Once water starts to boil, is it best to turn the heat down to a gentle boil or?

Question

will vigorous boiling food or an boiled egg cook faster?

Who is right?

Answer 1

It is best to turn the heat down, and allow the egg to simmer.

- Vigorous boiling runs the risk of cracking the egg

- Higher temperatures mean less control over the rate of cooking, thus you can overcook the egg to produce sulphur rings (nasty green rings between the yolk and the white)

Answer 2

Once water reaches boiling it cannot get any hotter. So you should always reduce the heat to that required for it to gently boil, as any extra heat is wasted, it is used only to convert more water into steam.

That said, if you add something to the boiling water, you may have to increase the heat for a period, to bring the water back to boiling again. Once there, again, extra heat is wasted.

.

Answer 3

If you imagine that the water is static, and all the same temperature, you may think that a simmer would be the same, but it is very dynamic system and so;

    Yes, a vigorous boil will cook the egg faster. Water, of course, can only reach 212 degrees F, but steam can get much hotter, and those big bubbles rising from the bottom are full of hot steam, so the more big bubbles you get, the more steam gets to the egg . If you boil something that can only endure water at 212, you can still damage it from the higher heat of the steam.

Also, the physical mixing itself insures that all of the water is hot, and that the slightly cooled water nearest the egg mixes more quickly with the freshly heated water from the bottom of the pan.

However, this higher rate of transfer of heat energy to the egg comes at a price: the energy efficiency of the cooking process will definitely fall as much more heat energy is lost  into the atmosphere from the large increase in released steam.