Boiling wort with lid on or off

just wondering should wort be boiled with the lid on or off? I have done it both ways but I think I read some where if you boil with the lid on you can get off flavors.

Lid Off!!!

+1

Learned this the hard way on my second batch ever back in 2003. We all know
that water boils quicker when you leave the lid on, so I thought that I would increase
the efficiency of my wort boil doing the same. Didn’t know that there was this little
thing called Dimethyl sulfide (DMS)
http://www.howtobrew.com/section4/chapter21-2.html
that forms during the boil and NEEDS to be boiled OFF.
If you leave the lid on, it goes back into the wort.

After bottling and waiting until it carbonated, I tried my first bottle. It tasted
EXACTLY like creamed corn, which is fine for creamed corn, but not for ale.
Two cases of beer down the drain because I refused to drink it and absolutely
refused to foist it off on my Bud/Miller/Coors-drinking friends.

In addition to concerns like DMS as noted above, recipes are designed to boil off a percentage of water so you arrive at a target original gravity.

Tests have shown that leaving the kettle at least 15% uncovered will allow DMS to dissipate. Partially covered is fine, fully covered is not.

thanks guys that’s what I though.

:?: does this still apply to extract users. I thought that the process of making dme and lme took care id the dms. cheers

Considering the number of recipes I’ve seen that include malt additions at 15m or flameout, and that most of them are ones that use Pilsen malt extract, I’m inclined to guess that DMS can’t be too much of an issue with extract brewing.

First batch I ever did I told my wife we had to boil the wort topless. She took off immediately and ever since I have always had a few quiet hours to myself when brewing.

:cheers: