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Grandmaster Brewer
Dec 25, 2006
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Well , this one is the poster child for "did you turn your computer on?"
I have been brewing now for a little over 20 years. All for fun and light head without government tax...
Took my dortmunder to my homebrew club as my sample for the evening and got a reaction that I wasn't expecting.
They all found the brew to be contaminated with phenols but ones they couldn't put their finger on.
So after a lot of discussion and disection of my brewing habits the "DUH" step came out.
All these years I have been covering my brew pot to increase the boil. According to most everyone there, that is not a good idea. Who'd a thunk?
So I came up with an idea for the board...How about a DUH SECTION
for obvious but unwritten proceedures for the uneducated and new brewers? would have saved me a red face and 4 bottles that I had to take home... :-[
Yeah a sticky might work too, thanks for the tip by the way as I'm new to this and probably would have made this mistake.
All these years I have been covering my brew pot to increase the boil. According to most everyone there, that is not a good idea. Who'd a thunk?

OK Newbie here, I have been covering during the boil also.  Can someone explain why that's bad?  I am still working stove top so I cover initially to get the boil up but then remove for the majority of the 60-90 minute wort boil.

Anyone have more details on this?

Thanks ???
From John Palmers book, "How to Brew" I quote:

"Covering the pot with the lid can help with heat retention and help you achieve your boil, but it can also lead to trouble. Murphy's Law has its own brewing corollary: "If it can boil over, it will boil over." Covering the pot and turning your back on it is the quickest way to achieve a boilover. If you cover the pot, watch it like a hawk.

Once you achieve a boil, only partially cover the pot, if at all. Why? Because in wort there are sulfur compounds that evolve and boil off. If they aren't removed during the boil, the can form dimethyl sulfide which contributes a cooked cabbage or corn-like flavor to the beer. If the cover is left on the pot, or left on such that the condensate from the lid can drip back in, then these flavors will have a much greater chance of showing up in the finished beer."

And those DMS compounds are made until the wort gets below 140F or so, so don't cover the pot after the boil either.  Not until it's pretty chilled and you're letting it settle before transfer.

That's actually how I got into judging...first entry ever had DMS, and I had to Google it up. 
Here's a "Duh" moment... I've been using a brew calculator that tells me how much liquid for the mash and how much liquid I need to sparge. So... that's what I did. I don't have fancy kettles with gallon markers etched in them so my pre-boil volume was determined by how much I drew off the mash from those two figures (mash water + sparge water). I was reading a conversation where someone used their brew bucket, with it's gallon markers, to be sure they drew off an accurate amount of pre-boil wort volume. "Duh!" Just another step in learning how to brew more consistently.