I always boil with the lid off my kettles (2 pots).

But I've been thinking lately about the design of commercial kettles. It seems that to more closely match a commercial boil, I should put about a 3-inch diameter hole in my kettle lids, and boil with the lid on.

There are a couple of things I'd need to watch out for:

  • Beware of SMM/DMS.
  • Harder to see a boilover coming.
  • Re-formlate recipes for changed gravity

But has anyone tried this and noticed flavor differences? How would you describe those differences?

  • Why would the gravity change from covering the kettle?
    – mdma
    Feb 20, 2013 at 22:03
  • 1
    I'm thinking about the fact that reduced evaporation will mean that my post-boil gravity will be much closer to my pre-boil gravity than it is now.
    – Jeff Roe
    Feb 20, 2013 at 22:16
  • I thought something similar a while back, but after research and experimentation I found that it didn't make an appreciable difference in a small-scale brew. The off-flavors I had identified in my brews turned out to be the result of other factors and not DMS (from leaving the lid on) like I originally suspected.
    – thanby
    Feb 21, 2013 at 13:47

2 Answers 2


I think you are missing some information. First of all, often what works for commercial brewing doesn't necessarily apply to the homebrew scale; and trying to replicating may have little to no meaningfully positive effect on the beer.

Second, the reason pro kettles are covered is because they are being directly vented outside to prevent the brewery from becoming super humid with the massive amount of water being boiled off. Not a real issue at the homebrew scale (see above).

Next, these covered systems often employ an air management system that no only helps remove the humidity from the brewery, but it also increases the efficiency of volatiles (like DMS) to be removed. That increase efficiency usually means a much lower boil rate as well. In fact many pro kettles barely achieve a rolling boil. Just a small amount of bubbles breaking the surface.

If you tried it I doubt you'd have a problem with DMS, but I certainly don't think you'll be making beer any better or worse. There is no evidence that I am aware of in the brewing literature that suggests a change in flavor or a flavor profile related to the covering of the kettles.


I do this. I have a two inch chimney that I use to channel steam out of my kitchen. The lid also helps maintain a boil with less heat, which is convenient for me. I did tests early on with six row and very pale pilsner malts to see if I would get any DMS issues, but I didn't. One of these days I'll get around to figuring out how to measure it quantitatively, but I am generally very sensitive to DMS and I've had no problems.

That said, I can't imagine particular improvements in the final product. It can be a process convenience in some circumstances, but I wouldn't expect any flavor differences per se.

  • I definitely agree on the convenience factor, and good ventilation is a necessity if you're brewing indoors.
    – thanby
    Feb 21, 2013 at 13:51

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