congratulations, you have a very clean kettle/pot.
Bubbles in water need something to stick to, a break in water surface tension, to form proper, other wise they don't gather together in enough numbers to break out of the water.
Same thing happens for freezing, you need what is called a nucleation point, usually some sort of impurity (even just a super tiny one) for crystals or bubbles to stick to so they clump together. Once enough are together then they can break out of liquid water.
congratulations, you have a very clean kettle/pot.
Bubbles in water need something to stick to, a break in water surface tension, to form proper, other wise they don't gather together in enough numbers to break out of the water.
Same thing happens for freezing, you need what is called a nucleation point, usually some sort of impurity (even just a super tiny one) for crystals or bubbles to stick to so they clump together. Once enough are together then they can break out of liquid water.