Induction cooking is the most energy-efficient and speedy technique used to cook food. It allows instant control of food energy better than gas burners. An induction cooker uses induction heating for cooking.
For cookware to work with an induction cooktop, it needs to have a ferromagnetic material – something that a magnetic would stick to. This means that many types of cookware will not with induction.
And an aluminum pan or pot is one of those.
Aluminum alone does not work on an induction stove because of materials magnetic and electrical properties. An aluminum must contain an iron insert in its base to work with an induction unit.
To cut the long story short – you can use aluminum cookware on induction, but it needs to have a coating which can work on induction cooktops.
In this article, I will cover all you should know about aluminum cookware and what to look for when buying one
Is aluminum is a good choice for cookware?
Aluminum is lightweight, conducts heat well and is fairly inexpensive.
This makes it a popular choice for cooking (especially for people using gas stoves or electric cooktops).
Although aluminum is an excellent conductor of heat, the skin depth of aluminum is larger as it is non-magnetic. The current flows in a thicker layer in the metal and encounters less resistance. Less resistance encountered means less heat produced. The induction process will thus not take place in aluminum.
The electric current flows mainly at the skin of the conductor, between the outer surface and a level called the skin depth. Where the skin depth is smaller, the resistance of the conductor increases at higher frequencies.
At a skin depth of 24kHz, the resistivity of aluminum is 1.12( 10-6 ohm inches), relative permeability 1, and surface resistance is 0.051 ( 10-3 ohm/square).
How can Aluminum be used in induction cookware?
Aluminum is desirable in cookware due to excellent heat conduction and distribution. Because of this aluminum clad stainless steel is used on induction with an inner layer of aluminum and outer layer or stainless steel.
It is also referred to as tri-ply cookware.
The high thermal conductivity of aluminum makes the temperature more uniform across the cookware. It spreads heat quickly and evenly.
The preferred base of cookware is usually steel plate pressed into aluminum or a layer of stainless steel over aluminum.
Sometimes induction disks or invertor plates are used to use pure aluminum cookware over induction. But this technique is not very effective and takes a long time.
The base should be flat and smooth of any cookware to be used on induction. Notwithstanding, there will always be jagged valleys. These imperfect bases trap air between convertor discs which slow down the heat transfer from the disc to the cookware.
Nowadays there is also something called all-metal models. Panasonic Corporation has developed a consumer induction cooker that uses a high-frequency magnetic field and different oscillator circuit design to allow use with ferrous metals. The model was released in 2017 named met-all and aimed at commercial kitchens.
Another method of using aluminum on induction is to apply a layer of computer thermal paste on the bottom of the cookware and then place the cookware on the disc. This will fill the air gaps between the disc and the cookware effectively. The downside is that each time it has to be scraped off and applied again for another round of cooking.
Inside the induction cooktop lies a coil of copper. When an alternating current is passed through the coil of copper, it results in the generation of an oscillating magnetic field.
This magnetic field penetrates the base of the cookware ( which is why the material of the base should be ferromagnetic) and induces strong eddy resistive currents. These currents produce heat and are responsible for cooking.
The induced current can heat any type of metal, but the magnetic properties of the steel vessel concentrate the induced current in a thin layer near the surface, which makes the heating effect stronger.
In materials like aluminum, the magnetic field penetrates too far, and the induced current encounters little resistance in the metal.
Only that part of the induction cooktop remains hot which is below the cookware. The rest of the cooktop remains cool to touch. The cooktop surface is made of glass-ceramic material which is a poor conductor of heat. This way only minimal heat is transferred from the pot to the cooktop surface.
Method to check which material will work on induction
The heat that can be produced in cookware is a function of the surface resistance. A higher surface resistance produces more heat for similar currents.
It can be used to rank the suitability of a material for induction heating. The surface resistance in a thick metal conductor is proportional to the resistivity divided by the skin depth. Where the thickness is less than the skin depth, the actual thickness can be used to calculate surface resistance.
An easy method is to look for the wave sign or a horizontal zig-zag which is usually displayed in induction friendly cookware by many manufacturers.
Some have ‘inducktion” word written.
Take an ordinary magnet and place it near the base of the cookware on the outer side. If it clings, it is induction friendly. If the magnet grabs the pan softly, it may not be very successful on induction. If there is no pull on the magnet, it doesn’t contain the right metals and will not generate heat.
This is an easy method to check which of the cookware can be used on induction.
Side effects of aluminum
While aluminum may prove to an excellent choice for cookware due to its properties, there is a huge issue with it that you must know
Aluminum from a long time has been linked to Alzheimer’s. Aluminum as metal gets easily dissolved in food. The longer duration food is cooked or stored in aluminum, the more amount of aluminum gets leached into the food.
Acidic foods such as tomatoes and citrus absorb aluminum the most.
To avoid this, some manufacturers use the method of anodization.
Anodized aluminum cookware conducts heat as well as aluminum cookware and reduces leaching of aluminum from cookware into foods, particularly acidic foods like tomatoes.
Also, in case you’re using cookware that has aluminum but it’s coated with some other metal, then it’s fine to use it.
Ferrous materials such as iron and stainless steel have relatively high electrical resistivity. Because of their high resistivity, they produce heat faster and more efficiently than aluminum when the electrical currents are induced.
According to joules law, the heat produced is directly proportional to the electrical resistivity of the conductor.
The electrical resistivity of aluminum is pretty low along with being non-ferrous making it unsuitable for induction cooking.
However stainless steel or iron-clad aluminum cookware can be used quite efficiently on induction.
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