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Is the bigger the boiler always the better the steam?

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  • Is the bigger the boiler always the better the steam?

    Is it a rule that the bigger the boiler the better the steam? Or do some smaller steam boilers outdo certain other larger boilers?

  • #2
    How do you mean 'better'? Are you referring to dryness or the shear capacity and ability to steam a lot of milk at once?


    • #3
      Well, dryness really.


      • #4
        I would say not necessarily. If you have a boiler in which the water level is very high, you'll get wet steam. A smaller boiler that is correctly set up may produce drier steam than a larger boiler that isn't correctly set up.


        • #5
          There are a heap of intangibles. A boiler might be considered as somewhat like a respiratory system:
          • size = lungs which is more or less a measure of outright puff dependent on the aforementioned boiler probe location
          • steam valve diameter = windpipe
          • holes in steam tip = mouth.

          Using this analogy, a VBM Domobar Junior has more steam pressure at the tip than a Giotto due to the bigger valve and larger holes in the tip. It runs out of puff earlier than the Giotto though. A Domobar Super has roughly 80% more puff as it has a much larger boiler and the same valves/tip. A diadema Junior- long lasting steam with a smaller 1.3L boiler and small holes in the steam tip. Still enough puff for 2 milky coffees and great for those learning.

          The other influencing factors include thermal mass of the boiler. A Duetto III (late 2013-2014 update) has heavy end plate boilers and otherwise identical anatomy to earlier Duettos. The steam is much drier than the earlier models.

          If the steam has a long run from the steam boiler you can get condensation- wetter steam. If that run is insulated in the same machine, steam quality will generally improve. Insulate the boiler for an improvement. Add teflon inserts to the wand and it changes again. A swap of wand sides (Hello The Coffee Machinist) can also improve things dramatically if a shorter run is the result.

          All as clear as mud ain't it?