If you ask anyone who is good at cooking, they will tell you that copper is a better conductor of heat than iron. In general, copper has a thermal conductivity that is eight times higher than that of iron and nearly twice that of aluminum.
With tamagoyaki, the egg solution directly touches the hot pan and causes thermal coagulation, so the game is won in a very short time.
At this time, if you put a square tamagoyaki pot on a round heat source and heat it, it is easy to cause unevenness in temperature depending on the part. In order for all the eggs to solidify in the same way the moment they are poured into a square tamagoyaki pot, the temperature of each part must be completely uniform.
For this reason, copper pots with high thermal conductivity are used.