Aluminum foil is commonly used for wrapping delicate foods. If you have been around barbecue parties, chances are you must have seen the hot delicacies wrapped in aluminum foils. But why is aluminum foil used to keep the BBQ hot and fresh? Is it an insulator?
Aluminum foil has insulative and conductive properties depending on how it is used. Aluminum behaves like an insulator when it doesn’t reflect thermal heat. Air and water can’t penetrate aluminum foil, making it a formidable barrier to convection and evaporation. However, when in direct contact with hot material, aluminum conducts heat.
Aluminum foil is one of the most interesting foils you can learn about based on how it switches between being a conductor and an insulator. Read on to learn more about the exciting thermal behavior of aluminum foil.
What is Aluminum foil?
After oxygen and silicon, aluminum is the most abundant element on our planet. Aluminum foil is manufactured by rolling sizable aluminum slabs until their thickness fall bellows 0.2 mm.
While more commonly known as tin foil, aluminum foil is chemically different from tin foil. In fact, aluminum foil is the successor of tin foil.
In the mid-20th century, food manufacturers rapidly transited from tin foil to aluminum in food packaging, being that the former added a tin flavor to their edibles.
Physically, aluminum foil presents a matte side and a notably shiny face. This shiny surface emanates from the last pass, where the aluminum is extensively rolled.
Given the challenge of manufacturing rollers whose gap can sufficiently handle the foil gauge, two sheets are simultaneously rolled in the final pass.
Consequently, the thickness is doubled. Upon the subsequent separation of both sheets, you get a shiny exterior and a relatively duller inner side.
Why Choose Aluminum Foil?
Aluminum foil is versatile. Let us explore the most common niches where it finds use.
Aluminum is predominantly deployed for wrapping food. This is common in situations where you need to store items that you would warm later on.
Aluminum foil works excellently for food wrapping, given its impeccable tolerance for extreme temperatures.
More also, there is virtually zero chance of bacteria, light, and gas penetrating aluminum foil. This means that food wrapped in aluminum foil doesn’t deteriorate as quickly as its counterparts wrapped in plastic.
It is interesting to note that 75% of aluminum foil produced today is used for packaging food and cosmetics.
Aluminum foil’s flexibility means it can take the shape of just anything you wrap it around.
When winter comes, your home needs to trap as much heat as possible. And when it is summer, it needs to let go of as much heat.
Aluminum foils perfectly fulfill these duties when used as roof insulation. How?
Aluminum foil has high reflective capabilities. The bulk of the infrared heat attempting to penetrate the house during summer would be reflected back.
It is the same for winter when heat attempting to escape the house would be reflected back by the aluminum insulation.
The truth is, aluminum doesn’t individually boast outstanding insulative properties.
However, when reinforced with fiberglass or, better still, Styrofoam, aluminum becomes a very powerful insulator, particularly efficient in reflecting thermal radiation.
Most aluminum foils used in home insulation are adapted with air bubbles sitting in the middle of the exterior and interior layer.
These bubbles work well in trapping airflow, impeding the conduction of heat (or even convection) between both layers. This is further reinforced with the aluminum sheet itself preventing heat radiation.
Aluminum foils have also been deployed in manufacturing space blankets to keep people warm in outer space and electromagnetic shielding.
The question now is when and which type of aluminum foil can you use for wrapping food, and which can you use as cooking sheets?
This brings us to another section.
How to Determine Which Aluminum Foil to Use?
We will segment aluminum foil into three categories here, each with unique applications.
Standard Aluminum Foil
This foil’s thickness typically ranges between 0.5mm to 0.7mm. This aluminum foil is used for packaging lighter commodities.
Heavy-Duty Aluminum Foil
Here the thickness can get up to 0.9mm. This type of aluminum foil works great for modest temperatures.
Therefore, you can use them as cooking sheets or as linings for your cooking pans.
Extra Heavy-Duty Aluminum Foil
The extra heavy-duty aluminum foil can get as thick as 1.3 mm. It can tolerate extreme heat and fits in well for heavy wrapping where there is direct exposure to fire.
You can use this aluminum foil for lining your grill, say when doing your BBQ. You can also use them for wrapping rib slabs.
How Does Aluminum Foil Insulation Work?
The thermal behavior of aluminum foil is quite a dicey one. To fully grasp this, let us explore how the aluminum foil works for the various modes of heat transfer.
Aluminum Foil and Conduction
Conduction is the transfer of heat when objects are in proximity. Aluminum foil excellently conducts heat when in direct contact with a heat source.
The significantly reduced thickness of aluminum foil allows for unhindered permeation of heat. This explains why touching a BBQ (wrapped in aluminum foil) on a grill feels hot.
Aluminum and Convection
In convection, heat is transported through fluids. Aluminum foil is impervious to air and moisture.
This means hot water will not evaporate from a container wrapped in aluminum foil.
Aluminum Foil and Radiation
Radiation involves the electromagnetic transfer of heat. Sunlight is the most familiar form of radiation.
Few materials can rival aluminum foil when it comes to reflecting radiant heat. Virtually any radiant heat beam incident on an aluminum foil will be reflected back.
This means aluminum insulation will efficiently keep sunlight off your home or sustain the heat of your food.
Is Aluminum Foil a Conductor or Insulator?
Aluminum delicately mixes the features of an insulator and a conductor. These features are selectively demonstrated based on how aluminum foil is used.
For example, when aluminum foil directly touches a heat source, it will conduct. But then it works as an excellent insulator when reflecting thermal heat.