Define Rolling Boil

The guys from Brew Strong, Jamil Zainasheff and John Palmer, have frequently referred to a “vigorous/rolling boil” followed by some descriptors to help clarify what it looks like. I wanted to find a visual of what they were talking about to define rolling boil, but all I could find were images of water boiling, which didn’t really help.

Here is a humble submission to the world of homebrewing. I’ve created a short video with some easy terms and definitions of the different levels of a boil. They range from level 1 to level 5. The idea is that if more people use these same terms, we’ll all be on the same page discussing the look of a boil without actually seeing it.

You can also see some animated images below the video to define rolling boil.

Level 1: Simmer

Occasional tiny bubbles breaking the surface

Occasional surface deformations

Level 2: Slow Boil

Dense tiny white bubbles coming up with deformations

Frequent surface deformations

Level 3: Rolling Boil

Constant tiny white bubbles causing surface deformations

Momentary bubble ring around surface deformations

Level 4: Vigorous Boil

Tiny white bubbles appear all over, not just under deformations

Constant simultaneous surface deformations

Level 5: Violent Boil

Bubbles break the entire surface

Surface deformations occur under previous deformations

Deformations are violent eruptions

Boil Over

Violent eruptions produce persistent foam

Foam covers the entire surface

Foam and eruptions overflow the kettle

Prevention

Reduce heat

Stir away surface foam

Mist cold water on the surface foam with a spray bottle

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