Aluminium foil or âtin foilâ is a product most of us use on a regular basis, for one reason or another. If weâre not wrapping up our sandwiches in it ready for lunch time the next day then weâre using it in our oven, to cook on. In fact there are considerably more uses for it than just the home based, cooking purposes. Aluminium foil is used in different sizes and strengths for a number of industrial purposes too, but just how is this miraculous substance made? Well, the How Is It Made blog is here to help once more!
Firstly aluminium in its raw from is extracted as an ore called bauxite which then needs to have the pure aluminium extracted from it. To begin with the ore is refined so as to remove impurities like iron oxide, silica, and water. This refining process is separated into four stages the first of which is the digestion stage. During digestion the bauxite ore is ground down and mixed with sodium hydroxide and then the mixture is pumped into pressurized tanks. The mixture of the sodium hydroxide, the heat, and the pressure within these tanks causes the break down of the ore into a saturated solution of sodium aluminate and the insoluble contaminants within the ore. All of this then settles to the bottom of these tanks.
Clarification is next, which is the process of sending the solution and its contaminants through a set of different tanks and presses. At this point specially designed cloth filters trap the contaminants within the solution to be disposed of. The entire solution is filtered again and then transported to a âcooling towerâ.
Next, the solution (which is now aluminium oxide) is moved into a large silo in which the fluid is âseededâ with crystals of hydrated aluminium. This accommodates the formation of aluminium particles due to the seed crystals attracting other crystals which are within the solution and as a result large clumps of aluminium hydrate begin to form. These are then filtered out and finally rinsed.
The final step within this process (known as the Bayer refinement process) is known as âcalcinationâ, which is the exposing of aluminium hydrate to extremely high temperatures. The extreme heat to which it is subjected dehydrates the material, leaving a residue of fine white powder otherwise known as pure aluminium oxide.
This aluminium oxide is then in turn âsmeltedâ to produce a pure form of aluminium, this process will be covered next week in; How itâs Made? Aluminium! Part II
Picture sourced from Flickr User: Modern Relics