Making the metal

Because Bauxite is one of the most common ores found on the earth, sources for refining this into an ‘alumina’ oxide are plentiful. Passing an electric current through this pure oxide material creates the metal we know, using a process called ‘electrolytic reduction’. The silver coloured metal can be made into alloys by the addition of small amounts of other metals which can change the character or performance of these alloys to suit particular applications. Aluminium foil consists of almost pure aluminium but, increasingly, new alloys to add strength or make thinner gauges of the material, can be found on the market.

Manufacturing of aluminium foil

Alufoil is made by rolling the material into very thin sheets. To be classified as foil this must be between 0.006mm and 0.2mm (200µm) according to the ISO definition. Two stages are commonly necessary: hot rolling is where ingots of the metal are heated up and rolled into coils of between 2-4mm. These coils are then cold rolled several times to reduce them to the required thickness.

A second method, continuous casting, eliminates the hot rolling phase by converting molten aluminium into a thick strip, which is very quickly made into the coil for cold rolling.

To generate the very thinnest foils, two layers are rolled together – which causes a difference in the two surfaces, one matt one shiny (the matt side is the inner surface during this double rolling process). The two layers are then separated and can then be slit to the required width, prior to processing into end products.

Making the metal

Today aluminium foil comes in many different formats – such as the addition of coatings or laminated with other materials – to give it a huge variety of characteristics. Packaging converters in particular need alufoil with good adhesion, printability, elasticity, as well as for embossing or etching.

Plain foil is often used in thicker gauges for containers, while thinner gauges can be found in domestic kitchens or as catering foil, for example it is now an indispensible part of modern BBQ cooking.

The mechanical properties of foil make it ideal as an insulator; conductor of heat or power; as a barrier to light, air and odours; as a flexible and strong wrapping or lidding material; it can even protect against corrosion. And the biggest plus? It is aluminium is fully recyclable, once made it can be used again and again without any loss of performance.