Packaging Testing, Quality and Defects Glossary

How to use this glossary

The page is written for buyers, quality managers and packaging engineers who need to read a test report or write a quality requirement without a laboratory background. Entries are grouped into thematic sections and listed alphabetically within each. Headings give the term, its abbreviation and standard numbers and, where useful, the German (DE) term found in specifications from Germany and Austria. Typical values are labelled as such, because results depend on material, method and laboratory; the values that apply to an order are agreed in its specification. Standard numbers are cited only where the method is well established, and a test report should always name the exact method and edition used.

This page is part of the packaging glossary. Related sub-glossaries cover printing and prepress terms, converting and manufacturing terms, packaging materials and regulation, sustainability and trade. How samples, approvals and inspections fit together in practice is covered in packaging sampling and quality control.

Packaging testing standards at a glance

The table lists the most frequently quoted packaging test methods with their usual standards and reporting units. Several methods exist in more than one standard; values from different methods are not always interchangeable.

Test conditions and measurement basics

Paper, board and corrugated change properties with moisture, and every test has its own scatter. These terms explain why two reports on the same material can disagree.

Conditioning (standard atmosphere; ISO 187; TAPPI T402; DE Normklima)

Conditioning is holding paper, board or corrugated samples in a controlled climate until their moisture content is stable before testing. The standard atmosphere under ISO 187 and TAPPI T402 is 23 °C and 50 % relative humidity, with 27 °C and 65 % RH as an alternative for tropical countries, and samples are usually preconditioned in drier air so they reach equilibrium from the dry side. Almost every strength value of fibre-based packaging depends on moisture, so results from unconditioned samples are not comparable.

Moisture content (ISO 287)

Moisture content is the mass of water in paper or board as a percentage of its mass as sampled, determined by oven drying to ISO 287. Packaging papers and boards typically leave the mill at roughly 5-9 % moisture, depending on grade, and values outside the agreed range cause curl, warp, cracking at folds and weak glue bonds. Board shipped through humid climates takes up moisture in transit, which is why moisture is checked on incoming material.

Repeatability and reproducibility

Repeatability is the variation between results when one operator tests the same material on the same instrument within a short time; reproducibility is the variation between different laboratories testing the same material. Standards publish both, and reproducibility is usually much larger, which is why a supplier's value and a buyer's laboratory value can differ without either being wrong. Disputed results are best settled by retesting retained samples in one agreed laboratory.

Specification limit and tolerance

A specification limit is the minimum, maximum or target value agreed for a property, and the tolerance is the permitted deviation around a target, for example grammage 80 g/m² ± 4 % or ECT minimum 5.0 kN/m. One-sided limits suit strength properties, while two-sided tolerances suit weight, thickness and dimensions. A limit that is not written into the specification cannot be enforced at inspection.

Typical value and guaranteed minimum

A typical value on a data sheet is the average a mill or converter expects to achieve, while a guaranteed or minimum value is the level every lot should meet. For strength properties, typical values are often well above minimums, so comparing one supplier's typical figure with another's minimum is misleading. Specifications should state which kind of value applies and which method it refers to.

Paper and board tests

Laboratory tests for the paper and board itself, before conversion. Grade selection is covered in packaging paper grades explained and materials in the packaging materials glossary.

Air permeance (porosity; Gurley, Bendtsen; ISO 5636)

Air permeance, often called porosity, is the rate at which air passes through a sheet under a set pressure difference. The Gurley method (ISO 5636-5) reports the seconds needed for 100 ml of air to pass, so higher numbers mean a more closed sheet, while the Bendtsen method (ISO 5636-3) reports flow in ml/min, so lower numbers mean a more closed sheet. Greaseproof and glassine papers have very low permeance, and permeance affects how coatings, adhesives and vacuum feeding on converting machines behave.

Bending stiffness (Taber, L&W; ISO 2493; DE Biegesteifigkeit)

Bending stiffness is the resistance of paper or board to bending, measured either as bending resistance in millinewtons on an L&W-type tester (ISO 2493-1) or in Taber stiffness units on a Taber-type tester (ISO 2493-2). Stiffness rises roughly with the cube of thickness, so bulky boards are stiffer per gram, and it is quoted separately in machine and cross direction. It governs how a carton resists bulging, how a cup wall feels when gripped and how blanks run through folding and forming machines.

See: FBB vs SBS vs WLC

Brightness and whiteness (ISO 2470; CIE whiteness)

ISO brightness is the reflectance of blue light at a wavelength of 457 nm from a pad of sheets, measured to ISO 2470-1 and used to grade bleached papers and boards, while CIE whiteness weights the whole visible spectrum and reacts more strongly to optical brighteners. Neither value describes shade, which is measured in CIELAB L*, a* and b*. Brightness and shade differ between virgin and recycled grades and between mills, which shows when packs from two suppliers sit side by side.

Burst strength (Mullen test; ISO 2758, ISO 2759; DE Berstfestigkeit)

Burst strength is the pressure needed to rupture paper or board pushed from one side through a circular opening by an expanding rubber diaphragm, reported in kPa under ISO 2758 for paper and ISO 2759 for board, or in psi under TAPPI T 810 for corrugated board. Burst index, burst divided by grammage, compares papers of different weights. Burst reflects liner tensile strength and stretch and correlates with puncture resistance, but says little about stacking performance.

See: corrugated board grades for mailer boxes

Caliper (thickness; ISO 534; DE Dicke)

Caliper is the thickness of a single sheet of paper or board, measured with a micrometer under defined pressure on a defined area to ISO 534 and stated in micrometres, or in US points where 1 pt equals 25.4 µm. Bulk (cm³/g) and density (kg/m³) are calculated from caliper and grammage. Caliper drives stiffness, crease and die settings and the stack height of flat blanks, so variation shows up in folding, forming and filling.

Grammage (gsm; ISO 536; DE Flächengewicht, Grammatur)

Grammage is the mass of one square metre of paper or board in g/m², determined by weighing sheets of known area to ISO 536. Mills and converters work to tolerances around the nominal value, typically a few per cent, and grammage is the basis of material cost and EPR weight reporting. It says nothing about thickness or strength on its own, so it is checked together with caliper and the relevant strength test.

See: paper bag GSM guide

Internal bond strength (ply bond; Scott bond; z-directional tensile)

Internal bond strength is the resistance of paper or board to splitting within its thickness, measured by pulling the sheet apart perpendicular to its surface (z-directional tensile, ISO 15754) or by an impact-type Scott bond test reported in J/m². Low internal bond in multi-ply board shows as delamination at creases, under glued flaps or when labels and tape are removed. It matters for cartons that are glued, heavily creased or printed with high-tack inks.

Smoothness and roughness (Bendtsen, PPS, Bekk, Sheffield)

Smoothness tests measure how flat the surface of paper or board is, which governs print quality, especially fine text and halftones. Air-leak methods are most common: Bendtsen roughness (ISO 8791-2) and Sheffield report air flow, so lower values are smoother, Parker Print-Surf (PPS, ISO 8791-4) reports roughness in micrometres, and Bekk smoothness (ISO 5627) reports seconds, so higher values are smoother. Results from different methods cannot be converted into each other reliably.

Stretch (elongation at break; paper)

Stretch is how far paper extends, as a percentage of its original length, before it breaks in a tensile test to the ISO 1924 series. Ordinary kraft papers typically stretch a few per cent in machine direction, while extensible sack kraft is made to stretch considerably more, which raises the energy the paper absorbs before failure. High stretch helps bags and sacks survive drops, snags and sudden loads on handles.

Tear resistance (Elmendorf; ISO 1974; DE Weiterreißwiderstand)

Tear resistance is the force needed to continue a tear already started in paper, measured with a falling-pendulum Elmendorf tester to ISO 1974 and reported in mN, with tear index dividing the value by grammage. It is quoted for both machine and cross direction and is usually higher in cross direction. It shows whether a nick at a handle cut-out, gusset fold or tear notch is likely to run into a rip.

Tensile strength and TEA (ISO 1924; DE Zugfestigkeit)

Tensile strength is the maximum force per unit width a paper strip withstands before breaking, reported in kN/m under the ISO 1924 series, while tensile energy absorption (TEA, J/m²) is the energy the strip absorbs up to failure. Tensile strength is higher in machine direction than in cross direction, and both values are tested at the ISO 187 climate of 23 °C and 50 % relative humidity. They govern handle and patch strength on carrier bags, seam strength and the drop performance of sacks.

See: paper bag handle types

Wet tensile strength (wet strength; ISO 3781)

Wet tensile strength is the tensile strength of paper after soaking in water for a set time (ISO 3781), often expressed as a percentage of dry tensile strength. Ordinary papers keep only a small fraction of their strength when wet, while wet-strength papers made with wet-strength resins typically keep more than about 15 %. It matters for napkins, food bags exposed to condensation and wraps for moist or iced products, although wet-strength paper is harder to repulp.

Grease, water and coating tests

Tests for how paper and board resist oil, water and liquid at cut edges, and whether barrier coatings are continuous. Barrier technologies are compared in barrier coatings for paper packaging.

Cobb test (Cobb60; ISO 535; TAPPI T441)

The Cobb test measures how much water a paper or board surface absorbs in a set time when covered with water over a fixed area, reported in g/m² under ISO 535 or TAPPI T441. Cobb60 means a 60-second exposure, and longer exposures such as Cobb1800 (30 minutes) are used for heavily sized or coated grades. Lower values mean better water resistance, which matters for liners, cupstock, food bags and boxes for wet or saucy food.

See: takeaway boxes for wet food

Edge wicking (edge wick test)

Edge wicking is the penetration of liquid into the exposed raw edge of board, such as a cup side seam or the cut edge of a container, where no coating protects the fibres. It is tested by immersing an edge-exposed sample in a liquid chosen for the end use, such as hot water, coffee, lactic acid or hydrogen peroxide, and measuring the uptake per unit of edge length. Cupstock is internally sized to keep edge wicking low; high wicking shows as staining and softening along seams.

See: paper cup linings

Grease permeation test (ISO 16532-1)

The grease permeation test of ISO 16532-1 measures how long oil takes to pass through paper by applying a test oil, palm kernel oil in the standard method, to flat and creased samples and checking an absorbent sheet beneath for staining over time. Unlike the KIT test, it measures penetration through the sheet over hours and includes folds, which is closer to how a wrap or bag behaves with real food. Results are stated as time to failure or as the proportion of stained area.

See: KIT test and grease resistance ratings

KIT test (TAPPI T559; ISO 16532-2)

The KIT test rates the surface oil repellency of paper with twelve numbered mixtures of castor oil, toluene and heptane of increasing aggressiveness; a drop of each is left for about 15 seconds, wiped off and the spot checked for darkening. The KIT rating from 1 to 12 is the highest-numbered solution that does not stain the paper. Published as TAPPI T559 and ISO 16532-2, it is a fast screening test that does not measure performance with hot food over minutes or at folds.

See: KIT test and grease resistance ratings

Pinhole test (coating continuity)

A pinhole test checks whether a barrier coating or film layer is continuous by applying a dyed or penetrating liquid, such as coloured turpentine or an ink solution, to the coated side and looking for spots on the reverse or on a blotting sheet. Pinholes come from coating weights that are too low, rough board, dust or damage at creases. They matter for grease-barrier papers, cupstock and lidding because a single pinhole can cause a stain or a leak.

Turpentine test (TAPPI T454; ISO 16532-3)

The turpentine test measures how long dyed turpentine takes to penetrate greaseproof or glassine paper through voids in the sheet, as described in TAPPI T454 and ISO 16532-3. Long penetration times indicate a dense, closed sheet with few pinholes. It is an older method that still appears in specifications for greaseproof and glassine papers alongside the KIT test.

Corrugated board and box tests

Tests on containerboard papers, combined board and finished boxes. How these values translate into board grades is explained in corrugated board grades for mailer boxes.

Box compression test (BCT; ISO 12048; ASTM D642; DE Stauchwiderstand)

The box compression test (BCT) loads an empty or filled box between two flat platens until it collapses, recording the peak force in newtons or lbf and the deflection at failure, under methods such as ISO 12048, ASTM D642 and TAPPI T804. It is the most direct measure of how a box behaves at the bottom of a stack. BCT depends on board ECT, caliper and box dimensions, and laboratory values must be reduced by safety factors for humidity, time and pallet pattern.

Box maker's certificate (BMC)

A box maker's certificate is the round stamp printed on North American corrugated boxes that names the box manufacturer and states either the minimum burst test and combined weight of facings or the minimum edge crush test, together with gross weight and size limits. It shows which certification route under UFC Rule 41 or NMFC Item 222 the box meets. Boxes made for the European market do not normally carry an equivalent mark.

Burst and ECT certification (UFC Rule 41; NMFC Item 222)

UFC Rule 41 (rail freight) and NMFC Item 222 (motor freight) are North American carrier classification rules that set minimum constructions for corrugated boxes by gross weight and size. Each allows two routes: a burst (Mullen) route with minimum combined facing weights, or an edge crush test route. The ECT route generally permits lighter or recycled-content board that still stacks well, while the burst route favours strong, heavy liners.

See: corrugated board grades for mailer boxes

Caliper loss (board crush)

Caliper loss is the reduction in corrugated board thickness caused by crushing the flutes, during converting through feed and nip rolls on printing and die-cutting machines or later through strapping and stacking. It is measured by comparing the caliper of converted blanks with the board as produced; a small loss is normal, but larger losses reduce ECT, BCT and cushioning even when the paper make-up is correct. Flexo post-printing and tight feed settings are common causes.

Concora medium test (CMT; ISO 7263; TAPPI T809)

The Concora medium test (CMT) measures the flat crush resistance of corrugating medium by fluting a strip of the paper in a laboratory corrugator, fixing it to tape and crushing it flat, reporting the force in newtons. It indicates how well the fluting paper will resist flute crush in combined board. CMT is a paper-mill and incoming-material test rather than a box specification value.

Edge crush test (ECT; ISO 3037; TAPPI T811; DE Kantenstauchwiderstand)

The edge crush test (ECT) measures the force needed to crush a short strip of combined corrugated board standing on its edge with the flutes vertical, reported in kN/m under ISO 3037 or lb/in under TAPPI T 811. One lb/in is about 0.175 kN/m, so the common US 32 ECT grade is about 5.6 kN/m. ECT is the best single predictor of a box's stacking strength and the main input to the McKee formula.

See: corrugated board grades for mailer boxes

Flat crush test (FCT; ISO 3035; TAPPI T808)

The flat crush test (FCT) measures the pressure needed to crush single-wall corrugated board flat between parallel plates, reported in kPa under ISO 3035 or TAPPI T808. It shows flute strength and how well the board resists crushing in printing, die-cutting and use; low values usually point to weak fluting paper or flutes damaged on the corrugator. FCT matters most for printed, die-cut boxes that pass through several nip points.

McKee formula

The McKee formula estimates the compression strength of a regular slotted corrugated box from board edge crush, board caliper and box perimeter; the simplified form is BCT ≈ 5.87 × ECT × √(caliper × perimeter) in imperial units. It shows that doubling ECT roughly doubles BCT and that thicker board raises BCT at the same ECT. It is an estimate for regular boxes, and die-cut styles, vents and handholes change the result, so critical designs are tested as finished boxes.

See: corrugated board grades for mailer boxes

Pin adhesion test (PAT; TAPPI T821)

The pin adhesion test measures the force needed to separate a liner from the fluting of corrugated board, using rows of pins inserted between the flutes and pulled apart in a compression tester, as described in TAPPI T821. Results are stated as force per length of glue line. Low values indicate weak starch bonds from the corrugator, which show as delamination, lower stiffness and reduced ECT and BCT.

Ring crush test (RCT; ISO 12192; TAPPI T822)

The ring crush test (RCT) measures the edgewise compression strength of a strip of paper or board formed into a ring and loaded on edge between platens, reported in kN/m. It is used for linerboard, fluting and solid board as an input to estimates of combined-board ECT. RCT is sensitive to sample thickness and has been largely replaced by SCT for grading containerboard in Europe.

Short-span compression test (SCT; ISO 9895; TAPPI T826)

The short-span compression test (SCT) measures the edgewise compression strength of liner or fluting over a free span of only 0.7 mm, which prevents buckling, and reports it in kN/m in machine and cross direction under ISO 9895 or TAPPI T826. Cross-direction SCT of the liners and fluting is the best paper-level predictor of combined-board ECT. Containerboard grades, including kraftliner and testliner classes, are commonly specified by SCT.

Stacking safety factor

A stacking safety factor is the ratio between a box's tested compression strength and the load it will carry at the bottom of a stack in use. It allows for humidity, storage time and creep, pallet pattern and overhang, handling damage and variation between boxes; factors of around 3 to 5 are commonly used for warehouse storage, with higher values for humid or long storage. Specifying a BCT figure without a safety factor is a common cause of collapsed pallets.

Transit and distribution tests

Tests on filled packages that simulate handling, vehicle transport and climate. They show how a pack and its contents survive the real route, which board and paper tests alone cannot.

ASTM D4169 (distribution cycle testing)

ASTM D4169 is a US standard practice for performance testing of shipping containers and systems that builds a laboratory test sequence, called a distribution cycle, from handling, stacking, vibration, impact and climatic elements. Assurance levels set the severity of each element. A result only has meaning when the distribution cycle and assurance level used are stated alongside it.

Climatic conditioning for transit tests (ISO 2233)

Transit tests often start by conditioning packages in a hot and humid, cold or cyclic climate, as described in ISO 2233 and in ISTA procedures, because paper and corrugated lose strength in humidity and adhesives and films behave differently in heat and cold. Export shipments in sea containers can see wide swings in humidity and condensation, so the climate should reflect the actual route. Tests at standard laboratory climate alone tend to overstate real performance.

See: sourcing packaging from Türkiye

Compression and stacking test (filled packages; top-load)

A stacking test applies a constant load to a filled package or unit load for an extended period, from hours to weeks, to see whether it deforms or collapses through creep, while a compression test raises the load until failure; ISO 12048 covers both. Stacking tests can be run in humid or cyclic climates to mimic warehouses and containers. They reveal problems that a short BCT misses, such as boxes that pass the peak load test but bulge after days in a humid store.

Drop test (free-fall drop; ISO 2248; ASTM D5276; DE Fallprüfung)

A drop test releases a filled package from a set height onto a rigid surface, on specified faces, edges and corners in sequence, and then checks package and product for damage. ISO 2248 and ASTM D5276 describe the method, while ISTA procedures and ASTM D4169 set the drop heights, which typically decrease as package weight rises. It is the core test for parcel and e-commerce shipments, where individual handling involves repeated drops.

ISTA test procedures (ISTA series)

The International Safe Transit Association (ISTA) publishes pre-shipment test procedures grouped into series: series 1 non-simulation integrity tests, series 2 partial simulation, series 3 general simulation, series 4 enhanced simulation, series 6 member-specific tests such as those set by large retailers and carriers, and series 7 development tests. Higher series reproduce real distribution more closely and cost more to run. Specifications should name the exact procedure and version, because each fixes its own conditioning, drop heights and vibration profiles.

ISTA 1A

ISTA 1A is a non-simulation integrity test for individual packaged products of 68 kg (150 lb) or less, combining fixed-displacement vibration with a series of drops from a height set by package weight. It is a basic screening test that shows whether pack and product survive rough handling, but it does not simulate a particular distribution environment. It is often used as a minimum check for goods shipped as parcels.

ISTA 3A

ISTA 3A is a general simulation test for packaged products of 70 kg (150 lb) or less shipped individually through parcel delivery systems, with variants for standard, small, flat and elongated packages. It combines atmospheric conditioning, random vibration, a sequence of drops and, depending on package type, impact tests, in an order designed to reproduce parcel hazards. It is a common benchmark for e-commerce packaging, including mailer boxes.

See: custom printed mailer boxes

Vibration test (random and sine; ISO 13355; ASTM D4728)

A vibration test shakes a packaged product on a table to reproduce vehicle transport, either with a random profile representing truck, rail or air transport (ISO 13355, ASTM D4728) or with fixed or swept sine vibration to find resonances. It reveals scuffing of print, loosening of closures, settling of contents and fatigue of corrugated boxes. A top load is often applied to represent the packages above in a stack.

Film and flexible packaging tests

Tests for plastic films, laminates, bags and pouches. Laminate structures and barrier values are explained in pouch laminate structures and barrier properties, and film units in plastic bag thickness: micron, gauge and mil.

Bond strength (laminate bond; ASTM F904; DE Verbundhaftung)

Bond strength is the force needed to peel apart the layers of a laminate, measured on strips, typically 15 mm or 25 mm wide, in a tensile tester and reported in N/15 mm or similar units; ASTM F904 describes one method. Low bond strength leads to delamination, tunnelling and seal failure, especially after hot filling or contact with aggressive products. Values are tested after the adhesive has fully cured, because laminates gain bond strength over days.

See: pouch laminate structures and barrier properties

Burst and creep test (pouches; ASTM F1140; ASTM F2054)

Pouch burst and creep tests inflate a sealed pouch with air and either raise the pressure until it fails (burst) or hold a set pressure for a fixed time to see whether seals peel open (creep). ASTM F1140 covers unrestrained pouches, and ASTM F2054 restrains the pouch between plates so that stress acts more evenly on all seals. Because they test every seal of the finished pack at once, they complement strip seal-strength results.

Coefficient of friction (COF; ASTM D1894; ISO 8295; DE Reibungskoeffizient)

The coefficient of friction (COF) is the ratio of the force needed to slide one surface over another to the force pressing them together, measured as static COF (starting) and kinetic COF (sliding) with a weighted sled under ASTM D1894 or ISO 8295. Films are tested film-to-film or film-to-metal, and values typically range from about 0.1 for slippery films to 0.5 or more for grippy ones. COF must suit the packing line: too high and film drags on forming parts, too low and bags and pouches slide off stacks and pallets.

Dart impact (falling dart; ASTM D1709; ISO 7765-1)

Dart impact strength is the weight of a falling hemispherical dart, dropped from a set height, that breaks 50 % of the film specimens tested, reported in grams under ASTM D1709 or ISO 7765-1. It reflects the film's toughness against sudden impacts and punctures, for example from the corners of boxed goods in a carrier bag. LLDPE and metallocene grades raise dart impact compared with plain LDPE or HDPE at the same thickness.

Dyne level (surface energy; wetting tension; ISO 8296; ASTM D2578)

The dyne level is the surface energy of a plastic film, measured by applying test inks of known surface tension (ISO 8296, ASTM D2578) and finding the highest value that wets the surface without beading, in mN/m or dyn/cm. Untreated polyethylene is typically around 30-31 mN/m, too low for inks and adhesives to wet, so films are corona or flame treated, commonly to about 38-42 mN/m or higher for printing and lamination. Treatment decays in storage, so the level is checked shortly before printing.

See: printing plastic bags

Elongation at break (film)

Elongation at break is the percentage by which a film specimen stretches before it breaks in a tensile test under ASTM D882 or ISO 527-3, reported for machine and cross direction. Blown polyethylene films typically elongate by several hundred per cent, while oriented films such as BOPP and PET stretch much less. Together with tensile strength, it indicates toughness and how a bag behaves when overloaded or snagged.

Haze and gloss (ASTM D1003; ASTM D2457; ISO 2813)

Haze is the percentage of transmitted light scattered by more than 2.5° as it passes through a film, measured to ASTM D1003, so low haze means a clear, see-through film for windows, lids and display bags. Gloss is the specular reflectance of a surface measured with a glossmeter at a set angle, typically 20°, 45° or 60°, in gloss units under ASTM D2457 for plastic films or ISO 2813 for coatings. Gloss values are only comparable at the same angle, and both properties depend on polymer grade, additives and processing.

Heat seal range (seal window; seal curve)

The heat seal range, or seal window, is the span of sealing temperatures, at a given pressure and dwell time, over which a film or coating forms an acceptable seal without burning, distorting or delaminating. It is found by plotting seal strength against sealing temperature in a seal curve. A wide window tolerates variation on packing lines, and a low seal initiation temperature allows faster running.

Heat seal strength (seal strength; ASTM F88; DE Siegelnahtfestigkeit)

Heat seal strength is the force needed to peel apart a heat seal, measured by pulling a strip cut across the seal in a tensile tester under ASTM F88 and reported in N/15 mm in Europe or lbf/in in the US. The failure mode, such as peel, delamination or tear of the material beside the seal, is recorded with the value, because a strong but brittle seal can still fail. It is specified for bags, pouches, lidding films and coated paper seams.

See: pouch features

Hot tack (ASTM F1921)

Hot tack is the strength of a heat seal while it is still molten or hot, measured by pulling the seal apart a fraction of a second after the sealing jaws open, as described in ASTM F1921. It matters on vertical form-fill-seal and other high-speed lines, where the product falls onto the bottom seal before it has cooled. Sealant layers with good hot tack, such as metallocene polyethylene, allow faster filling.

Leak test (bubble emission; vacuum decay; dye penetration)

Leak tests check whether a sealed pack has holes or channels that let air or liquid through. Bubble emission immerses the pack in water under vacuum and watches for bubbles (ASTM D3078), dye penetration runs a coloured solution along seals to reveal channels, and vacuum decay measures pressure change in a test chamber without destroying the pack. Leak tests find defects that strip seal-strength tests miss, such as a wrinkle or pinhole in an otherwise strong seal.

OTR (oxygen transmission rate; ASTM D3985; ISO 15105-2)

OTR (oxygen transmission rate) is the volume of oxygen passing through a square metre of film or laminate in 24 hours, measured with a coulometric sensor under ASTM D3985 or ISO 15105-2 and reported in cm³/(m²·day·atm) at stated temperature and humidity. Values range from thousands for thin plain polyolefin films to below 1 for foil and high-barrier structures. Figures are only comparable at the same temperature, humidity and thickness, and some barrier polymers, notably EVOH, lose performance at high humidity.

See: pouch laminate structures and barrier properties

Puncture resistance (film)

Puncture resistance is the force and energy needed to push a probe through a film or laminate at slow speed, measured on a tensile tester with a defined probe, for example under ASTM F1306. It complements dart impact, which uses a fast falling weight, and is specified where pouches and bags hold sharp or hard products such as pasta, nuts, bones or frozen food. Thicker films, polyamide layers and tough sealants raise puncture resistance.

Residual solvent test

A residual solvent test measures traces of printing and laminating solvents, such as ethyl acetate or ethanol, left in a printed film or laminate, usually by headspace gas chromatography with results in mg/m². Excess residual solvent causes odour, taint and blocking and can affect food-contact compliance. Converters commonly set internal limits, and food brands may set stricter ones for sensitive products.

Tensile strength (film; ASTM D882; ISO 527-3)

Film tensile strength is the maximum stress a thin plastic strip withstands when pulled in a tensile tester, reported in MPa under ASTM D882 for sheeting less than 1 mm thick or ISO 527-3 for films. It is measured in machine and cross direction together with elongation at break and modulus, which expresses stiffness. Tensile values show whether bag handles, pouch walls and film webs can carry the loads of use and converting.

Thickness (film; ISO 4593)

Film thickness is measured with a mechanical micrometer to ISO 4593 or, on production lines, with non-contact gauges scanning across the web, and is stated in µm, mil or UK gauge. Both average thickness and the variation across the web matter, because thin spots fail first and thick lanes cause gauge bands and creases on rolls. Thickness thresholds also decide how plastic carrier bags are treated under several bag laws.

See: plastic bag thickness: micron, gauge and mil

WVTR (water vapour transmission rate; ASTM F1249; ISO 15106)

WVTR (water vapour transmission rate) is the mass of water vapour passing through a square metre of material in 24 hours, in g/(m²·day), measured with sensors under ASTM F1249 or the ISO 15106 series, or gravimetrically by the dish method of ISO 2528 for paper and other sheet materials. Tests run at stated conditions, typically 38 °C/90 % RH or 23 °C/85 % RH, and values from different conditions are not interchangeable. WVTR decides how long dry foods stay crisp and how well moist foods keep their weight.

Cup and container tests

Functional tests for paper cups, food containers and their lids, ideally with the real product at real temperature. Linings are compared in paper cup linings and hot-food use in paper soup containers.

Capacity check (brim-full and fill-line volume)

A capacity check measures the volume a cup or container holds when filled to the brim and to its nominal fill line, usually by weighing water at a known temperature. Nominal sizes such as 12 oz are labels, so specifications should state brim-full volume with a tolerance and, where relevant, the fill line. Capacity varies with forming settings, wall construction and out-of-roundness, so it is checked at first-article inspection and during production.

See: paper cup sizes

Hot-fill test

A hot-fill test fills cups or containers with hot water, or the actual drink or food, at the intended serving temperature, typically somewhere between about 70 °C and 95 °C, and holds them for the expected service time while checking for leaks, softening, seam opening, odour and loss of rigidity. It is the practical check for PE-lined and dispersion-coated cups, soup containers and their lids. Fill temperature, hold time and whether lids and stacking are included must be fixed in the specification, because each changes the result.

See: paper soup containers

Leak test (cups and containers)

A cup or container leak test fills samples with water, often dyed or with a wetting agent to reveal fine leaks, and holds them for a set time upright and sometimes tilted or under load, checking side seam, bottom seal and sidewall for drips or staining. Testing with the real product at serving temperature is more reliable than cold water alone, because fat, acids and heat attack seams and coatings differently. Leaking units are normally classed as critical or major defects.

Lid fit test

A lid fit test checks that a lid snaps onto the matching cup or container rim, seals all round and stays on when the pack is tilted, squeezed or carried, sometimes with a filled pack held inverted. Fit depends on the rim diameter and rim profile of the cup as well as on the lid's own tolerances, so cups and lids from different suppliers must be tested together. Specifications should name the lid and test the pair rather than each part separately.

See: lids for paper food containers

Lid removal force (pull-off force)

Lid removal force is the force needed to pull or peel a lid off a cup or container, measured with a force gauge or tensile tester attached to the lid tab or edge. If it is too low, lids come off in delivery; if it is too high, customers squeeze the cup and spill hot drink. It is best checked on filled, warm packs because heat and steam change the fit.

Rim strength (rim roll; rim crush)

Rim strength is the resistance of a cup's rolled rim to being crushed or distorted, tested by applying a vertical or radial load to the rim. The rim roll stiffens the mouth of the cup and is what the lid locks onto, so a weak, uneven or incompletely curled rim leads to poor lid fit, leaks at the lid and cups that collapse when gripped. Rim diameter and roundness are measured alongside strength.

Sidewall rigidity (squeeze test; top-load test)

Sidewall rigidity is the resistance of a cup or container wall to inward pressure, measured by pressing a probe against the wall at a set height and recording force at a given deflection, while a top-load test presses down on the rim to check stacking and lidding strength. Rigidity depends on board grammage and stiffness, wall construction and forming quality. Low rigidity shows as cups that buckle when held full of hot coffee or rims that deform when lids are pressed on.

See: single vs double vs ripple wall cups

Print quality and ink resistance tests

Measurements used to approve and control printed colour and to check that print survives handling, moisture and light. Print processes and print defects are defined in the printing and prepress glossary.

Barcode verification (ISO/IEC 15416)

Barcode verification grades the print quality of a linear barcode with a verifier that measures parameters such as edge contrast, modulation and decodability and gives an overall grade from A to F under ISO/IEC 15416, with ISO/IEC 15415 used for 2D codes. GS1 guidance for retail EAN/UPC symbols commonly calls for grade C (1.5) or better. Flexo printing on kraft or corrugated, bar width reduction and the choice of bar and background colours all affect the grade.

Delta E (ΔE; ΔE00, CIEDE2000; DE Farbabstand)

Delta E (ΔE) expresses the difference between two colours as a single number calculated from spectrophotometer measurements in the CIELAB colour space; lower values mean a closer match. Packaging tolerances are agreed between buyer and printer, often around 2-4 ΔE00 for spot colours, and the formula (ΔE76 or CIEDE2000), illuminant, observer and measurement condition (M0 to M3 under ISO 13655) must be stated because each changes the number. A ΔE tolerance only has meaning against an agreed physical or numeric reference.

See: Pantone vs CMYK in packaging

Dot gain (tone value increase, TVI; DE Tonwertzunahme)

Dot gain, or tone value increase (TVI), is the amount by which halftone dots print larger than they are in the file, measured with a densitometer or spectrophotometer as the difference in tone value, often at the 50 % patch. It is higher on absorbent and rough substrates such as uncoated kraft and in flexo printing, and prepress compensates for it with tone curves. Uncontrolled dot gain darkens images, fills in shadows and shifts colour.

See: printing and prepress glossary

Ink drawdown (draw-down)

An ink drawdown is a thin, even film of ink spread on the actual substrate with a hand roller or wire bar, used to approve a spot colour before the production run. Because the same ink looks different on white board, kraft and film, a drawdown on the production material is a better colour reference than a printed swatch book. Drawdowns are measured with a spectrophotometer and kept as part of the colour standard.

Light fastness (ISO 12040; Blue Wool Scale; DE Lichtechtheit)

Light fastness is the resistance of printed colour to fading under light, tested by exposing prints to filtered xenon-arc light alongside Blue Wool reference strips as described in ISO 12040, and rated on the Blue Wool Scale from 1 (very poor) to 8 (excellent). It matters for displays, window packaging and items stored under strong light, where fluorescent and some bright pigments fade first. Short-life foodservice packaging rarely needs high ratings.

Registration tolerance (DE Passer)

Registration tolerance is the permitted misalignment between printing colours (colour-to-colour register) or between print and the cut, crease or fold (print-to-cut register), usually stated in millimetres. Achievable values depend on process and substrate: sheet-fed offset on board holds tighter register than flexo on kraft paper, film or corrugated board, where materials stretch and move. Trapping and safe zones in artwork are designed around the tolerance the process can hold.

See: packaging artwork preparation

Resistance of prints to agents (ISO 2836)

ISO 2836 describes tests of how prints and printing inks resist specific agents such as water, fats and oils, acids, alkalis, detergents and solvents, by contact with the agent or with filter paper soaked in it, followed by assessment of bleeding or colour change. It is used to check that print on food packaging will not bleed when the pack becomes wet or greasy or is wiped. Results are rated against a grey scale or as pass or fail.

Rub and scuff resistance (Sutherland rub test; ASTM D5264; DE Scheuerfestigkeit)

Rub resistance is the ability of printed ink to withstand abrasion, tested by rubbing a printed sample against a receptor sheet under a weighted block for a set number of strokes on a Sutherland-type rub tester (ASTM D5264) and assessing ink loss and transfer. Scuff resistance describes the same property in use, when cartons, sleeves or bags rub against each other in cases and in transit vibration. Dark solids, matt finishes and uncoated kraft scuff most visibly, and varnishes, harder inks and full curing improve results.

See: carton finishes

Solid ink density (densitometry)

Solid ink density is the light-absorbing strength of a printed solid patch, measured with a densitometer through the filter matching each process colour and expressed in density units. It is the press operator's main control for ink film thickness: too low looks washed out, while too high raises dot gain, set-off and drying problems. Density targets differ by process, ink set and substrate, so they are agreed per job or taken from process standards such as the ISO 12647 series.

Tape adhesion test (ink adhesion; ASTM F2252)

A tape adhesion test presses a standard pressure-sensitive tape onto printed or coated film or board and pulls it off quickly, then assesses how much ink or coating has come away; ASTM F2252 describes the method for flexible packaging. It is the routine check of ink adhesion on plastic films, where poor corona treatment or unsuitable inks show as ink lifting. Results are reported as the percentage removed or on a rating scale.

See: printing plastic bags

Food-contact and chemical testing

Laboratory tests that support food-contact declarations and chemical requirements. The legal framework is set out in food-contact packaging compliance in the EU, UK and US and PFAS rules in PFAS-free food packaging; the definitions below describe the tests, not legal obligations.

Food simulant (DE Lebensmittelsimulanz)

A food simulant is a test medium that stands in for food in migration testing. Regulation (EU) 10/2011 defines simulants A (10 % ethanol), B (3 % acetic acid), C (20 % ethanol), D1 (50 % ethanol), D2 (vegetable oil) and E (poly(2,6-diphenyl-p-phenylene oxide), known as MPPO or by the trade name Tenax, for dry foods) and assigns them to food categories. Choosing simulants and test conditions that reflect the real food, temperature and contact time is what makes a migration result relevant.

Heavy metals test (lead, cadmium, mercury, hexavalent chromium)

A heavy metals test measures lead, cadmium, mercury and hexavalent chromium in packaging or its components, such as inks and pigments, typically by ICP spectrometry after digestion, with a separate method for hexavalent chromium. EU packaging law has long limited the sum of these four to 100 mg/kg, a requirement carried into the PPWR, and several US states apply similar limits through toxics-in-packaging laws. Results are usually supplied as a laboratory report or supplier declaration on request.

Mineral oil analysis (MOSH/MOAH testing)

Mineral oil analysis measures mineral oil saturated and aromatic hydrocarbons (MOSH and MOAH) in packaging or food, usually by online coupled liquid and gas chromatography with flame ionisation detection (LC-GC-FID), reporting results in mg/kg for defined carbon-number ranges. Carbon range matters because volatility decides what can migrate through the gas phase. There is no binding EU limit for packaging as of October 2026, so results are compared with customer specifications, and testing the food after storage can be more informative than testing the board.

See: mineral oil barriers and food-safe cartons

NIAS (non-intentionally added substances)

NIAS are substances present in a food-contact material that were not added on purpose, such as impurities in raw materials, reaction and breakdown products and contaminants from recycling. Regulation (EU) 10/2011 requires them to be assessed for plastics, and screening analysis, often by gas or liquid chromatography with mass spectrometry, is used to find and identify them. NIAS assessment is increasingly expected for inks, adhesives, coatings and recycled materials as well.

Odour test (EN 1230-1)

An odour test is a sensory assessment of the smell given off by a packaging material, in which a trained panel rates the odour intensity of samples enclosed in jars for a set time, as described in EN 1230-1 for paper and board. It catches residual solvents, ink odour, oxidised coatings and recycled-fibre odours that chemical tests may not flag. Odour tests are common for cups, coffee, tea and confectionery packaging.

Overall migration (OM; overall migration limit, OML)

Overall migration is the total mass of non-volatile substances a material releases into a food simulant under test conditions, reported in mg/dm² of contact surface. Regulation (EU) 10/2011 sets an overall migration limit (OML) of 10 mg/dm² for plastic food-contact materials and plastic layers, tested under standardised time and temperature conditions (OM1 to OM7) chosen to cover the intended use. Overall migration measures inertness, not toxicity, and is always complemented by specific migration checks.

See: food-contact packaging compliance

PFAS targeted analysis

Targeted PFAS analysis measures a defined list of individual PFAS, usually by liquid chromatography with tandem mass spectrometry (LC-MS/MS), reporting each compound in µg/kg (ppb). Under Regulation (EU) 2025/40, food-contact packaging placed on the EU market from 12 August 2026 must stay below 25 ppb for any single PFAS and 250 ppb for the sum of PFAS measured by targeted analysis. Results cover only the compounds on the list, so the laboratory's analyte list and reporting limits must be checked.

See: PFAS-free food packaging

Specific migration (SML)

Specific migration is the amount of one named substance transferring from a material into food or a food simulant, reported in mg/kg of food. Regulation (EU) 10/2011 sets specific migration limits (SMLs) for listed substances such as certain monomers and additives, and compliance can be shown by migration testing, by calculation from residual content or by modelling. A Declaration of Compliance should identify substances with SMLs so that the filler can verify them for the final food.

Taint test (off-flavour; EN 1230-2; Robinson test)

A taint test checks whether a packaging material transfers an off-flavour to food by storing a sensitive test food with the material in a closed container and having a trained panel compare it with a control; EN 1230-2 describes the method for paper and board, typically with chocolate as the test food in the Robinson-type test. Fatty, mild-flavoured foods such as chocolate, butter, coffee and baked goods are the most sensitive. DIN 10955 is a related German method for sensory testing of packaging materials.

Total fluorine (TF) and total organic fluorine (TOF)

Total fluorine is a screening measurement of all fluorine in a material, organic and inorganic, usually by combustion ion chromatography, reported in mg/kg (ppm); total organic fluorine (TOF) excludes inorganic fluoride. Under the PPWR, total fluorine above 50 mg/kg triggers a duty to show whether the fluorine comes from PFAS (the limit itself is 50 ppm for all PFAS including polymeric PFAS), and several US states and BPI compostability certification use about 100 ppm TOF as an indicator. A total fluorine result cannot identify individual PFAS.

See: PFAS-free food packaging

Worst-case testing (conditions of use)

Worst-case testing means choosing the most severe realistic conditions of use (the most aggressive food type, the highest temperature and the longest contact time) so that one test result also covers milder uses. A container tested at hot-fill temperature with the relevant simulants can cover the same foods served cold, but a cold test does not cover hot use. Declarations of Compliance state the conditions tested, which in turn limit how the packaging may be used.

Quality systems, sampling and documents

Terms for approving, inspecting and documenting packaging and handling problems. The process from samples to complaints is described step by step in packaging sampling and quality control.

8D report (eight disciplines)

An 8D report is a structured problem-solving format from the automotive industry that works through eight disciplines: forming a team, describing the problem, containment, root cause analysis, choosing permanent corrective actions, implementing and verifying them, preventing recurrence and closing the case. Buyers often request an 8D for serious or repeated complaints because it separates immediate containment from the lasting fix. A useful 8D includes evidence such as data, photos and changed work instructions rather than statements alone.

Acceptance and rejection numbers (Ac/Re)

The acceptance number (Ac) is the maximum number of defective units allowed in an AQL sample for the lot to be accepted, and the rejection number (Re) is the number at which the lot is rejected. Both come from the ISO 2859-1 tables for the sample size code letter and the agreed AQL. For example, a lot of 50,000 units at general inspection level II gives code letter N and a sample of 500; at AQL 2.5 the lot is accepted with up to 21 defectives and rejected at 22, and at AQL 1.0 the numbers are 10 and 11.

AQL (acceptance quality limit; ISO 2859-1; ANSI/ASQ Z1.4)

AQL (acceptance quality limit) sampling inspects a random sample from a lot instead of every unit, using the tables of ISO 2859-1 or the closely equivalent US standard ANSI/ASQ Z1.4. Lot size and inspection level set the sample size, and the AQL agreed for each defect class sets the acceptance and rejection numbers. An AQL describes the worst tolerable average defect level over a series of lots, not a guarantee for any single lot, and buyers commonly use zero tolerance for critical defects, about 1.0-2.5 for major and 2.5-4.0 for minor defects.

See: packaging sampling and quality control

Batch traceability (lot traceability; DE Rückverfolgbarkeit)

Batch traceability is the ability to link a delivered unit or case, through its lot code, to the production run, the material and ink batches used, the machine and the production date. Regulation (EC) 1935/2004 Article 17 requires traceability of food-contact materials at all stages in the EU, and consistent lot coding makes complaint investigation, recalls and retained-sample checks possible. Lot codes on cases and pallet labels are the minimum, and codes on the item itself help where cases are discarded in stores.

CAPA (corrective and preventive action)

CAPA is the process of removing the cause of a non-conformance (corrective action) and preventing similar problems elsewhere (preventive action), documented with root cause, actions, owners, deadlines and a check of effectiveness. It is a core element of quality management systems. A CAPA should be closed only when evidence shows the problem has not recurred, not when the action has merely been agreed.

Certificate of Analysis (CoA)

A Certificate of Analysis (CoA) is a document issued for a specific lot that reports measured test results, such as grammage, caliper, moisture, Cobb, KIT or seal strength, against the specification limits. It is usually issued by the manufacturer's laboratory, or by an external laboratory where required. A CoA is evidence for that lot only and does not replace a Declaration of Compliance or periodic external testing.

Certificate of Conformance (CoC; certificate of conformity)

A Certificate of Conformance (CoC) is a supplier's statement that a delivered lot was produced to the agreed specification and drawings, usually without listing individual test results. It is lighter than a CoA and common where the buyer relies on the supplier's quality system. In packaging, CoC also abbreviates chain of custody in FSC and PEFC certification, so documents should spell the term out.

Concession (deviation approval)

A concession is the buyer's written agreement to accept product that does not fully meet the specification, for a defined quantity or period, for example a lot with a slight colour shift that is still usable. It avoids rejecting usable goods, but it should be recorded, limited in scope and linked to a corrective action so that the deviation does not quietly become the new standard.

Critical, major and minor defects (defect classification; DE kritischer Fehler, Hauptfehler, Nebenfehler)

Defect classification sorts inspection findings by consequence: critical defects make a product unsafe, non-compliant or harmful to the user, such as contamination or a leaking hot-drink cup; major defects make it unusable or likely to fail in use, such as an open glue seam or a missing handle; minor defects are cosmetic and do not affect function. Each class has its own AQL, tightest for critical defects. A defect list with photos and agreed classes belongs in the specification.

See: packaging sampling and quality control

Declaration of Compliance (DoC; food contact)

A Declaration of Compliance (DoC) is the written statement in which a supplier confirms that a food-contact material complies with the applicable rules for stated conditions of use, such as food types, temperature and contact time, and identifies substances subject to migration limits. It is legally required for plastics under Regulation (EU) 10/2011 at each marketing stage other than retail and is expected by buyers for paper and board. It is a different document from the PPWR EU Declaration of Conformity and from a CoA.

See: food-contact packaging compliance; PPWR Declaration of Conformity

First-article inspection (FAI; DE Erstmusterprüfung)

First-article inspection is a complete check of the first units from a new tool, process or job against every requirement in the drawing and specification, covering dimensions, material, print, function and documents. In packaging it typically follows the set-up of a new cutting die, cup mould or print job and is signed off before the rest of the run continues. The FAI report records each measured value against its tolerance and becomes a reference for later lots.

Golden sample (master sample; DE Referenzmuster)

A golden sample is the approved, signed physical sample against which production and inspections are measured. It should exist in at least two sets, one held by the buyer and one by the manufacturer, ideally with a third for an inspection agency, and be stored away from light and humidity because paper and print change over time. When the design or specification changes, the golden sample is replaced rather than altered.

See: packaging sampling and quality control

In-process control (IPC; control plan)

In-process control is the set of checks made by operators and quality staff during production, such as colour readings, register, glue presence, dimensions, seal strength and counts, at defined frequencies. It catches drift before a whole lot is affected, which makes it more effective than final inspection alone. A control plan lists each check with its frequency, method, limit and the reaction if a result falls outside the limit.

Inspection level (general I, II, III; special S-1 to S-4)

The inspection level in ISO 2859-1 sets how large the sample is for a given lot size: general levels I, II and III, with II as the usual default, level I giving smaller samples and level III larger ones. Special levels S-1 to S-4 use very small samples and suit destructive, slow or expensive tests such as burst, leak or seal tests. The level, like the AQL, is agreed before inspection.

Limit sample (boundary sample; DE Grenzmuster)

A limit sample shows the worst acceptable condition of a visual characteristic, such as the lightest acceptable colour, the largest allowed spot or the strongest acceptable washboarding. Limit samples, often kept as a pair of just-acceptable and just-rejectable examples, make visual inspection less subjective than written descriptions. They are especially useful for shade on kraft and recycled board and for cosmetic print defects.

Non-conformance report (NCR; non-conformance)

A non-conformance is any failure of product or process to meet a specified requirement, recorded in a non-conformance report (NCR) with lot, quantity, evidence and classification. The NCR triggers containment, meaning immediate action such as quarantining or sorting stock to stop bad product reaching use, followed by root cause analysis and CAPA, and it is the basis for any credit, rework or replacement. A buyer's complaint to a supplier, a Reklamation in German, usually opens one.

PPAP-style approval (production part approval)

A PPAP-style approval adapts the automotive Production Part Approval Process to packaging: before series supply, the supplier submits a package of evidence, typically drawings and dieline, material specifications and declarations, test results, first-article measurements, process flow, control plan and approved samples, and the buyer signs it off. Large chains and brand owners use it for new items and major changes. A later change of material, mill, site or tooling normally triggers a new approval.

Pre-production sample (PPS)

A pre-production sample (PPS) is a printed sample made with the buyer's artwork on the intended material before the main run, used to approve appearance, print and function. If it is made by a different process from production, for example digital instead of flexo, its colour can differ from the final run, so colour-critical jobs add an ink drawdown or press proof. The signed PPS, or a production sample approved after it, usually becomes the golden sample.

See: packaging sampling and quality control

Pre-shipment inspection (PSI; final random inspection)

A pre-shipment inspection is an AQL-based inspection of finished, packed goods, carried out by the buyer's staff or a third-party agency before goods leave the factory, typically when most of the order, often 80 % or more, is packed. It checks quantity, packing, case marking, appearance and function against the specification and golden sample. A PSI cannot find defects that only appear in use, so it is combined with functional tests such as leak, load or drop tests.

Retained samples (retention samples; DE Rückstellmuster)

Retained samples are units kept from each production lot for a defined period so that any later complaint can be checked against what was actually produced. They are stored with their lot identification in conditions that do not change them, and the retention period usually covers the shelf life of the packed product with a margin or a contractual minimum. Combined with lot codes, they turn a complaint from an argument into a comparison.

See: packaging sampling and quality control

Root cause analysis (5 Whys; Ishikawa diagram)

Root cause analysis is the structured search for the underlying cause of a defect rather than its symptom, using tools such as the 5 Whys and the Ishikawa (fishbone) diagram, which groups possible causes under headings like material, machine, method, people, measurement and environment. In packaging, a recurring glue failure may trace back to board moisture, glue temperature or line speed rather than to the adhesive itself. The verified root cause is what a CAPA or 8D must address.

Specification sheet (technical specification)

A specification sheet is the agreed technical description of a packaging item: dimensions with tolerances, material grade and grammage, coatings, print process and colour references, finishes, required test values with methods, packing and labelling. It is the document that inspections, CoAs and complaints refer to, so anything missing from it is difficult to enforce. It carries a version number and is reissued, not edited informally, whenever something changes.

See: packaging RFQ guide

Statistical process control (SPC; Cpk)

Statistical process control (SPC) monitors a process by plotting measurements, such as grammage, seal strength or register, on control charts to separate normal variation from a real change. Process capability indices such as Cpk compare the spread and centring of the process with the specification tolerance; a Cpk of 1.33 or more is a common target, meaning the process fits comfortably within the limits. Capability data give more confidence over many lots than a single CoA value.

Switching rules (normal, tightened and reduced inspection)

Switching rules in ISO 2859-1 move inspection from normal to tightened after a set number of rejected lots, and from normal to reduced after a sustained record of accepted lots and stable production. Tightened inspection uses stricter acceptance numbers, while reduced inspection uses smaller samples. Buyers who apply only normal inspection lose part of the protection the scheme is designed to give over a series of lots.

Defects: paper bags

Defect names used in inspection checklists for SOS, flat and carrier bags. How bags are formed, and therefore where these defects arise, is described in how paper bags are made. Print defects that apply to all formats, such as misregistration, set-off and mottle, are defined in the printing and prepress glossary.

Bottom open (bottom seam failure)

A bottom open is a paper bag whose glued base opens or partly separates, either straight off the machine or when loaded. Causes include glue skips or too little glue, an adhesive unsuited to the paper or coating, poor fold pressure and paper moisture outside the agreed range. Because contents can fall out, open bottoms are classed as major or critical defects and are checked with a load test.

Glue skip (missing glue)

A glue skip is a gap in an adhesive line, on a bag side seam, bottom or handle patch or on a carton glue flap, where no glue was applied. It comes from clogged nozzles, worn glue wheels, splashing or interruptions at reel splices, and shows as seams that open or patches that peel. Glue detection systems on converting machines reject many skips, but sampling still checks seams by opening them by hand.

Gusset defects (off-centre or skewed gusset)

Gusset defects are bags whose side gussets are folded off-centre, uneven in depth or skewed, so the bag does not stand square, the front and back panels differ in width and print runs onto the gusset. They come from tube-forming settings and paper behaviour and affect how SOS bags open and stack in dispensers. Gusset depth is checked against the dimensional tolerance on the specification.

See: SOS bags explained

Handle pull-off (handle detachment)

Handle pull-off is the detachment of a twisted or flat paper handle from a loaded bag, either because the patch peels from the bag wall or because the handle tears out of the patch. Causes include insufficient or misplaced glue, weak patch or bag paper, handles set too close to the top fold and loads above the bag's design limit. It is checked with a static or dynamic handle load test at a defined weight, and failures are major defects.

See: paper bag handle types

Print-to-cut variation (cut-off variation)

Print-to-cut variation is movement of the printed design relative to the cut edges of a bag, so that logos sit higher or lower than approved or are cut through. On reel-fed bag machines it comes from paper stretch, registration control and variation in cut-off length, which also changes bag height. Tolerances are stated in millimetres and checked against the golden sample.

Tube misalignment (side seam offset)

Tube misalignment is an offset or skewed overlap of the longitudinal side seam formed when the paper web is folded into a tube, giving a crooked seam, a seam visible on the front panel or uneven gussets. It comes from web tracking, variation in paper width and folding settings. Severe misalignment weakens the seam and bottom and is conspicuous on printed bags.

Wrinkles and creases (tube wrinkles)

Wrinkles are unintended folds in the paper of a bag, typically along the tube, near the bottom or around handle patches, caused by uneven web tension, moisture or poorly set folding parts. Apart from their appearance, they disturb print, weaken glued areas and can stop bags opening properly in dispensers or on automatic bagging lines. Light wrinkles are minor defects, while wrinkles across glue lines are usually major.

Defects: cartons and corrugated boxes

Defect names for folding cartons, food boxes and corrugated boxes. Converting steps behind them are described in how folding cartons and food boxes are made and how corrugated packaging is made.

Crack at crease (crease cracking; fibre cracking)

Crease cracking is breakage of the coating, print or fibres along a fold line, showing as a white or brown line where a carton or box is bent. It comes from board that is too dry or too stiff for the crease, crease rules and channels not matched to board thickness, creases running the wrong way relative to the grain, or heavy ink and varnish on the fold. Cracks on visible panels are cosmetic or major depending on severity, while deep fibre cracks weaken the fold itself.

See: carton dielines, cutting dies and prototyping

Crush (box crush; flute crush)

Crush is local or overall flattening of corrugated board or boxes by feed rolls in converting, strapping, overloaded pallets or impacts in transit. Flute crush reduces caliper, stiffness and stacking strength, often without obvious visible damage, which is why caliper and flat crush are checked on converted blanks. Crushed corners and bowed panels on delivered boxes usually point to compression or handling problems rather than to board grade alone.

Delamination (ply separation)

Delamination is the separation of layers: liner from fluting in corrugated board, plies within carton board, film from board in laminated cartons or layers within a flexible laminate. It shows as blisters, loose liners at edges or peeling film and comes from weak bonding, moisture, heat or over-flexing at creases. Pin adhesion, internal bond and laminate bond strength tests measure the underlying strength.

Fibre dust and angel hair

Fibre dust and angel hair are loose fibres and thin strands of paper left on die-cut edges and inside boxes by dull knives, worn cutting rules, poor stripping or ragged nicks. They contaminate products, particularly food and electronics, and can lead to rejection under food-safety audits. Sharp tooling, effective stripping and dust extraction keep them under control.

Fishtail and gap variation (manufacturer's joint)

A fishtail is a folded box or carton whose panels are misaligned so that the edges at the closing end form a V instead of meeting squarely, and gap variation is a joint gap that is wider at one end than the other. Both come from skewed folding or gluing on the folder-gluer, inaccurate creasing or blanks cut out of square. They cause problems on automatic erecting and closing lines and can let glued joints open.

Glue failure (poor glue; pop-open)

Glue failure is a carton side seam, crash-lock base or box manufacturer's joint that opens, either immediately or later in storage or use; a pop-open is a glued joint that springs apart when the flat carton is erected. Causes include glue skips, too little or unsuitable adhesive, varnish or coating on the glue area, short compression time and board moisture. It is classed as a major defect and checked by tearing glued joints open, where fibre tear across the joint indicates a good bond.

Nick defects (ties too strong or too weak)

Nicks, or ties, are small uncut points in a cutting die that hold blanks in the sheet until stripping. Nicks that are too strong leave torn edges and fluff when blanks are broken out, while nicks that are too weak let blanks fall out early and jam the folder-gluer. Nick position also affects appearance, because each nick leaves a small mark on the finished edge.

Skewed fold (out-of-square folding)

A skewed fold is a fold line that runs at an angle to the intended crease, or a panel folded out of square, so that the carton or box does not form a true rectangle and closing flaps clash or gape. Causes include blanks misfed into the folder-gluer, creases not matched to the board and die-cutting out of register with print. Skew is measured as the difference between diagonals or as angular deviation on erected samples.

Warp (bow; twist; curl)

Warp is a deviation of a sheet, blank or corrugated board from flatness, showing as bow along or across the sheet, twist or S-shaped curl. In corrugated board it comes from moisture differences between the liners during and after corrugating; in carton board from uneven moisture or one-sided coatings and laminates. Warped blanks misfeed in printing, die-cutting, folder-gluers and automatic packing machines, so flatness is often specified as maximum deviation over a stated length.

Washboarding (DE Waschbretteffekt)

Washboarding is a visible ripple pattern on printed corrugated board where the liner follows the flutes beneath it, most noticeable with coarse flutes, light liners and dark or glossy solid print. It is a cosmetic defect assessed against a limit sample, because some ripple is normal for each flute. Finer flutes, heavier liners, pre-print or litho-lamination reduce it.

See: pizza box printing

Defects: cups and containers

Defect names for paper cups and round or square food containers. Forming and sealing are described in how paper cups and containers are made.

Bottom leak (bottom seal failure; knurl leak)

A bottom leak is liquid escaping through the joint between the bottom disc and sidewall of a cup or container, which is heat-sealed and then knurled under pressure to lock it. Causes include insufficient heat or pressure, off-centre bottom discs, coating defects at the seal and unsuitable board and coating combinations. Bottom leaks are critical or major defects for drinks and soups and are found by leak and hot-fill tests.

Coating defects (pinholes, cracks, voids)

Coating defects are breaks in the PE, PLA or dispersion barrier on cupstock and container board, such as pinholes, cracks at folds, voids and thin areas, which let liquid reach the fibre. They show as damp patches, staining or softening walls, often only after several minutes of contact with hot liquid. Dye penetration and hot-fill tests detect them.

See: paper cup linings

Leaking side seam (seam leak)

A leaking side seam is a cup or container that loses liquid along the vertical overlap where the sidewall blank is sealed into a cone, most often near the top or bottom end of the seam. Causes include poor heat sealing, edge wicking at the exposed board edge and misaligned blanks. Side seam leaks are tested with dyed water and with real drinks at serving temperature, and are major or critical defects.

Out-of-round (ovality)

An out-of-round cup or container has a rim or body that is oval instead of circular, measured as the difference between its largest and smallest diameters. It comes from forming, from storage under load or from humidity, and it stops lids fitting and sealing properly. Ovality is checked together with rim diameter against the lid's tolerances.

Rim defects (incomplete curl; cracked or split rim)

Rim defects are faults in the rolled rim of a cup or container, such as an incomplete or uneven curl, a crack where the board breaks during curling, a split at the side seam or a flattened rim. They weaken the rim, make lids fit poorly or leak, and can feel rough on the lips. Rim profile and diameter are checked at first-article inspection and during production.

Defects: films, plastic bags and pouches

Defect names for blown and cast films, printed bags and laminated pouches. Production steps are described in how plastic bags and film are made and how pouches and laminates are made.

Blocking (DE Blocken)

Blocking is unwanted adhesion between layers of film on a roll or between stacked bags, so that they are hard to separate or open. It comes from very smooth surfaces, heat and pressure in storage, too little antiblock additive, over-treatment or residual solvent. It is checked by opening bags or measuring the force to separate film layers, and it is a major defect where bags are opened by hand at speed.

Curl (film and laminate curl)

Curl is the tendency of a film, laminate, lid or bag to roll up instead of lying flat, caused by stresses built in during extrusion, orientation or lamination or by layers that react differently to heat and humidity. Curled film feeds poorly on packing machines, and curled pouches and lids are hard to fill and seal. It is assessed by measuring the lift or radius of a cut sample.

Gels and fish-eyes (DE Stippen)

Gels, or fish-eyes, are small clear or opaque lumps in plastic film formed by unmelted, cross-linked or contaminated polymer, often surrounded by a thinned zone that looks like an eye. They spoil print, can become pinholes or weak points under stress and are more frequent in films with recycled content. Gel counts per area are measured by optical scanners on the extrusion line or by visual inspection against a limit sample.

Pinholes (film)

Pinholes are tiny holes through a film, foil or laminate, caused by gels or contaminants that break when the film is stretched, by flex cracking, by abrasion or by sharp products. In barrier packaging a single pinhole can ruin shelf life, so pinholes are found with dye penetration, light tables or electrical detection. Thin foils and laminates that are flexed repeatedly are most prone.

Seal failure (weak seal; channel leak; burnt seal)

Seal failure covers heat seals that do not hold: weak seals peel open under load, channel leaks are narrow unsealed paths through wrinkles or trapped product, and burnt or over-sealed seals turn brittle and crack beside the seal line. Causes include temperature, pressure or dwell time outside the seal window, product contamination in the seal area and wrinkles. Seal failures are found with seal strength, burst and leak tests and are normally major or critical defects.

Tunnelling (laminate tunnelling)

Tunnelling is a laminate defect in which one layer lifts away from another in long, narrow raised channels, usually running in machine direction. It results from weak bonding combined with differences in tension or shrinkage between the layers during lamination, curing or later heating. Tunnels spoil appearance and can lead to seal failures and pinholes.

Putting test terms into a specification

A quality requirement is only as useful as its wording. For each property that matters to the pack, a specification should name the method and edition, the conditioning climate, the unit, whether the value is a minimum, maximum or target with tolerance, and how many specimens are averaged. For inspection, it should state the lot definition, inspection level and AQL per defect class, with a defect list and limit samples. Documents follow from that: a CoA per lot for the measured properties, a Declaration of Compliance for food contact and a retained-sample and lot-coding rule.

• Material tests: grammage, caliper and the strength property that matches the failure risk (tensile for handles, ECT for stacking, burst for puncture, seal strength for pouches).
• Barrier tests: KIT, Cobb, OTR or WVTR with test conditions stated.
• Functional tests on the finished item: handle load, leak, hot-fill, lid fit, drop or ISTA procedure.
• Print: colour references with ΔE formula and tolerance, registration tolerance, rub or tape test where handling is severe.
• Inspection: AQL, inspection level, defect classes, golden and limit samples.
• Documents: CoA, DoC, test reports and their renewal frequency.

The packaging RFQ guide shows where these lines sit in a quotation request, and packaging sampling and quality control explains how samples and inspections are scheduled. 9 Packaging is an Istanbul-based manufacturer and exporter of printed packaging for business customers, with experience supplying fast-food and chain-style foodservice operations; the tests and tolerances that apply to a particular order are confirmed at quotation and technical review. To have an existing specification or test requirement reviewed, send it through our contact page.