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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 combinations of aluminium with other elements that are used to achieve specific material properties, such as increased strength, corrosion resistance or improved processing characteristics.

These alloys are used, among other things, in technical foils, packaging materials and laminated building systems. For demanding applications such as cable shielding or embossed decorative foils, the appropriate alloy ensures reliable performance and good processability. The aluminium alloys used by Korff AG can generally be returned to the aluminium recycling process.

Aluminium foil is an extremely thin metal sheet, usually less than 0.030 mm thick. Despite its low thickness, it provides a high barrier against light, oxygen and moisture. This makes it particularly suitable for packaging sensitive products such as chocolate, coffee or pharmaceutical products. In construction, aluminium foil is also used as a vapour barrier or heat-reflective layer in insulation systems.

Korff AG processes and supplies aluminium foil in various thicknesses, widths and surface finishes, tailored to technical, food-related or building physics requirements. Thanks to in-house processing such as lamination, coating and cutting, foil solutions can be flexibly adapted to customer requirements.

Aluminium foil can generally be recycled, provided that it is appropriately collected, sorted and suitable for the respective recycling process. In the case of coated, printed or laminated aluminium foils, recyclability depends on the specific product composition and the available recycling processes.

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 describes the amount of greenhouse gas emissions associated with a product, process or activity. In the case of aluminium, emissions can occur at different stages, including raw material extraction, aluminium production, processing and transport.

The CO₂ footprint of aluminium depends, among other factors, on the raw material used, the energy supply during aluminium production, the processing steps and the transport routes.

Recycled aluminium generally requires significantly less energy to produce than primary aluminium. For specific statements about the CO₂ footprint of products processed or supplied by Korff AG, however, product-specific data is required.

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.

Electrolysis is the central process used to produce metallic aluminium from aluminium oxide (Al₂O₃). The Hall-Héroult process, which is used worldwide today and was developed at the end of the 19th century, forms the basis of modern aluminium production.

In this electrolysis process, aluminium oxide previously obtained from bauxite is dissolved in molten cryolite (Na₃AlF₆) at approximately 950 °C. A strong electric current separates the aluminium oxide into its components. Oxygen reacts with the carbon anode to form CO₂, while liquid aluminium is deposited at the cathode and subsequently removed.

The production of primary aluminium by electrolysis is energy-intensive. Reprocessing aluminium generally requires significantly less energy. The actual energy requirement depends on the raw material and the recycling process used.

For Korff AG, the Hall-Héroult process and other upstream production processes are relevant as background knowledge for the aluminium materials and foils that are subsequently processed into customer-specific products.

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.

The environmental footprint considers the environmental impacts of a product across different stages of its life cycle, such as raw material extraction, production, transport, use and recovery.

The actual environmental footprint of an aluminium product depends, among other factors, on the raw material used, energy supply, product composition, transport routes and available recycling processes.

For products processed or supplied by Korff AG, a specific environmental footprint assessment therefore requires product-specific data and cannot be derived solely from the material aluminium itself.

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

Insulation foil made of aluminium is used in construction and technical applications as a heat-reflective or moisture-barrier layer.

Due to its high reflectivity, insulation foil made of aluminium can help reflect thermal radiation and reduce heat loss when used in suitable constructions.

Korff AG supplies insulation foils and composite solutions for insulation applications and adapts material structure and processing to the technical requirements of the respective application.

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 aluminium produced directly from aluminium oxide obtained from bauxite. Primary aluminium is characterised by a high degree of purity and is used for applications requiring precisely defined material properties.

The production of primary aluminium is energy-intensive. Where technical requirements permit, recycled aluminium can be an alternative to primary aluminium.

For Korff AG, the choice between primary aluminium and recycled aluminium depends on the material properties and technical requirements of the respective product and application.

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

Aluminium recycling involves collecting, sorting, processing and remelting aluminium so that it can be reused as a material.

Aluminium recycling generally requires significantly less energy than producing primary aluminium from bauxite. However, the recyclability of a specific aluminium product depends on several factors, including the alloy, coatings, contamination and combination with other materials.

This is particularly relevant for the products of Korff AG, as aluminium foils can be coated, printed, laminated or combined with other materials depending on the intended application and therefore require different recycling processes.

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 aluminium is aluminium obtained from recycling processes. Depending on its composition and processing, secondary aluminium can be reused for numerous applications.

The suitability of secondary aluminium for a particular product depends on the required technical properties, purity requirements and intended application.

At Korff AG, the possible use of secondary aluminium therefore depends on the technical specifications and quality requirements of the respective product.

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.

Thermal insulation aims to reduce unwanted heat transfer between areas with different temperatures.

In thermal insulation applications, aluminium foil has a high reflectivity for thermal radiation and can therefore help reflect thermal radiation and reduce heat loss when used in suitable constructions.

Korff AG supplies aluminium foils and composite solutions for thermal insulation applications in construction, technical fields and industry where reflective or barrier properties are required.

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

XRF (X-ray Fluorescence Analysis) is a non-destructive analytical method used to determine the chemical composition of materials.

In XRF analysis, the material is exposed to X-rays, causing the elements it contains to emit characteristic fluorescent radiation. This radiation can be measured and used to identify the composition of the material.

In aluminium processing, XRF analysis can be used to check alloy composition, purity or coating thickness. At Korff AG, XRF analysis supports quality assurance and process control without destroying the sample being examined.

Y

Yield describes the ratio of usable finished product to the amount of material used in production.

In aluminium foil processing, a high yield means that a larger proportion of the input material becomes usable finished product. This can reduce material losses and scrap.

For Korff AG, yield is therefore an important production parameter for evaluating the efficiency of material use and manufacturing processes.

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