Probably the most common question about aluminum foil is where the shiny side should be, facing the food or on the outside. Well, why is one side dull and the other shiny? Once you start down the rabbit hole of wondering about foil, all sorts of questions pop up—who invented it in the first place, is it aluminum, and how is it made?
Robert Victor Neher is often credited as the person who invented aluminum foil, but his actual contribution was designing machines to create it efficiently. Heinrich Alfred Gautschi was producing a version of aluminum foil earlier than Neher, though his contribution is often overlooked.
Aluminum is the 3rd most abundant element found on the earth’s surface, yet it wasn’t until the 19th century that scientists were able to isolate and extract the metal, and it wasn’t until the early 20th century that aluminum foil was used for packaging. This post will go over the various events that led to it becoming indispensable in today’s kitchen.
How Aluminum Foil Began
Heinrich Alfred Gautschi received a Swiss patent for the book rolling process of manufacturing aluminum foil in 1905, several years before Neher received his. However, he doesn’t receive much credit from the manufacturer of foil. Most likely, this is because his manufacturing method wasn’t as effective as Neher’s.
Also, his company focused on the manufacture of other rolled products, including wire, rods, and other aluminum items. The first large order of his rolled aluminum was for snuff packs, a thicker aluminum. Next, Gautschi focused his aluminum production on cookware, kitchen appliances, and eventually aviation.
Robert Victor Neher didn’t invent aluminum foil but rather a process for making it more efficient. Specifically, he created the continuous rolling process for making foil made from aluminum (instead of tin) in 1910 and took out a patent for the process.
Aluminum foil manufactured with this process was made at a Swiss plant owned by J.G. Neher and Sons. The plant was located in Kreuzlingen, Switzerland. The following year Toblerone candies were being wrapped in aluminum, and a year later, another Swiss company, Maggi, used the foil to wrap soup stock cubes.
Neher was not thinking about food when he created a process to manufacture aluminum foil. Instead, he was interested in air balloon racing and thought the foil could make the balloons airtight.
At first, he tried using aluminum foil from Gautschi, but those strips didn’t work. It was only then that he endeavored to manufacture the product himself.
Aluminum Foil Gets a Patent
In 1910 he took out a patent in Switzerland, and in 1911 took out another patent in Great Britain. Then, after realizing the foil would not be efficient to use in sealing air balloons, he began to market the product to the packaging of food products.
Companies that bought his foil wanted to have packaging with their logos. So Neher constructed machines that made it easier to dye, emboss, and print on foil packaging.
Unfortunately, Neher died of the Spanish Flu in 1918. Nevertheless, the firm he founded continued to develop additional products, mainly laminating aluminum to cardboard, paper, and fabric.
First Known Use of Aluminum
We know that aluminum was used for medicinal purposes in ancient Egypt. Then, in the Middle Ages, cloth makers discovered aluminum could be used to lock or set dye colors into fabric.
Even though scientists began to suspect the compound being used contained metal, the Danish chemist Hans Christian Ørsted was the first to isolate it in 1825.
How Aluminum Is Extracted
After an aluminum ore is mined, aluminum can be extracted using either the Bayer process or continuous casting. The common ore bauxite is typically used to extract aluminum. The Bayer process, which was invented first, also extracted aluminum, but it was too expensive for large-scale production.
Twenty years later, Friedrich Wohler, a German chemist, managed to create particles of aluminum the size of pinheads. A decade later, a Frenchman, Henri Sainte-Claire Deville, modified Wohler’s method and created marble-sized aluminum lumps. Deville’s process made larger-scale aluminum extraction possible.
Extracting Aluminum Method Improves
However, extracting the aluminum was expensive, so scientists began developing a method to extract aluminum using electrical currents. Working on separate continents, Charles Hall and Paul-Louis-Toussaint Héroult developed a similar process.
This method of extraction became known as the Hall- Héroult method. Charles Hall, an American, patented the process in the United States and Paul-Louis-Toussaint Héroult received a French patent for the process.
How Did the Aluminum Industry Develop in America?
The aluminum industry began to develop in America when Charles Hall realized the commercial potential and started the Pittsburgh Reduction Company in 1988. Aluminum was used for industrial purposes then, and Hall’s company was renamed the Aluminum Company of America (Alcoa) in 1907.
Ironically, Neher wanted to use aluminum foil for hot air balloon racing, and in America the first use of aluminum was leg bands for racing pigeons. Another early use was for the packaging of Life Savers. In the 1940s, foil used for the kitchen spread widely. Another use of aluminum in the United States was the original TV Dinners, which were made out of aluminum.
How Is Aluminum Foil Made?
Aluminum foil is made by stretching sheets of 98.8% pure aluminum between lubricated steel rollers. The foil is made thinner as it passes through the rollers repeatedly. Aluminum foil production is a little bit like making pasta, except the raw product is aluminum, not flour.
Unfortunately, the rollers can’t handle household aluminum foil since it’s too thin (0.19 of an inch or 5 mm) without tearing the material.
A massive block of almost pure aluminum is rolled multiple times between giant steel rollers, decreasing the thickness of the aluminum block. As the aluminum is spread out, it becomes longer and thinner. The thickness is reduced even more as the foil is repeatedly run through the rollers.
Although it sounds simple, it’s not. The aluminum, for example, heats up as it’s rolled out and can stick to the rollers if it gets too hot. Thus the roller pressure must be carefully managed. Therefore, there are alternating hot and cold stages of the process.
Why Foil Has a Shiny Side and a Dull Side
If the rollers attempted to reduce the thickness to the required standard, the material would tear. Therefore, the final rolling is done by sandwiching two sheets together. During this step, the dull and shiny sides are created.
The force required to feed 5 mm (0.19 of an inch) thin aluminum through the cold rollers might easily break it. Therefore, the sheet is doubled. The sides that come in contact with the steel rollers get more polished, whereas the sides that touch each other remain dull.
Therefore, the only reason one side is shiny is because of the contact with the rollers. It has nothing to do with which side should be against the food you’re baking.
Does It Matter Which Side of Aluminum Foil Goes on the Bottom?
It doesn’t matter which side of the foil goes against the food because the method used to cook most food doesn’t rely on light. Instead, we use convection, not radiation, when cooking food in the oven.
To cook something, heat is transferred from one source to the food. One method of doing so is conduction. Conduction is the direct flow of energy from one molecule to another. This transfer occurs when molecules collide, similar to how one moving ball strikes another, causing the second to move.
So when we cook on a stove, the heat is conducted from the burner to the pot sitting directly on it.
Another method of heat transfer is convection. Convection is when we use liquid (like water) or a gas (such as air) to transfer heat. The liquid or air flows from one area to another, carrying heat. In an oven, the heat hits the aluminum foil and is transferred to the food. Since the baked potato (or whatever you are baking) isn’t being heated by light, it doesn’t matter which side is up.
Microwaves and Aluminum Foil
The transfer of heat through electromagnetic waves is known as radiation. For example, when you stand in the sun, you are warmed by the infrared radiation that travels from the sun to earth. Likewise, light bulbs, irons, and toasters use radiation to transfer heat.
Microwave ovens function by quickly spinning molecules and causing them to align themselves to the oscillating magnetic field. These oscillations cause molecules, such as water, to spin, and heat is produced as the molecules spin.
Unfortunately, cooking with aluminum foil isn’t a good idea. Because aluminum foil is thin, when food wrapped in it heats up, water transforms into steam, releasing energy. Because the food is wrapped in foil, this energy has nowhere to go. This causes the foil to heat up quickly, increasing the chance of catching fire.
How Aluminum Foil Affects Cooking
Although which side goes on the bottom of your food doesn’t affect cooking time. There’s a factor that does. The tighter you wrap the foil, the faster the food will cook.
This is because air trapped in the aluminum foil pouch may act as an insulator, reducing how fast the heat transfers. So wrap your food tightly before baking it.
Is There a Difference Between Tin Foil and Aluminum Foil?
The most significant difference between tin and aluminum foil is that aluminum foil is easier and cheaper to manufacture. When first manufactured, aluminum wasn’t traded on stock markets, and the price of tin fluctuated. Thus, it was harder to calculate the cost of manufacturing the foil.
Even though some still refer to it as “tin foil,” aluminum contains no tin. Although tin foil was used to wrap food, the advantages of aluminum caused the demise of tin foil.
However, most foil produced in the early twentieth century was made of tin. It was used in packaging, such as cigarette packs and chewing gum sticks, as well as for wrapping leftover food. The issue was that it gave everything it touched a “tinny” taste.
But aluminum manufacturers had to convince the foil users—the food manufacturers—to switch over. So Neher sent the manufacturers packaging machine specialists who showed them how to modify their wrapping machines to use aluminum instead of tin.
The “tin foil” used in restaurants and homes isn’t tin, even if some people still call it tinfoil. Tinfoil was initially utilized for industrial applications such as coating cigarette packets. On the other hand, Reynolds Wrap foil has been produced of aluminum since 1926.
Although Robert Neher is credited with being its inventor, he built on the work of other scientists and inventors. Notably, Heinrich Alfred Gautschi patented aluminum foil in 1905, but he and his inefficient process for making it are often forgotten.
- South Florida Sun-Sentinel: Everything You Need to Know About Metals
- Alufoil: About Alufoil
- de.Wikipedia: Robert Victor Neher
- de.Wikipedia: Heinrich Alfred Gautschi
- Culinary Lore: Aluminum Foil—Should the Shiny Side be Up or Down When Cooking?
- Spectator News: History of Tin Foil
- Britannica: Foil Metallurgy
- Scientific American: Bring Science Home–Microwaves