layer into a film

COF: Coefficient of Friction

COHESION: the tendency of a mass to hold together by primary or secondary valence forces (intermolecular attraction)

COLOR-OFF: in cellophane, slit roll edge may display variation in color or shade; off-color film is not usually defective and will almost always perform on machines

CONTOUR PACKAGE: package formed of semi-rigid material, usually by shaping a heated sheet by pressure or vacuum so that it follows the contours of the packaged item very closely

CONVERTER, PACKAGING: equipment which processes raw packaging stock such as cellophane, foil, etc. into a more advanced state, generally by forming, printing, gluing, laminating, etc.

CORONA TREATMENT: subjecting a polymer film to an electrical discharge to alter its surface characteristics.

CRATERING: thin or bare spots in a film that appear as pockmarks

CRAZING: network of fine lines in or on a coating or transparent surface: “spiderweb” or “dried mud” pattern

CRIMP SEAL: seal produced in cellophane or other material by means of elements having corrugated surfaces; lends mechanical rigidity to seal areas as well as ensuring maximum area contact of film surfaces.

CROCKING: smudging or rubbing off of ink after printing

CURL: in packaging films, distortion frequently caused by the absorption, or loss, of moisture at an uneven rate from one side of a sheet; curl may also be caused by uneven physical stresses, as in the case of laminations or coated materials

CUT-OFF LENGTH: length of sheet fed by automatic wrapping machine during operation

CYCLE TEST: test program in which items are exposed alternately to two or more test conditions


DEAD-FOLD: fold in packaging material which will remain in place without sealing, as in the case of folds made in soft lead foil or aluminum foil

DIMENSIONAL STABILITY: the absence of dimensional change of a material when subjected to changes in temperature, humidity, heat, or aging

DOCTOR-BLADE: scrapers that regulate the thickness of adhesives, or inks, on a feed roller

DOWNGAUGE: use a thinner film than had been previously used

DRAW-DOWN: thinning in gauge or narrowing in width, especially of extruded materials, as a result of windup rate exceeding speed of extrusion, stretching


ELECTRONIC SEALING: sealing of surfaces in contact with one another by high frequency current, e.g., sealing vinyl sheet. Heat is generated within the film by high-frequency agitation of the sheet’s molecular structure.

EMULSION:  a non-separating dispersion or suspension of a solid in a liquid

EXTRUSION LAMINATION: a process for joining two webs by feeding them through a machine that extrudes a thin layer of plastic between them to act as an adhesive


FILM, CALENDERED: a film manufactured by forcing base material through rolls of a calendering machine, making it smooth and glossy

FILM, CAST: (1) film made by pouring or metering material onto a highly polished moving drum or endless belt, or (2) film produced by extruding into a solution, as in the case of cellophane

FILM, EXTRUDED: film produced by the extrusion method

FILM, NON-FOGGING: film that does not become cloudy from condensation of moisture caused by temperature drops or humidity changes

FILM, ORIENTED: film in which the molecular structure is aligned mechanically in one or more directions, thus giving the film more strength while introducing shrinkage characteristics

FIN SEAL: seal that results when edges of two superimposed sheets are bonded, resulting in a pouch having fin-like protuberances

FISH-EYES: particles of undissolved extraneous material in a film or coating

FLAT SEAL: a method of heat-sealing thermoplastic films with a flat bar surface

FLEX CRACK: cracking in a film produced by repeated flexing

FLEX STRENGTH: the ability of a sheet or film to withstand breakage by folding. Measured by a test to determine the number of folds required to cause failure.

FRACTIONAL PACKAGING: interior packaging of individually wrapped units so that unused portions will be protected after outside package has been opened. Usually used for biscuits, crackers, and ready-to-eat cereals.

FUSE: weld of thermoplastic materials by heating to point just above that at which they soften


GAS PACKAGING: packaging in a gas-tight container in which air has been replaced by a gas such as carbon dioxide or nitrogen

GAS TRANSMISSION: the movement of gas, air, oxygen, etc., through a film material. The gas transmission property (permeability) of a film is measured in terms of the volume of gas (at standard temperature and pressure) transmitted through a given area of film of a given thickness, within a given time.

GASSING: (1) development of gas in a sealed package. (2) removing air from a filled package and replacing it with another gas such as carbon dioxide or nitrogen

GAUGE: thickness expressed in decimals of an inch or in millimeters

GEL: a general term used to describe a defect consisting of insoluble polymer causing a visible discontinuity in a film

GHOSTING: reproduction, very faint, of printed design without actual ink transfer

GLASSINE: smooth, dense-structured super-calendered paper, translucent or opaque, made from heavily beaten fibrillated chemical wood pulp. Grease-resistant, tough, pliable.

GLASSINE, COATED: the coating types available include hot melt-applied paraffin waxes and derivatives, as well as solvent-applied types made from cellulose nitrate, vinyl polymers, and other synthetic or natural rubber polymers

GLASSINE, LAMINATED: glassine laminated to itself, or other paper, films, and foils, to obtain added strength and made-to-order protective water-vapor properties


HDPE: abbreviation for High Density Polyethylene

HEAT SEALING: a method of bonding two or more surfaces by fusing thermoplastic or thermosetting coatings of films under controlled conditions of temperature, pressure, and time (dwell)

HERMETIC SEAL: a seal that will exclude air and be leak-proof

HOT-STAMPING MACHINE: marking machine that applies a code mark or date on a package or wrapper with a heated stamp

HOT TACK: the property of an adhesive or seal layer to resist forces that would pull the seal apart while it is still hot

HUMIDITY: water vapor in air. Absolute humidity is the weight of water vapor contained in a unit of air. Relative humidity = percentage of actual humidity to the maximum humidity which air can retain without precipitation at a given temperature and pressure.

HYGROMETER: an instrument for measuring the moisture of relative humidity in the atmosphere

HYGROSCOPIC: having the property of absorbing moisture readily from the atmosphere


ID: Inside Diameter

IMPACT STRENGTH: resistance of a material or product to shock, such as from dropping and hard blows

IMPREGNATION: saturation of a material with another substance

INK, GRAVURE: pigment dissolved or dispersed in a vehicle made from resins and solvents; very fast-drying

INK, IMPRINTING: ink specially designed to be used with a marking device

INK, MOISTURE-SET: ink formulated to be stable under normal humidity conditions, but to set up or harden when exposed to very high humidity

INK, THERMOSETTING: ink formulated to be stable and free from tack at ordinary temperatures but to set up quickly at elevated temperatures

IRREGULAR WINDING (Projecting film): peaks or ridges in a slit roll that extend out more than 1/32” from edge of main body of roll

IRREGULAR WINDING (Lateral weave): a defect whereby a difficulty shows up as failure of film to feed in straight line during use


LABEL, HEAT SEAL: a label coated on one side with a heat seal coating, usually a thermoplastic resin

LAMINATE (noun): a structure made by bonding together two or more layers of material or materials. (verb) action of combining finished films to produce the laminate

LAMINATED FILM: combination of two or more films or sheets made to improve overall characteristics

LAP SEAL: any seal made between two overlapping films. Used in contrast to a “fin seal.”

LDPE: abbreviation for Low Density Polyethylene

LIP: that part of the tube of a flat or square bag, or pouch, extending beyond the face of the bag

LITHOGRAPHY, OFFSET: printing process using etched metal plates. Ink adheres to etched area, is transferred to rubber printing blanket, and from there to paper to be printed

LLDPE: abbreviation for Linear Low Density Polyethylene


MAKE-READY: in printing, preparation of press for a run; especially, making all printing surfaces uniform in height

MASTER ROLL: the large roll of film wound during a film formation process, which is normally slit into smaller rolls for later processing or shipment

MD: abbreviation for Machine Direction

METALLIZING: the process of applying an extremely thin metal coating to a non-metallic surface

MIL: one thousandth of an inch

MODULUS: in packaging, used to denote the degree to which a film or sheet resists stretching before it reaches its elastic limit when an external force or stress is applied

MSI: abbreviation for a thousand square inches, a common unit for pricing laminated films

MVTR: abbreviation for Moisture Vapor Transmission Rate


NITROCELLULOSE: any ester of nitric acid and cellulose

NICKED EDGES: edges of split film or form

NON-FLAMMABLE OR NON-INFLAMMABLE: will not support combustion


OD: Outside Diameter

OFFSET: accidental transfer of printing inks or coating from surface of a sheet to back of another sheet

OPACITY: resistance of material to transmission of light

OPP: Oriented Polypropylene

OPTICAL DENSITY: a measure of opacity of a metallized film layer. It is the log of the ratio of the intensity of transmitted light to incident light.

OPTICAL DISTORTION: change in appearance of object when viewed through a transparent material having certain defects, such as waviness of surface, etc.

OVERPRINT: the result of printing one layer over another, such as one layer of ink printed over another one to form color combinations

OXIDATION: reaction of any substance with oxygen


PACKAGING, FLEXIBLE: packaging involving the use of such flexible material as foils, films, paper, etc. to form the container

PACKAGING, FRACTIONAL: the breaking down of a unit package into two or more sub-units, which the objective of protection of the sub-units

PAPER, SULFATE: kraft paper, a chemical wood pulp paper (the strongest pulp paper made from wood)

PAPER, SULFITE: any type of paper made from pulp produced by the sulfite chemical process. Used in packaging applications where appearance and printability are of primary importance.

PAPER, WAX OR WAXED: all papers that have been impregnated, coated, or otherwise treated with waxes or waxlike materials

PAPERBOARD: a heavyweight thick sheet of paper, usually a thickness of 0.06” or over

PARCHMENT, ARTIFICIAL: certain greaseproof papers made by wholly physical means, but having no natural wet strength; resembles vegetable parchment

PARCHMENT, VEGETABLE: a vegetable-base paper having no taste or odor, consisting only of pure cellulose. Highly greaseproof, and outstanding in wet strength.

PE: abbreviation for polyethylene. Used when someone wants to avoid being specific, but is usually synonymous with low-density polyethylene.

PEEL-SEAL: a package seal made using an adhesive that can readily be peeled open

PEELING BOND: a type of bond that occurs when two adhered surfaces may be pulled apart without tearing the fibers

PERMEABILITY: ability to be permeated by gases or liquids; a measure of the freedom with which gases or liquids can diffuse through a material

PET: polyester film

pH: numerical representation of acidity or alkalinity. Neutral is pH 7; pH 1 is extremely acidic, and pH 14 is extremely alkaline.

P1 TEST PROCEDURES: a large body of standard test methods developed or recommended by Technical Committees of Packaging Institute to provide uniform and reliable tests

PICK-UP ROLL: a spreading device where the revolving roll for picking up the adhesive runs in a reservoir of liquid adhesive

PLASTICIZER: an agent or compound that is added to plastic materials to impact softness or flexibility

PLASTICIZER MIGRATION: movement of plasticizer to the surface of a plastic, or from one plastic to another, or from a plasticized substance into the atmosphere; causes embrittlement

PLATE (noun): curved or cylindrical shape carrying printing impression; for use on a printing press

POLYMER: a compound formed by the linking of simple and identical molecules having functional groups that permit their combination to proceed to higher molecular weights under suitable conditions

POLYPROPYLENE: a synthetic thermoplastic material of high molecular weight resulting from polymerization of propylene gas under pressure and heat, plus catalysts

POLYSTYRENE: a thermoplastic material derived from the polymerization of styrene monomers

POROSITY: of sufficiently loose texture to permit passage of gases or liquids through pores

POUCH. PLICATED: a folded pouch having gussets

PPR: polypropylene

PRESS POLISH: a finish for plastic sheet stock, produced by contact under heat and pressure with a very smooth metal, which gives the plastic a very high sheen

PRIMER, PRIMED: the act of putting a thin coating on a substrate so that it will be more receptive to printing inks or adhesives

PRINTING COMPENSATOR: a mark printed at regular intervals on the film which actuates a photoelectric cell on the bag machine or wrapping machine to ensure the perfect register of copy on a bag or package

PRINTING, FLEXOGRAPHIC: formerly called aniline printing. A method of rotary letterpress printing that employs flexible rubber plates and rapid-drying inks

PRINTING, GRAVURE: a rotary printing process employing minute engraved “wells” in an etched metal cylinder. Deeply etched wells carry more ink than shallower ones, hence print darker values. A doctor blade wipes excess ink from the printing cylinder. Stok is web-fed from roll.

PSYCHROMETER: a hygrometer for measuring water vapor in the atmosphere

PULLOUT, GOOD: no puckers or banded lanes showing when film is stretched


REGENERATED CELLULOSE: a cellulose hydrate. The term is used to designate films made from a cellulose base.

REVERSE PRINTED: the process in which a transparent film is printed backwards so that when it is flipped over, the printing appears right side up. When used in a package, reverse printed film will always have the printing ink on the inside where it is protected from scuffing and abrasion.

REWIND: to wind again; especially the winding of a roll of film after printing, slitting, etc.

RH: relative humidity

ROLL FORMATION: a general term denoting qualitatively how evenly, smoothly, and regularly film is wound on a roll


SERRATED: saw-toothed. Describes the configuration used on heat-sealing equipment for obtaining a crimp seal.

SLIP: a measure of COF (coefficient of friction). High slip means low COF.

SLIT: to cut a roll of stock to narrower widths

SLITTER: a machine to cut a roll of stock in the long direction

SOLVENT SEALING: a method of adhering packaging materials which uses small amounts of volatile liquids to soften the coating of the material so it will bond. Examples: cellosolve ethyl lactate, etc.

SPECIFIC GRAVITY: the ratio of the weight of a body to the weight of an equal volume of water at some specified temperature

SPLICE: to unite or join the ends of roll materials by mechanical or electrical means, or by an adhesive

STATIC ELECTRICITY: charges of electricity sometimes generated during handling or in machine operations; may cause undesired attraction of film to roller, flat surfaces, etc.

STERILE SEAL: a closure for bacteria-free medical supplies that must maintain sterility

STERILIZABLE: the ability to withstand contact with steam (moist heat) at 30 lb. pressure for 30 minutes, or contact with dry heat (circulating hot air) at 200 degrees C for 15 minutes

STRIP-PACKAGING: small articles packaged individually or in multiples in continuous strips, divided in segments or pockets that permit easy tearing or cutting off

SUBSTRATE: a film to which subsequent coatings or layers are added

SURFACE PRINTING: printing on the outside surface of a package as opposed to one of the inside surfaces (see “REVERSE PRINTING”)

SURFACE WINDING: a method of winding film on rolls in which the winding force is provided by the driven roll in contact with the surface of the winding roll

SURLYN: Dupont’s trademark for its line of ionomer resins. Films produced with this resin have excellent seal characteristics such as lower sealing temperatures and excellent hot tack.


TAPE, CELLULOSE ACETATE: a translucent, pressure-sensitive adhesive tape of cellulose acetate laminated to strong tissue

TD: abbreviation for transverse direction – the direction perpendicular to the machine direction

TEAR STRENGTH: the force required to propagate a tear already initiated by a cut on the edge

TEAR STRIP: a narrow ribbon of film, usually incorporated in the wrapper or overwrap during the wrapping operation, to facilitate opening of the package

TELESCOPING: side-slipping of layers of a coiled material so that the edges no longer form a plane surface

TENSILE STRENGTH: resistance of a material to longitudinal tension

TEST, CELLOPHANE TAPE: a simple test for determining the permanency of printing on plastic film. A length of pressure-sensitive cellophane tape is pressed on a section of printing and then pulled off in one motion to see whether or not the ink lifts with it. The angle and speed of the pulls are important.

TEST, DROP: a package durability test. Filled containers are dropped from controlled heights. A special device ensures uniformity of drops.

TEST, DRUM: rough-handling test for filled container, inside a revolving hexagonal drum

TEST, ELMENDORF TEAR: a method of testing the film for resistance to tearing. The weight required to tear one of several layers of notched film is measured.

TEST, FOLDING ENDURANCE: a test to evaluate the endurance of films to folding, frequently done on a Schopper machine

TEST, MULLEN: The Mullen Is widely used on film packaging materials to determine the relative bursting strength.

THERMOCOUPLE: a bimetallic device to measure temperature electrically

THERMOPLASTIC: capable of being repeatedly softened by heat and hardened by cooling

THERMOSTAT: an automatic device for regulating temperature; uses bimetallic strip to make and break contacts of electrical circuit

THERMOSET: plastic that is heat-set

THERMOWELD: to weld together two or more surfaces of a thermoplastic film material by means of heat

TIE LAYER: the common term for a coextrudable adhesive

TRACKING: a film that follows a desired path on a packaging machine without constant adjustment is said to “track” well

TRANSLUCENT: permitting passage of light, but diffusing it to such a degree that objects cannot be seen clearly; something short of transparent

TRANSPARENT: transmitting rays of light so that objects can be clearly seen through the material


UNDERFOLD: to fold wrapping material in such a manner that the end folds are turned under the bottom of the package, then sealed to the underside


VAPOR TRANSMISSION: the passage of vapor (usually water vapor) through a material

VFFS: abbreviation for Vertical Form-Fill-Seal

VISCOSE: a viscous orange-colored liquid obtained by treating cellulose with caustic alkaline solution, then with carbon disulfide

VISCOSITY: that property of a liquid material that tends to resist flow

VOLATILE: passing from a liquid into a gaseous state

VOLATILITY: the rate of evaporation of a solvent


WATER VAPOR PERMEABILITY: the ability of a material to permit transmission of water vapor

WATER VAPOR TRANSMISSION RATE: measure of permeability of a material, often stated in terms of grams of water passing through 100 square inches of material in 24 hours at 100 degrees F and 90 percent relative humidity

WAX, MICROCRYSTALLINE: a petroleum wax of high molecular weight, characterized by minute crystals and distinguished by its solid wax-like appearance at room temperature

WEB: a term to denote a long film somewhere in the processing stage, frequently being drawn off a large roll. For example, a “printed web” would be a large roll of printed film.

WORMING: channel-like delamination pattern in adhesive-laminated materials

WRAP, BUNCH: wrapping with packaging material gathered on the underside of package in somewhat irregular manner

WVTR: abbreviation for Water Vapor Transmission Rate


YIELD: area per unit of weight, usually expressed as square