Levels of Boiling Wort – A Visual Reference for Homebrewers

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, but after hours of searching the internet on a few different occasions, I realized it didn’t exist.

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.



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


  • Reduce heat
  • Stir away surface foam
  • Mist cold water on the surface foam with a spray bottle

If you found this helpful, subscribe for more or buy me a beer!

  2 comments for “Levels of Boiling Wort – A Visual Reference for Homebrewers

  1. Dennis Brandon
    August 14, 2015 at 5:39 pm

    Very useful and definitive images.

    • Obsessed
      August 14, 2015 at 6:29 pm

      Thanks, Dennis!

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