Search

Aluminium knowledge from A–Z

Technical terms relating to aluminium and aluminium processing, explained simply

In our aluminium glossary, you will find clear explanations of key technical terms relating to aluminium processing and production. Whether you are interested in profiles, alloys, surface treatments or manufacturing technologies – here you can find out what terms such as ‘anodising’, ‘to-size cutting’, ‘laminating’ or ‘embossing’ actually mean.

Our aim: Making technical knowledge clear and accessible – so that you, as a customer, architect, designer or buyer, can better understand how we work and the possibilities that aluminium offers.

A

Aluminium alloys are produced by deliberately combining pure aluminium with metals such as magnesium, copper, or manganese. The aim is to improve specific properties such as strength, formability, or corrosion resistance. There are both heat-treatable and non-heat-treatable alloys – depending on the application. Korff primarily processes soft aluminium alloys, which are characterized by good ductility and consistent material quality. These alloys are used, among other things, in technical foils, packaging materials, or laminated building systems. Even for demanding applications such as cable shielding or embossed decorative foils, the appropriate alloy ensures optimal performance and processability. All alloys used by Korff are recyclable and thus contribute to sustainable resource utilization.
Aluminium foil is an extremely thin metal sheet, usually less than 0.030 mm thick, which despite its low thickness offers a complete barrier against light, oxygen, moisture, and germs. This makes it ideal for use in packaging – especially for sensitive products like chocolate, coffee, or pharmaceutical applications. In construction, it serves as a vapor barrier or heat-reflective layer in insulation materials. Korff processes and supplies aluminium foil in various thicknesses, widths, and surface finishes, tailored to technical, food-related, or building physics requirements. Thanks to its in-house processing (lamination, coating, cutting), foil solutions can be flexibly adapted to customer needs. Aluminium foil also scores points with its high recycling potential – an ecological advantage that Korff actively promotes.
Annealing is a heat treatment that transforms the internal structure of cold-rolled aluminium foil. This process softens the material, improving its flexibility and elongation properties. At Korff, soft-annealed foil is preferred for applications requiring deep drawing, embossing or laminating, and also removes residual rolling oil from the surface.
Anodizing, also known as the Eloxal process, is an electrochemical surface treatment for aluminium, where a hard, protective oxide layer (Al₂O₃) is formed on the metal by anodic oxidation. This protective layer increases corrosion resistance and can also serve as a base for decorative coloring, as it is porous enough to absorb dyes that are then sealed. The anodizing process is mainly applied to solid aluminium components (e.g., profiles, sheets, or housings) to make their surfaces more durable and visually appealing. Aluminium foil, on the other hand, is only anodized in exceptional cases, as foils are usually refined by coating, laminating, or other methods. Korff in Switzerland, as a foil specialist, focuses on such alternative finishing processes, as anodizing is generally not required for the aluminium foils offered by Korff.

B

Barrier properties describe a material’s ability to prevent the passage of substances such as gases, moisture, or light. In this respect, aluminium foil offers exceptionally high barrier performance: from a thickness of about 0.01mm (10µm), it is virtually impermeable to water vapor, gases, and light. As a result, aluminium packaging reliably protects sensitive contents – food, beverages, or pharmaceuticals – from spoilage and quality degradation, significantly extending shelf life. In construction, aluminium-laminated sheets are used as vapor barriers because the metal foil does not allow any air or moisture to pass through. Korff in Switzerland utilizes the excellent barrier properties of aluminium in its foil products to ensure maximum protection in both packaging technology and technical insulation solutions.
Bauxite is the most important ore for aluminium production. It forms through the weathering of aluminium-bearing rocks in tropical climates and typically consists of about 50–60% aluminium oxide (Al₂O₃), along with iron oxides and silicates. Bauxite is mostly mined in open-pit operations. Aluminium oxide (also known as alumina) is first extracted from the raw ore and then reduced to metallic aluminium via the Hall-Héroult electrolysis process. Korff’s aluminium foil products in Switzerland are also made from aluminium originally derived from bauxite.

C

Aluminium foil is used in electrical engineering to shield cables from electromagnetic interference. In coaxial and data cables, an ultrathin aluminium layer—sometimes combined with a copper braid—is wrapped around the conductors. This foil blocks high-frequency interference and prevents signal leakage. Thanks to its good conductivity and flexibility, Korff supplies aluminium foil as a cost-effective alternative to pure copper, ensuring uniform coverage and high shielding performance (low impedance).
Capacitor foils are ultra-thin aluminium films (5–15 µm), made from high-purity aluminium and used in electrolytic capacitors. Two such foil layers (anode and cathode) are rolled together with a dielectric in between (e.g., paper or plastic). An oxide layer (Al₂O₃) grows on the anode foil during anodization to act as the dielectric. The surface quality and purity of the foil are crucial for capacitor capacity and reliability. Korff supplies precision aluminium foil that meets these demanding specifications.

The CO₂ footprint of a product (or company) refers to the total amount of greenhouse gas emissions, particularly carbon dioxide, caused directly and indirectly over its entire life cycle. For aluminium foil, the majority of these emissions arise from the primary production of the metal. Producing new aluminium from bauxite via electrolysis requires enormous amounts of energy and therefore causes high CO₂ emissions. In contrast, producing aluminium from recycled material requires only about 5% of the energy, reducing CO₂ output to a fraction. Manufacturers like Korff in Switzerland strive to reduce the CO₂ footprint of their aluminium products – for example, through increased use of recycled aluminium, energy-efficient production methods, and the use of green electricity. A minimal CO₂ footprint is particularly important for customers seeking sustainable and climate-friendly packaging solutions.

Korff AG enhances aluminium foil through specialized coatings to meet visual and functional requirements. Foils can be coated on one or both sides to protect print designs or to modify appearance (e.g., glossy, matte, colored). Protective, decorative, or functional coatings (such as heat-resistant lacquers) increase the foil’s durability. Korff ensures proper surface preparation (cleaning and degreasing) to guarantee strong adhesion of the coatings.
Korff’s aluminium foils feature a high level of corrosion resistance thanks to the natural oxide layer that forms upon exposure to air. Unlike iron, aluminium does not rust because this oxide barrier protects the metal from moisture and aggressive substances. This inherent resistance enhances the durability of Korff’s foils—even in challenging environments.

D

Degreasing refers to the removal of oil and grease residues from material surfaces – particularly metal surfaces. In aluminum processing – such as foil production – degreasing is a crucial step to remove rolling oil residues after cold rolling and to create a clean surface for subsequent processes (coating, lamination, food contact). Degreasing can be thermal (e.g. during soft annealing, where most oil evaporates) or chemical/plasma-based to ensure a nearly oil-free surface. Korff AG places high importance on thoroughly degreased aluminum foils to ensure excellent adhesion properties and consistent product quality.
Die-cutting allows precise shapes or cut-outs to be made in aluminum foil. Korff uses this method to produce custom pieces for packaging or industrial use, with consistent accuracy for automated processes.
Duplex foils consist of two layers, usually aluminium combined with paper, PE, or fleece. They combine the barrier properties of aluminium with the stability or flexibility of a second material. Korff offers such composite foils for packaging, construction, and insulation applications – robust, versatile, and tailored to the specific use case.

E

Aluminum conducts electricity very well while remaining lightweight. For this reason, it is often used in cables and as a shielding material. Korff supplies specialized conductive aluminum foils that serve as shielding materials against electromagnetic interference – for example, in construction applications or technical installations.

Die Elektrolyse ist das zentrale Verfahren zur Gewinnung von metallischem Aluminium aus Aluminiumoxid (Al₂O₃). Das heute weltweit eingesetzte Hall-Héroult-Verfahren, entwickelt Ende des 19. Jahrhunderts, bildet die Grundlage der modernen Aluminiumproduktion.

Dabei wird das zuvor aus Bauxit gewonnene Aluminiumoxid in einer Schmelze aus Kryolith (Na₃AlF₆) bei etwa 950 °C gelöst. Durch das Anlegen eines starken elektrischen Stroms wird das Aluminiumoxid in seine Bestandteile zerlegt: Sauerstoff verbindet sich mit der Kohlenstoffanode zu CO₂, während sich flüssiges Aluminium an der Kathode absetzt und anschließend abgegossen wird.

Dieser Prozess ist energieintensiv und verursacht den größten Teil der CO₂-Emissionen in der Aluminiumherstellung. Daher setzt die Korff AG auf recyceltes Aluminium und energieeffiziente Produktionsverfahren, um die ökologische Bilanz ihrer Aluminiumfolien deutlich zu verbessern.

Durch den gezielten Einsatz von Sekundäraluminium können bis zu 95 % Energie gegenüber der Primärproduktion eingespart werden – ein entscheidender Beitrag zu Nachhaltigkeit, Ressourcenschonung und Klimaschutz.

Tensile elongation indicates how far aluminium foil can plastically stretch under tensile load before it tears. Soft-annealed foils from Korff exhibit particularly high ductility and can therefore be easily formed – for example, during deep drawing or for complex packaging tasks.

Embossing is a mechanical process that creates a textured pattern on the surface of aluminium foil. This can be used for decorative purposes or to enhance functionality—such as improving grip, rigidity, or optical effects. Korff offers embossed foils for applications where appearance, handling, or further processing properties benefit from structured surfaces.
A measure of environmental impact during the production, use, and recycling of a product. Aluminum has a favorable footprint, as it is 100% recyclable and requires only about 5% of the original energy in recycling. Korff leverages this by producing recyclable foils and reintroducing production scrap. Through sustainable practices, Korff helps reduce the carbon footprint.

F

A foil roll (aluminum roll) is a continuous strip of aluminum foil wound onto a core, providing a long, uninterrupted foil web. This format allows easy transport, storage, and further processing of even extremely thin aluminum foils without tearing or creasing. Korff AG offers foil rolls in various dimensions – typically up to 1000 mm in width and foil thicknesses ranging from approx. 0.008 mm to 0.300 mm – tailored to numerous industrial and technical applications. Due to the rolling process, aluminum foil up to 0.040 mm usually has two distinct surfaces: one shiny and one matte, allowing targeted use depending on needs such as reflectivity or adhesion.
Aluminium foil is considered food-grade when used properly and is safe for direct contact with most foods. In neutral environments, it does not transfer substances and protects contents from light, odors, and external influences. However, acidic or salty foods should be avoided, as they can induce aluminium ion migration. Under correct guidelines, Korff’s food-grade foils are reliably safe for consumer use.
A mechanical process in which aluminum sheets or foils are bent, stamped, or deep drawn into shape. Korff aluminum foils are highly ductile and easy to form – ideal for pre-shaped packaging or functional components.

G

Gloss level measures how much light a surface reflects – in other words, how shiny or matte it appears. It is typically measured in gloss units (GU) using a gloss meter. Thin aluminium foils (up to 0.040 mm) have a glossy side and a matte side due to the rolling process. Korff AG considers the desired gloss level when selecting or processing foils, depending on optical or technical requirements such as reflectivity or print adhesion.

H

Household aluminium foil, typically 10–20 μm thick, is used for food preservation, covering dishes or oven grilling. One side is shiny, the other matte, and it comes in rolls. Korff supplies household foil in standard roll formats and ensures its high quality and suitability for food use – light- and odor-proof, heat-resistant, but not microwave safe.

I

Thin aluminium foil used in building insulation as a heat-reflective and moisture-barrier layer. Korff produces custom insulation foils that reflect radiant heat and improve energy efficiency in roofs, walls, and floors. The foils are flame-retardant and maintain performance thanks to Korff’s high-grade aluminium alloys.

J

A jumbo roll is an oversized roll of aluminium foil used in high-volume industrial processes. Korff provides jumbo rolls with optimized winding and core stability to support long, uninterrupted production runs in the packaging and converting sectors.
Just-in-Time is a logistics strategy where materials are delivered precisely when needed for production. Korff follows the JIT principle to supply aluminium foils efficiently – reducing storage costs and waste for customers through accurate planning and reliable delivery performance.

K

L

Laminated foils consist of aluminum and at least one other material (e.g. paper or plastic), combining the benefits of each in a single product. At Korff, we design composite foils to meet specific demands for barrier protection, tear resistance, and visual appearance – tailored to the application.

In lamination, aluminium foil is bonded to additional layers (e.g., paper, plastics, non-wovens) to form a composite. These laminated foils combine the foil’s barrier properties with the mechanical stability of a backing. Korff’s laminated foils offer increased tear resistance and rigidity compared to plain foil, improving printability and processing. These composites are widely used in packaging when both barrier and structural qualities are required.

The London Metal Exchange (LME) is the world’s leading industrial metals market, where aluminium is actively traded. The LME spot price serves as the reference for aluminium products—including Korff’s aluminium foils. Buyers and manufacturers often negotiate prices based on the current LME value plus premiums for rolling and finishing. Fluctuations in the LME directly influence Korff’s foil procurement costs.

M

Metallised films are plastic films (e.g. PET) that are coated with an ultra-thin layer of aluminium in a high-vacuum process. They offer a decorative metallic shine and moderate aroma barrier properties, making them ideal for less demanding applications such as snack packaging or gift wrap. Unlike solid aluminium foil, metallised films consist almost entirely of plastic and contain only trace amounts of aluminium. At Korff, we use metallised films selectively where appearance is a priority and full barrier protection against light or moisture is not required.

N

O

An oxide layer is a natural protective film of aluminium oxide that forms immediately when aluminium is exposed to air. Korff aluminium foils develop this ultra-thin layer automatically, which protects the material from corrosion. This oxide skin significantly improves resistance to environmental and chemical influences and increases the service life of our foil products.

P

Perforated foils feature strategically placed micro or macro holes. Depending on the size and pattern, perforation allows improved ventilation, easier tearing, or targeted steam release in technical applications. Korff uses perforated foils in fresh food packaging, steam-cooking pouches, or industrial products requiring controlled air exchange—balancing protection with breathability.
Pinholes are microscopic perforations that can occur in very thin foil during production. They are nearly unavoidable in aluminium foil below 6µm and can compromise barrier performance by allowing air or moisture to pass through. For sensitive applications – such as food or pharmaceutical packaging – Korff relies on thicker aluminium foil or multilayer laminate constructions to ensure maximum impermeability.
Primary aluminium is extracted directly from bauxite ore and is characterised by high purity. Its production is energy-intensive and takes place in large smelters around the world. At Korff, we only use primary aluminium when exceptionally high material quality is required. Wherever possible, we prioritise the use of recycled aluminium to reduce environmental impact and optimise cost-efficiency.
Printing aluminium foil using flexographic printing refers to a process in which colors, text, or patterns are applied to foil surfaces. Flexographic printing is a high-speed rotary printing process based on the relief printing principle: flexible photopolymer printing plates are mounted on cylinder sleeves and transfer the ink from their raised areas directly onto the moving aluminium foil. This technique is particularly suitable for packaging foils, as it enables precise print images at high production speeds even on difficult substrates such as thin metal foil. Korff in Switzerland uses flexographic printing to offer customers printed aluminium foils with customized designs and markings.
This value indicates how resistant a foil is to sharp-edged loads. Aluminium foil naturally has good puncture resistance, which can be further enhanced through targeted laminations – such as fabric reinforcements. Korff offers reinforced aluminium foils that provide reliable protection, particularly in construction or packaging applications with high mechanical demands.
Depending on the application, aluminum foil may require high purity or specific alloy content. Korff offers both – from ultra-pure foils for sensitive electronics to alloyed foils optimized for strength, flexibility, or barrier function.

Q

Korff ensures consistent product quality through rigorous checks, including thickness measurement, surface inspections, and standardized testing. Certified quality management (e.g. ISO 9001) guarantees that Korff aluminum foils meet all technical requirements and customer expectations.

R

Aluminum can be recycled endlessly without loss of quality. Recycling requires only ~5% of the energy used in primary production, saving resources and cutting CO₂ emissions. Korff actively integrates recycled aluminum into its production to combine ecological responsibility with technical excellence.
Aluminum foil reflects up to 96% of radiant energy, making it ideal for heat and light management. Korff uses this feature in insulation products and packaging solutions requiring thermal shielding or reflective performance.

A primer enhances adhesion of adhesives, inks, or lacquers to the back of aluminum foil. Korff applies tailored reverse coatings to prepare foil for specific downstream steps such as lamination or printing.

Rolling is the core process for producing aluminum foil. The material is reduced to the desired thickness in multiple passes. Korff uses only quality-certified rolled products and ensures tight tolerances, clean surfaces, and excellent downstream workability – whether for packaging, technical, or construction applications.

S

A sealing layer is a functional coating on aluminum foil that enables thermal bonding to containers or lids. Korff applies such sealable layers to lidstock and other food contact foils, combining tight seals with controlled peelability – crucial for dairy, snack, and medical packaging.
Secondary aluminum is derived from recycled material but offers nearly identical properties to primary aluminum. Korff uses secondary aluminum wherever possible to reduce environmental impact without compromising on quality or performance.
A sheet format is a material piece – for example, aluminum foil – cut to specific dimensions. Instead of manually cutting a supplied roll to the desired size, the user receives pre-cut foil pieces. This saves time and ensures dimensional accuracy. Korff AG offers such aluminum sheet formats in both standard sizes and custom cuts tailored to customer specifications. This is particularly useful for technicians and processors, as it eliminates the need for on-site cutting and reduces material waste.
Korff AG uses slitting to cut wide aluminium foil rolls into precise narrower widths. In slitting machines, the running foil web is cleanly segmented by rotating blades. This process produces core-wound rolls with exact widths, ideal for downstream processing on converters and packaging machines. Smooth, burr-free edges ensure trouble-free production.
Surface finishing refers to functional or decorative treatments applied to aluminium foil. At Korff, we use coatings, lacquering, or lamination to enhance resistance to moisture or to make the foil suitable for printing. These processes improve the durability and appearance of our foil products across various applications.

T

Tensile strength is a key property of aluminum foil – it indicates the maximum load the material can withstand before breaking. At Korff, this value is a critical factor in selecting the right alloy and foil thickness for each application. Whether for packaging, deep drawing, or technical laminates, our products are matched to the specific strength requirements of industrial use.
Korff processes aluminum foil with high thermal conductivity (approx. 235 W/m·K), allowing fast heat distribution. This is critical for applications requiring efficient heat dissipation or even heat distribution – such as warm food packaging or technical insulation films. Korff’s foils adapt quickly to temperature changes and help transfer or store heat effectively.
Korff uses aluminum foil for applications where thermal radiation reflection is key – such as in insulation materials or technical barrier systems. Thanks to its high reflectivity (up to 96%), it effectively reduces heat loss. Typical examples include multilayer reflective foils, air bubble foils with aluminum coating, and special laminated foils supplied by Korff in Switzerland. Additionally, aluminum foil acts as a fire protection layer since it is non-combustible.
Permissible deviation from specified dimensions or properties. In Korff aluminum foils, tolerance refers for example to allowed variations in thickness or width. Tight tolerances are essential for further processing, ensuring the foil runs smoothly on unwinders and packaging machines. Korff produces foils with precise tolerances to guarantee consistent quality and trouble-free processing at the customer’s site.

U

V

Aluminium foils are used in construction as vapor barriers to prevent the penetration of water vapor into insulation materials. Their high density reliably protects against moisture damage and mold. Korff offers laminated aluminium foils with fleece or paper layers that are easy to process and particularly tear-resistant – ideal for roof, wall, and floor constructions.

W

X

This non-destructive analytical method determines the chemical composition of materials by bombarding them with X-rays and measuring the fluorescent radiation emitted. In aluminum foil, XRF is used to check alloy composition, purity, or coating thickness. Manufacturers use this to verify compliance with specifications (e.g. purity level, alloying elements) and meet recycling and quality standards. XRF analysis supports quality assurance and sustainable processing.

Y

In production, yield refers to the ratio of usable finished product to the material input. In aluminum foil manufacturing, it measures efficiency – how much of the input aluminum becomes usable foil. A high yield means less waste and lower cost. Korff optimizes its processes to maximize yield, reducing scrap and recycling needs and improving material efficiency in packaging solutions.
Yield strength defines the point at which aluminum foil deforms permanently under stress. Korff ensures its foils meet the required strength or formability for each application – from deep-drawing to technical laminates.

Z