Metal Packaging Terminology

Index

1. Metal Materials & Coatings
2. Metal Sheet Processing
3. Manufacturing Process & Equipment
4. Geometry & Structural Features
5. Aerosol Can Terminology
6. Aluminum Bottle Terminology
7. Aluminum Can Terminology
8. Chemical Can Terminology
9. Food Can Terminology
10. Metal Closure Terminology
11. Filling, Pressure & Performance
12. Surface Finishing & Decoration
13. Quality & Testing
14. Industry Reference

Aluminum (Monobloc): A seamless one-piece aluminum container body, usually formed by impact extrusion. "Monobloc" simply means the body is made from one piece rather than separate pieces joined together. This design is common for aluminum aerosol cans and aluminum bottles because it reduces side seam concerns and provides a clean, premium appearance.

Electrolytic Tin Coating (ETP): A controlled tin layer applied to steel by electroplating. This process allows manufacturers to control how much tin is deposited on the surface, which affects corrosion resistance, appearance, and cost. Different tin coating weights may be selected depending on the product filled inside and the performance needed.

External Coating: A coating applied to the outside of the container for protection, appearance, or both. It can help resist scratches, moisture, and handling damage, while also serving as the base for printing or final finish appearance.

Internal Coating (Lacquer): A protective organic coating applied to the inside of the metal container. Its main purpose is to keep the product from directly contacting the metal surface, which can otherwise cause corrosion, staining, flavor change, or package failure. Different products require different lacquer systems depending on their chemistry.

Tinplate: Steel sheet coated with a very thin layer of tin. The steel provides strength, while the tin helps protect the surface from rust and improves resistance to certain products. Tinplate has long been used in food cans, chemical cans, and closures because it combines good formability with reasonable corrosion protection.

TFS (Tin-Free Steel): Steel sheet coated with chromium or chromium oxide instead of tin. It is often used when strong paint or lacquer adhesion is needed, but it does not behave the same way as tinplate in joining and corrosion performance. Because it has no tin layer, it is generally not suitable for traditional soldering and relies more on welding, cementing, or coating systems.

Coil: Large roll of metal sheet used as the starting material for can, bottle, or closure production. Instead of making packaging from small individual sheets one by one, manufacturers typically process metal from coils for efficiency and consistency.

Sheet Cutting (Slitting): The process of cutting wide metal coils into narrower strips or individual sheets before forming. Different widths may be needed depending on the can size, closure size, or production equipment. This is one of the early preparation steps before the metal is shaped into packaging components.

Temper: The hardness and strength condition of the metal. A higher temper generally means the material is stronger but may be less easy to form, while a lower temper is easier to shape but may be less rigid. Choosing the right temper is important because packaging must be formable during production but still strong enough in use.

Thickness: The thickness of the metal sheet. Thicker metal usually improves strength and dent resistance, but it also increases weight and cost. Packaging design often balances thickness, performance, and lightweighting goals.

Lubrication: Oil or other lubricating material applied during forming to reduce friction between the metal and the tooling. Without lubrication, the metal can scratch, tear, or wear the tools more quickly during shaping operations.

Three-Piece Can: A metal can made from three main parts: a body, a top end, and a bottom end. The body is usually rolled from flat sheet into a cylinder and joined at the side seam, then the top and bottom are attached separately. This style is common for many food cans and chemical cans.

Two-Piece Can: A can made from a body and base formed together as one piece, plus a separate top end. Because the sidewall and bottom are integrated, there is no side seam along the body. This structure is common where improved appearance, pressure performance, or higher-speed production is desired.

Impact Extrusion: A process in which a metal slug, often aluminum, is struck with very high force so it flows upward around a punch and forms a seamless container body. This is how many aluminum aerosol cans and aluminum bottles are made. It is useful because it creates a strong, one-piece body with no welded side seam.

D&I or DWI: Draw & Iron (also known as Drawn and Wall Ironed) is a process used to make aluminum beverage cans, where a flat sheet of metal is first "drawn" into a shallow cup and then stretched taller and thinner through multiple forming rings. As the metal is pulled upward, the walls become thinner while the base remains thicker for strength, creating a lightweight but durable can body.

Unlike impact extrusion, which starts from a solid metal slug and forms the container in one main step by forcing material to flow upward, D&I starts from a flat sheet and gradually shapes it through several steps. This allows D&I cans to be produced at very high speed with thinner walls, making them more material-efficient and suitable for high-volume applications like beverages.

Side Seam Welding: The process of joining the two vertical edges of a rolled can body to form a cylinder. This is a critical step for three-piece cans because the seam must be strong and leak-resistant. After welding, the seam area is often coated internally to restore corrosion protection.

Necking: A forming process that gradually reduces the diameter at the top of an extruded can or bottle. This is often done to fit a smaller closure, reduce material usage, improve pouring or handling, or create a more attractive package shape. Because the metal is being re-formed, the process must be carefully controlled to avoid wrinkles or cracks.

Flanging: The process of turning the top or bottom edge of a can body outward to create a flange. This flange is needed so the end can be attached by seaming. In simple terms, it prepares the edge of the body for final assembly.

Seaming: A mechanical joining process that interlocks the curled edge of the can end with the flanged edge of the can body. The result is called a seam, and it creates the final connection between components. Proper seaming is critical because poor seam formation can cause leaks, contamination, or loss of pressure.

Trimming: A cutting step used to remove excess metal and create the final container height or edge condition. It helps ensure consistency from one container to the next and prepares the container for downstream operations such as necking or seaming.

Body: The main sidewall section of the container that holds most of the product volume. It is the largest structural part of the package and is often the main area for printing and decoration.

Shoulder: The curved or angled area between the main body and the neck. It is common in aerosol cans and aluminum bottles. This transition area affects appearance, strength, and how the package fits filling or capping equipment.

Neck: The upper section of the container between the shoulder and the opening. It is usually narrower than the body and is designed to work with the closure or dispensing system.

Finish: The part of the opening area designed to interface with a closure, valve, or cap. It may include threads, a sealing surface, or a crimp area. In packaging terminology, the "finish" is the functional top portion that determines how the package closes.

Base (Bottom Dome): The bottom section of the container. In pressure containers, the base is often domed rather than flat because a curved shape handles internal pressure more effectively. In non-pressure packages, the base may be designed more for standing stability.

Chime: The reinforced outer edge at the top or bottom of a can end. It provides strength, helps protect the seam area, and improves handling and stacking performance. On finished cans, it is often the edge that first contacts surfaces during movement or storage.

Bead: A circular groove or indentation formed around the body of a can. It improves rigidity and helps the container resist buckling, denting, or pressure-related deformation. In simple terms, it acts like a strengthening feature built into the wall.

Paneling: Visible inward deformation of the container wall, usually caused by pressure imbalance. For example, if internal vacuum becomes too strong or the container is not strong enough, the sidewall may pull inward. Paneling is generally considered a defect because it affects appearance and may indicate performance issues.

Aerosol Can: A pressurized container designed to dispense product in spray, foam, gel, or mist form. It uses a combination of product, propellant, valve, and actuator to release the contents in a controlled way.

Valve: The mechanical part attached to the top of the aerosol can that controls when and how the product is released. When the user presses the actuator, the valve opens and allows product to flow out. Valve design affects spray pattern, dosage, and compatibility with the formula.

Actuator: The button or spray head pressed by the user. It sits on top of the valve stem and directs the product out of the can. Different actuator designs can create different spray shapes, flow rates, or user experiences.

Dip Tube: A plastic tube connected to the valve and extending down inside the can. It carries the liquid product from the bottom of the can up to the valve during use. Without it, much of the product would remain inside and could not be dispensed properly.

Propellant: The gas system that pushes the product out of the container. It may be a liquefied gas such as LPG or a compressed gas depending on the application. The propellant not only drives dispensing but also affects internal pressure and package performance.

Mounting Cup: The metal cup component that holds the valve assembly and connects it to the can opening. It is the part that gets crimped onto the top of the can. It must fit properly and seal well to prevent leakage.

Crimping: The process of mechanically fastening the mounting cup and valve assembly onto the aerosol can opening. The metal edge is compressed into place to create a secure seal. Correct crimp dimensions are very important because poor crimping can lead to leaks or pressure loss.

Burst Pressure: The internal pressure level at which the can fails or ruptures. This is a safety-related performance value used during qualification and testing. The normal working pressure of the package must remain well below this failure point.

Working Pressure: The pressure the aerosol container is expected to withstand during normal storage and use. This is not the failure point, but the normal operating range the package must safely handle.

Aluminum Bottle: A lightweight metal bottle, usually seamless, commonly used for personal care, beverages, household products, and some chemicals. Compared with plastic, aluminum bottles often offer a more premium appearance and strong barrier performance. Compared with glass, they are lighter and less fragile. Pure aluminum bottles (heavier, more premium) are made from impact extrusion, while aluminum alloy bottles (lighter, lower-cost) are made from D&I.

Threaded Neck (RFS / ROPP Compatible): The upper neck design of the bottle prepared to work with a screw cap or roll-on closure. This area is critical because it determines closure fit, sealing performance, and user opening experience.

RFS (Roll-Formed Thread): A pre-formed thread built into the aluminum bottle neck before filling and capping. This allows the bottle to use standard screw-type closures. It is useful when a conventional threaded cap is preferred.

ROPP Finish (Roll-On Pilfer Proof): A smooth aluminum bottle neck designed for use with an aluminum closure that is formed onto the bottle during application. Instead of starting with finished threads, the capping process creates the thread shape directly on the closure. This style is often used for spirits, beverages, and premium products where tamper evidence is important.

Shaping (Reforming): A secondary forming process used after the initial bottle body is made. It changes the simple cylindrical shape into a more distinctive package design. This is how aluminum bottles can achieve contours or styling features while still starting from a seamless body.

Internal Coating (Aluminum Bottles): A protective lacquer applied inside the container to keep the product from reacting with the aluminum. This is especially important for beverages, acidic products, and aggressive formulations that could otherwise corrode the metal or affect taste and stability.

Base Design (Flat / Domed): The structure of the bottom of the bottle. A flat base is typically used where stable standing is the main priority, while a domed base may be chosen when improved pressure resistance is needed. The base design depends on the application and filling conditions.

Aluminum Aerosol Can: A seamless, one-piece pressurized container formed by impact extrusion, designed to safely contain product and propellant for spray applications such as personal care and household products.

Aluminum Beverage Can (D&I Can): A high-volume two-piece container made using the draw and iron (D&I) process, where the body and base are formed from a single piece of aluminum, eliminating side seams. Commonly used for carbonated beverages.

Easy-Open End (EOE): The top lid of the can with an integrated score line and pull tab, allowing consumers to open the can without tools. Commonly used for 2-piece beverage cans.

SOT (Stay-On Tab): A type of easy-open can end where the tab remains attached to the lid after opening. When the tab is lifted, it pushes the scored panel inward to create the opening, but the tab does not fully detach. This design improves safety by reducing loose metal pieces and is widely used in aluminum beverage cans.

FAE (Full Aperture End): A type of easy-open can end designed to create a large, fully open access when opened, typically by pulling back a scored section of the lid. Unlike standard SOT designs, FAE provides a wider opening, making it easier to pour, consume directly, or access the contents. It is commonly used for specialty beverage cans or food applications where full access is preferred.

F-Style Can: A rectangular metal can, usually with a handle, commonly used for solvents, oils, cleaners, and industrial chemicals. Its shape helps with pouring, stacking, and efficient shipping.

Tight Head Can: A can with a permanently fixed top and one or more small threaded openings (bungs) for filling and dispensing. It is typically cylindrical in shape, similar to a drum or pail, with a flat or slightly domed top and bottom. The small openings are usually located on the top panel and fitted with screw caps or plugs. Because the full top cannot be removed, this design provides better sealing performance and is commonly used for liquids requiring strong containment and leak resistance.

Open Head Can: A can with a fully removable top that is secured using a clamp ring or lever-lock mechanism. It is generally cylindrical with a straight body and a wide opening equal to the full diameter of the can, allowing complete access to the interior. This design makes it easier to fill, empty, or handle products that are viscous, solid, or packaged in liners, and is commonly used for industrial chemicals, powders, or bulk materials.

UN Certified Packaging: Packaging tested and approved to meet United Nations transport requirements for hazardous materials. This does not just mean the container looks strong; it means the package design has passed specific regulatory performance tests for the assigned use condition.

Closure Plug (Bung): A threaded plug fitted into the opening of a can or drum for filling, dispensing, or resealing. It is often used on chemical packaging where controlled pouring and secure closure are important.

Handle (Bail Handle): A carrying handle, usually made of metal or plastic, attached to the container. It improves usability, especially for heavier packs such as solvents or industrial liquids.

Stacking Strength: The ability of the package to support weight from other containers placed on top during warehousing or transport. Good stacking strength is important because many industrial packages are stored in stacked pallet loads.

Commercial Sterility: A condition achieved after retort processing where all harmful microorganisms are destroyed to a safe level. This does not mean completely sterile, but safe for long-term storage under normal conditions.

Food Can: A metal container specifically designed for food products, typically made from tinplate or aluminum with food-grade internal coatings. These cans are used for both liquid and solid foods, including products like vegetables, meats, and powdered products such as milk powder or infant formula.

Micro-Leak (Loss of Hermeticity): A very small leak in the seam that may not be immediately visible but allows air or microorganisms to enter over time. This can lead to spoilage even if the can initially appears intact.

Peelable Foil Seal (Membrane Seal): An inner seal applied to powder cans or specialty food packaging, typically made of aluminum foil laminate. It provides an additional barrier against moisture and contamination and is removed by the consumer after first opening.

Powder Can (Milk Powder / Infant Formula Can): A specialized food can designed for dry products, often featuring a larger diameter and shorter height for stability and ease of scooping. These cans are typically paired with plastic overcaps, peelable membranes, or foil seals to maintain product freshness and prevent moisture ingress.

Retort Processing: A high-temperature sterilization process applied to sealed food cans to achieve commercial sterility and extend shelf life. The can must withstand both elevated temperature and internal pressure during this process without losing seal integrity.

Metal Cap (Closure): A metal component used to seal the opening of a bottle, jar, or can. The closure does more than simply cover the opening; it must also create the right seal, protect the product, and sometimes provide tamper evidence or dispensing function.

Continuous Thread (CT) Cap: A screw cap with a continuous spiral thread that matches the thread on the container finish. It is removed and reapplied by twisting. This is one of the most common closure styles for bottles and jars.

Lug Cap: A cap with interrupted thread segments rather than a full continuous spiral. It seals with only a partial turn, which makes it convenient in many food packaging applications. The matching container finish is also specially designed for this closure style.

Crown Cap: A metal cap, usually crimped onto a bottle finish, commonly used for beverages. It creates a secure seal and is often removed with a bottle opener unless it includes a twist-off design.

ROPP Closure: An aluminum cap that is applied onto a bottle neck and formed during capping to match the container finish. It is widely used where tamper evidence, premium appearance, or secure closure performance is needed.

Liner: The sealing material inside the closure that contacts the container finish. The liner is often what actually creates the seal, not the metal shell itself. Different liner materials are selected based on the product, sealing method, and performance needs. Common ones include PVC liner, TPE liner, and BPA-NI liner.

Torque: The turning force used to apply or remove a closure. Proper torque matters because too little torque may lead to leaks, while too much torque may damage the closure, liner, or user experience.

Headspace: The empty space between the top of the product and the closure or valve. This space is often necessary for thermal expansion, pressure control, sealing performance, or dispensing function.

Internal Pressure: The pressure inside the package generated by the product, propellant, gas, or temperature changes. Some packages are designed to contain pressure, while others are not. Understanding expected internal pressure is critical in metal packaging selection.

Vacuum: A condition where the pressure inside the package is lower than the pressure outside. This often happens after hot filling and cooling. Vacuum can help hold a closure in place, but excessive vacuum can also deform weak containers.

Leak Integrity: The ability of the finished package to prevent product, gas, or pressure from escaping. This is one of the most basic performance requirements of any sealed metal package.

Compatibility: The relationship between the product and the packaging system, including metal, coatings, closure, and seals. A package may look correct physically but still fail over time if the formula attacks the metal or coating. Compatibility is confirmed typically through stability testing, where the formula is filled into the packaging container and observed at 30, 60, and 90 days in various temperatures.

Lithography: A printing process applied to flat metal sheets before they are formed into cans or other components. It is essentially a form of offset printing adapted for metal, allowing large volumes of sheets to be decorated efficiently and consistently. Because the artwork is printed before forming, the design must account for how the metal will stretch or move during manufacturing. For a closer look at this method and its applications, explore Evergreen's litho printing page.

Offset Printing: A high-resolution printing method where ink is first transferred from a printing plate to a rubber blanket, and then from the blanket to the metal surface. This method provides sharp detail, good color consistency, and strong graphic quality. It is commonly used when appearance is important, especially for branded consumer packaging. For additional detail on this process and where it's typically used, explore Evergreen's offset printing page.

Embossing / Debossing: A forming process that creates raised or recessed features in the metal surface. Embossing produces a raised design, while debossing creates an indented one. These features can improve shelf appearance, add brand differentiation, or even increase grip or local rigidity. For more information on how this technique is used in metal packaging, explore Evergreen's emboss & deboss page.

Varnish / Overcoat: A protective top layer applied over printed or decorated surfaces. It helps protect inks from scratching, rubbing, moisture, or chemical exposure during production, transportation, and use. It can also change the final visual effect, such as gloss, matte, or specialty finishes.

Matte / Gloss Finish: Terms describing how reflective the final package surface appears. A gloss finish looks shiny and reflective, while a matte finish looks softer and less reflective. Beyond appearance, the finish choice can also affect how fingerprints, scratches, and handling marks show on the pack. For more on how these finishes are applied in packaging, you can explore Evergreen's matte finish page.

Seam Test (Double Seam Analysis): A destructive test used to evaluate the integrity of the double seam where the can body and end are joined. The seam is cut and examined under a microscope or seam measurement system to check critical parameters such as seam thickness, overlap, body hook, and end hook. Proper seam formation ensures hermetic sealing and prevents leakage, contamination, or pressure loss.

Enamel Rating: A test used to evaluate the integrity of the internal coating by checking how much bare metal may be exposed. One common method uses an electrical test to detect coating discontinuities. The better the coating coverage, the lower the risk of corrosion or product interaction.

Drop Test: A test in which the package is dropped from a defined height and orientation to simulate handling or shipping impacts. It helps evaluate whether the container can survive normal abuse without denting badly, leaking, or failing structurally.

Pressure Test: A test that applies internal pressure to the package to confirm it can safely withstand expected use conditions. It is especially important for aerosol cans and other pressure-containing packs. This test helps verify both safety margin and structural performance.

Leak Test: A test used to detect whether a sealed package allows product, gas, or pressure to escape. Different methods may be used, such as vacuum testing, pressure decay testing, or water bath observation. Leak testing is especially important for aerosols, chemicals, and any product where seal integrity matters.

Water Bath Test (Leak Test): A leak detection method commonly used for aerosol cans and pressurized containers. Filled cans are submerged in a water bath while under internal pressure, and operators visually inspect for escaping air bubbles, which indicate leakage points. This test is widely used on production lines because it is simple, effective, and allows quick identification of sealing defects such as poor crimping or seam issues.

Corrosion Resistance: The ability of the container and its coating system to resist attack from the product or surrounding environment. Poor corrosion resistance may lead to rust, staining, coating failure, leakage, or eventual structural weakening of the package.

Dent Resistance: The ability of the package to resist permanent deformation when impacted or compressed. Dent resistance depends on factors such as material thickness, temper, shape, beads, and overall structural design. Good dent resistance is especially important during shipping, retail handling, and consumer use.

CSPA Standard (Aerosol Can Standard): An industry standard originally developed by the Consumer Specialty Products Association for necked-in and straight-wall three-piece aerosol cans, defining key dimensions and specifications to ensure compatibility across components such as cans, valves, and filling equipment. The standard was revised and reapproved in 2009 by the CSPA Aerosol Products Division.

In 2018, CSPA was renamed the Household & Commercial Products Association (HCPA). The updated HCPA standard maintains the same dimensional and specification requirements with no changes from the previous version. As a result, existing CSPA standards remain fully applicable and continue to be widely used in the industry.

CMI (Can Manufacturers Institute): An industry organization representing metal packaging manufacturers and supporting standards, education, and advocacy related to can production and performance.

UN Regulations (United Nations Model Regulations): International guidelines developed by the United Nations for the transport of dangerous goods across all modes (road, sea, air, and rail). These regulations define classification systems, packaging performance standards (e.g., UN-certified packaging), labeling, and testing requirements. They serve as the global framework that many countries adopt or base their local regulations on.

DOT Regulations (U.S. Department of Transportation): U.S.-specific regulations governing the transportation of hazardous materials within the United States, primarily under 49 CFR. DOT regulations adopt the UN framework but include additional requirements for domestic transport, enforcement, labeling, documentation, and packaging approvals to ensure compliance within the U.S. transportation system.