Aluminum foil

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Aluminum foil - glossy and matt side

Aluminum foil , and aluminum foil or silver paper is the name given to 0.004 to 0.02 mm (4 to 20 microns) thin film obtained by rolling of the raw material of aluminum is prepared. Aluminum foils are gas-tight and thus airtight, and after heat treatment they are soft and flexible. That is why they are widely used for packaging food and medicines . Due to the consumption of resources and the high energy requirements for the production of aluminum, the use of foil is sometimes criticized by environmentalists. Occasionally, aluminum foil is incorrectly referred to as tinfoil (tin foil).

history

The beginnings of aluminum foil production are associated with the names of a few entrepreneurs who formulated their goals in the years before the First World War and who in some cases accompanied them until the middle of the 20th century.

On April 15, 1905, the Swiss entrepreneur Heinrich Alfred Gautschi received the patent for the production of aluminum foils using the so-called packet or book rolling process . This process basically consisted of rolling a thin sheet of aluminum, dividing it into two halves, laying them on top of each other and repeating the process until a package of 64 sheets of foil was obtained. This made it possible to achieve a significantly greater tear strength and flexibility of the film than by thin-rolling just one sheet.

Since only relatively small foils could be produced in this way , Robert Victor Neher , who comes from Schaffhausen in Switzerland , developed a special process together with Erwin Lauber and Albert Gmür to ​​be able to roll out endless strips. For this process, he first filed a patent application in Switzerland on October 27, 1910 and, on the basis of this, another in Great Britain on September 15, 1911, for which a patent was granted on January 11, 1912. To produce these films, which were suitable for machine packaging of chocolate, box cheese or cigarettes, they founded the Dr. Lauber, Neher & Cie. in Emmishofen in Switzerland.

Also in 1910, Aluminum GmbH was founded in Teningen as an offshoot of a machine factory and iron foundry , which, with a license acquired from Gautschi, manufactured aluminum foils under the management of Emil Tscheulin using the packet or book rolling process. In 1912 a subsidiary of the Emmishofen company, Dr. Lauber, Neher Co. GmbH , located in Singen am Hohentwiel , where, for the first time in Germany, endless strips of aluminum foil were produced. The companies in Emmishofen, Singen and Teningen were merged to form Aluminum-Walzwerke AG (AWAG) based in Schaffhausen . After the death of Neher, who fell victim to the Spanish flu in 1918 , Hans Constantin Paulssen, who joined the company in 1920, had a major impact on the development of AWAG and its successor companies from 1922 to 1963.

For Gautschi and Tscheulin, the use of aluminum foil as packaging was not initially a priority. Neher and his colleagues also initially had other applications in mind, such as the lamination of balloon envelopes with aluminum strips.

In contrast, the Supf & Klinger stannic oil factory in Roth made its first attempts as early as 1913 to refine aluminum foil sheets by hand. In 1920 the Stanniolfabriken F. Supf & Bauerreis & Müller were founded, in which aluminum foils were refined on a large scale, especially for the packaging of consumer goods. However, the aluminum foil was not rolled itself, but purchased.

One of the reasons why the company in Roth was able to expand so quickly with the processing of the comparatively cheap raw material aluminum was because it was able to fall back on the experience with tin foil, the production of which had already started in 1877. Under the direction of Willy Supf , tin foil was colored and embossed from 1890 onwards. A further development was the printing of patterns and names on the tin foil, with which numerous products such as coffee, soup cubes, candies, pralines, Santa Clauses and Easter bunnies made of chocolate were packaged. The company Supf & Klinger supplied its foils to several European countries before 1900.

In the USA, aluminum foil was produced for the market from 1913. Some of the first customers were pigeon breeders who marked their animals with aluminum foil tape. The first cardboard boxes laminated with aluminum foil were used around 1920. The Reynolds Metals Company was involved in the development of aluminum foil in the USA, which was founded in 1919 by Richard S. Reynolds Sr. as the US Foil Company in Louisville (Kentucky) and initially produced foil made of lead and tin, and from 1926 also made aluminum foil for Manufacture packaging. Reynolds Wrap® Aluminum Foil is still a well-known branded product in the USA today , which is why Raynolds Wrap is a common synonym for aluminum foil.

In the factories in Singen and Teningen, aluminum foil is still produced and refined today. Both belonged to the Canadian aluminum manufacturer Rio Tinto Alcan (RTA) until 2010 and have since been taken over by the Australian packaging specialist Amcor Flexibles . The successor to the company founded by Gautschi is now part of the Alu Menziken Group , of which the Gautschi family was the majority shareholder until 2007. Today it belongs to the industrial group Montana Tech Components .

Manufacturing

Aluminum foils are mostly made from pure aluminum ( Al content 99 to 99.9%). For this purpose, so-called pre- rolled strips with a thickness of approx. 0.6 to 1.5 mm are cold-rolled to the desired thickness in several rolling steps ( passes ) . When producing very thin foils, two layers are rolled (double rolling ) . After rolling, the two layers of film are separated from one another. This method results in two different surfaces on the foils (glossy and matte). The reason for this is that the respective outer side comes into contact with the sanded rollers and is therefore relatively smooth, while the inner sides are only in contact with the other film and thus receive a slightly more roughened surface and appear matt.

During rolling , the aluminum solidifies as a result of the strong deformation , that is, the foil becomes hard and brittle. Subsequent soft annealing makes it soft and flexible again.

use

The aluminum foil used in the household is usually 10 to 15 µm thin and is usually sold on 30 cm or 50 cm (catering) wide rolls in different lengths.

Food can be packaged in aluminum foil so that it is almost impervious to light and thus has a longer shelf life. Since the wrapped food is also almost airtight, aluminum foil is often used to transport several different types of food. There is little exchange of aromas and only a small amount of moisture can escape, so the food only dries out very slowly.

The aluminum foil is also used for food preparation. When grilling , it serves as a support on the grate to prevent the food from charring. Potatoes wrapped in aluminum foil are also placed directly on the embers. Fish can also be cooked in aluminum foil.

Aluminum foil in use

Films with a thickness of 4 to 500 µm are widely used in industry, with these rolls being over a meter wide.

Aluminum foil is at the hairdresser to the hair dye used, and in particular for the dyeing of individual strands. There are aluminum foils specially made for this purpose in hairdressing supplies. Depending on your preference, they are available in different thicknesses and colors, smooth or embossed, folded, on rolls or as pre-cut strips. The aluminum foil is placed under the separated strand at the hairline. With a brush, the hair coloring or bleaching agent is applied to the hair that lies on the foil. The aluminum foil is folded over at the ends of the hair and folded over the strand so that the area to be colored is enclosed by the foil.

A curiosity was the production of emergency money in Germany during the inflation of 1923 . Instead of paper, aluminum foil was printed. Aluminum banknotes were produced in the aluminum rolling mills in Singen and in Emil Tscheulin's foil factory in Teningen .

Thermal insulation

For buildings, aluminum foils and materials coated ( laminated ) with aluminum are used because they also reflect heat radiation, for example. Various composite materials are used for this. The coatings are similar to most foils, but are sometimes 50 µm thick.

Problem foods

Food that is particularly acidic (fruit acid, acetic acid), basic (lye on unbaked lye pastries) or salty (salted herring) should not come into contact with aluminum foil.

With increasing contact time and contact area, more aluminum diffuses into the food. Caution is advised, for example, with puree, compote or puree made from apples, rhubarb, tomatoes, but also pickled cucumbers, sauerkraut, citrus fruits (cut), salted herring, marinades containing vinegar or fruit acids and lye pastries before baking.

Corrosion also takes place on contact with another metal. The effect can be seen when the aluminum foil turns dark to black or even partially dissolves. Conventional aluminum foil is not coated (despite the two different-looking sides), whereas beverage cans (for acidic beverages) or food packaging made from composite foils have a protective layer. An aluminum exposure of 60 mg per person and week is tolerable. If this amount is exceeded, demineralization of the bones or anemia ( anemia ) may occur.

Environmental aspects

The excessive consumption of aluminum foil is often criticized by environmentalists , since around 13 kWh to 16 kWh of energy are required to produce one kilogram of aluminum using fused-salt electrolysis . These costs can be greatly reduced by recycling , since only five percent of the production energy is required to process aluminum. The annual production of primary aluminum in 2001 was around 24.5 million tons worldwide, of which around 3.5 million were in EU countries and around 650,000 tons in Germany.

literature

  • Otto Ernst Sutter: Twenty-five years of aluminum foil production in Teningen i. Breisgau. Festschrift for Jan. 11, 1936. 47 S. Ill. Teningen i. Br. Aluminumwerk Tscheulin GmbH, 1936
  • Aluminum-Walzwerke Singen (Ed.): 50 years of Singen Aluminum. 52 pp., 1962
  • Ilse Benig: 50 years of aluminum foils. Publishing house for industry, business and transport. Mannheim 1963, p. 86, illustration
  • Wilhelm Mehl: The lower mill on the Roth. In: Museum Courier Roth 2: 7-22. Roth., 2002
  • Rudolf Weber: Weber's Pocket Dictionary Aluminum - The material from A to Z. 1st edition. GDA, Düsseldorf, 2007, ISBN 3-937171-20-7
  • Uwe Kreisel: Culture Key USA. Discover and understand other countries. Max Hueber 2003. ISBN 978-3190060009 , p. 216

Web links

Commons : Aluminum Foil  - collection of images, videos and audio files
Wiktionary: aluminum foil  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Swiss patent CH 33290 "Paper métallique"
  2. ^ British patent GB 20455 Improvements in the Manufacture of Aluminum Foil
  3. ^ Aluminum-Walzwerke Singen (Ed.): 50 years of Singen Aluminum. 1962
  4. ↑ Benig, I. (1963: 8)
  5. ^ Aluminum-Walzwerke Singen (Ed.): 50 years of Singen Aluminum. 1962. p. 9ff.
  6. ↑ Wilhelm Mehl: The lower mill on the Roth. In: Museum Courier Roth 2: 7-22. Roth., 2002
  7. ↑ Uwe Kreisel: Culture Key USA. Discover and understand other countries. Max Hueber 2003. ISBN 978-3190060009 , p. 36
  8. ^ Anke Vöpel: skin and hair hairdressing expertise. Europa-Lehrmittel, 2003, ISBN 978-3-8085-6592-6 , p. 174
  9. ↑ Aluwerk Singen (1962, p. 10 with reprint)
  10. ↑ http://www.oekobaudat.de/OEKOBAU.DAT/datasetdetail/process.xhtml?uuid=b29f31dc-bf1b-4214-98b4-fc2b52165a86&lang=de
  11. ↑ Can I use aluminum foil on all foods? ; Cantonal Laboratory Zurich, accessed on July 22, 2014.
  12. ↑ GDA : Efficient use of our earth's resources ( Memento of the original from May 18, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.aluinfo.de
  13. ↑ Asia-Pacific Partnership on Clean Development and Climate : Aluminum Task Force - Action Plan ( Memento of the original from July 25, 2011 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 188 kB), page 5, Table 2: 4.2 vs. 0.19 @1@ 2Template: Webachiv / IABot / asiapacificpartnership.org
  14. ↑ Seminar paper: Aluminum and silicon: from the deposit to use ( Memento of the original from January 30, 2012 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. (PDF; 540 kB). P. 10 @1@ 2Template: Webachiv / IABot / www.rz.uni-karlsruhe.de