What temperature is a rolling boil?

Question

At what temperature is water called at a “rolling boil”?
How long does it take until water is at rolling boil?

Answer 1

The scientists tell us the temperature of plain water when it is boiling is 212 degrees F, or 100 degrees C at standard pressure. So it will be very close to that unless you are on a super-high mountain or someplace else where the air pressure isn't what we are used to at sea level.

"Rolling boil" is an expression I have usually seen applied to very vigorous boiling of things other than plain water (like for example when you are making jam, you are boiling water with fruit and lots of sugar in it). However, plain water at a very vigorous boil will still be the same temperature as gently boiling plain water. The difference would be the intensity of the heat source you are cooking it with. If you add heat to your boiling water at a very fast rate, it will boil very vigorously. Gentler heating will make for gentler boiling, but same temperature once boiling starts.

As far as the time it takes to get to that boiling state, that also would depend on your heat source. A little portable camping stove sometimes takes a very long time to boil your pot of water, but a very hot roaring campfire will get it boiling right away. At home, your big burner would be faster than your small burner. So we can't really say how long it will take to come to any type of boil.

Answer 2

The boiling point of water is 100C at sea level (and lower for higher altitudes). It is the temperature where the water changes from liquid to vapor. At this point, the temperature can’t increase further until all liquid water hast turned to steam.

A “rolling boil” simply means that a lot of water changes to vapor (indicates by large bubbles and a lot of movement in the pot), a gentle simmer means a small amount. The temperature is always the same.

How long it takes to come to a rolling boil depends on the amount of water and the power of the heat source.