Why Do Aluminum Pots with Larger Bottom Diameters Bulge More Easily?
It is common to go into the situation that your Aluminum pots become bulged form the bottom after some time us. Why this happen, and how we can avoid it to make the service life of pan longer. We will discuss it in details. Hope this would help you know it.
The main reasons can be attributed to ”uneven heating” and ”thermal stress.”
- The Heating Principle of Induction Cookers – Localized Heating
An induction cooker does not get hot itself. It generates heat directly in the Aluminum pot‘s bottom (via eddy currents) using a magnetic field. However, the heating coil within the cooker does not cover the entire cooking surface; its effective heating area is usually a relatively small circle. The problem arises when you place a pot with a base diameter significantly larger than this heating coil. - Significant Temperature Difference Creates Thermal Stress
- Central Area (Directly Heated): The central part of the frying pan or pot’s base, directly over the coil, is heated intensely and directly. Its temperature rises sharply, causing the metal to expand rapidly.
- Peripheral Area (Indirectly Heated): The outer edges of the pot’s base are not in the strong magnetic field. They heat up primarily through conduction from the central area, so their temperature rises much more slowly and remains far lower than the center.
- “Restriction” and “Struggle”: The metal in the center desperately tries to expand outward but is tightly constrained by the surrounding, cooler metal at the edges that has not yet expanded. This immense internal pulling force is known in physics as ”Thermal Stress.”
- Material Yielding and Deformation
When the thermal stress in the central area exceeds the yield strength of the pot’s metal material, the material can no longer return to its original shape. To release this enormous stress, the weakest point (usually the hot and stressed central area) is forced to undergo permanent plastic deformation—which is what we see as the pot bottom bulging outward.A Simple Analogy: Imagine tightly clutching both ends of a piece of paper and then holding a flame only to its middle. The heated center would try to contract (paper and metal have opposite thermal expansion properties), but your hands pull the ends to prevent it, eventually causing the center to tear. The pot bulging is a similar “thermal-mechanical” process, except the metal expands instead of contracts. -
Why is it worse for larger pots?
Because the larger the pot’s base, the greater the area and distance between the hot central zone and the cool outer edges. This makes the difference in temperature and expansion more extreme, generating greater thermal stress and making deformation more likely.
Other Risks of heating the pot with a big size bottom long time
Besides the pot bulging, using mismatched cookware poses the following risks:
- Significantly Reduced Heating Efficiency
A bulged pot bottom no longer makes tight contact with the cooktop, creating an air gap. Air is a poor conductor of heat, which drastically reduces thermal transfer efficiency. This leads to longer heating times and higher electricity consumption. You will notice the pot seems unable to get properly hot. - Safety Hazards
- Tip-over Risk: A bulged bottom acts like a ball, creating very poor stability. The pot may wobble even on a flat surface, and it becomes easy to turn over on a smooth glass cooktop. A slight bump or uneven distribution of food can easily cause the pot to tip over, leading to burns or fires.
- Uneven Cooktop Heating and Risk of Cracking: Heat cannot be effectively absorbed by the pot and is instead reflected back onto the induction cooker’s ceramic glass surface. This causes localized overheating of the panel, which can lead to cracking or shattering due to the extreme temperature differential within the glass itself. Although modern cooktops have overheating protection, the risk still exists.
- Damaging the Induction Cooker
Operating the cooker long-term under the high-stress load of “mismatched cookware” can cause its internal electronic components (like the IGBT power transistor) to overheat and age prematurely, shortening the appliance’s lifespan. - Increased Noise
Poor contact between the pot and the cooktop can cause increased “buzzing” or vibrating noises during heating, and may even produce “clicking” sounds, degrading the user experience.
How to Prevent It and Choose the Right Aluminum Cookware?
- Choose Pots with a Flat Base and Adequate Thickness: High-quality induction-compatible pots often feature a ”multi-ply clad base” (e.g., 3-ply or 5-ply). A thick base can store more heat and distribute it laterally across the entire bottom more evenly, effectively minimizing the temperature difference between center and edge to prevent deformation.
- Match the Pot Diameter to the Cooktop: The Aluminum sauce pan milk pot’s base diameter should ideally not exceed the maximum heating zone marked on the induction cooker, usually aligning with the size of the coil circle marked on the cooktop center.
- Avoid Empty Heating and Rapid Maximum Power: Heating an empty pot allows extreme heat to build up in a very short time,very likely to cause deformation. Avoid prolonged use of the maximum power boost setting.
- Check the Pot Base When Purchasing: Feel the base with your hand; a good induction pot base will be very flat and solid. Gently tap it; a dull thud usually indicates a thicker, more robust base that is less prone to deformation than a pot that produces a higher-pitched ring.
Post time: Aug-26-2025
