Lid on or Lid off?

[Kev888]

I'm personally happy with the lid only partially on because it doesn't really inhibit stuff venting out, but I'm not so sure I'd be confident about actually reducing/restricting evaporation by very much. I could imagine that 'would' reduce the loss of DNS, though I'm not informed enough to guess if it'd be by enough to matter or not. Would be worth a bit of research first perhaps - it could actually make things worse.

Also, without reducing things down a bit I'd certainly struggle to hit my OGs (without recipe alterations anyway).

Cheers
kev

[EoinMag]

Mmmm, I seem to have sparked quite a debate.
The reason for my original post is I made a pils
clone which has a slight chemical taste and wondered
whether it was down to keeping the lid on during the
boil. My boiler will boil with the lid off I keep it on
to reduce loss of wort by evaporation. I read sometime
ago that placing a plastic bowl or plate on top of the
wort reduces the surface area meaning less evaporation?
Maybe I will give this a go.

For a Pilsener you should definitely remove the lid, lager malts are particularly susceptible to DMS and you should NEVER leave the lid on for that, it's marginal for an ale. In fairness though you've already answered your own question. The DMS will drop back in off of the lid and will not evaporate as much as it should, the taste that will remain is that of cooked corn or cabbage.

[Swiller]

Exactly EoinMag I will know next time.
You live and learn thanks for all the replies.

[Wolfy]

http://beersensoryscience.wordpress.com ... ryscience/
A timely post there and lots of sciencey stuff, but in regard to leaving the lid on your boiler it has this to say:

If there is no way for steam condensate to escape from your kettle (like if your homebrew pot is covered during the boil) then that condensate will drip back into the wort returning that DMS back into your beer

... but read the entire article and make up your own mind.

[boingy]

It's hard to describe tastes but I'm not sure your "slight chemical taste" is DMS.

[Swiller]

Neither am I boingy there is no chemical smell
to it just a taste I am wondering or rather hoping
it may go away with time but I have my doubts.

[EoinMag]

It's hard to describe tastes but I'm not sure your "slight chemical taste" is DMS.

Granted, but he is boiling with the lid on, surely he should eliminate that variable first?

[Kev888]

http://beersensoryscience.wordpress.com ... ryscience/ A timely post there and lots of sciencey stuff, but in regard to leaving the lid on your boiler it has this to say:

If there is no way for steam condensate to escape from your kettle (like if your homebrew pot is covered during the boil) then that condensate will drip back into the wort returning that DMS back into your beer

... but read the entire article and make up your own mind.

Good article! I guess there being 'no way' for the steam/condensate to escape would indeed be bad, but it doesn't imply that it needs to be completely uncovered either - there must be some sort of limit in between, where 'sufficient way' for the DMS to escape becomes insufficient. I certainly seem to drive off massive volumes of steam quite efficiently in 60mins, even when I only had a 6" lid; I can't believe the more volotile DMS should hang around in there whilst all that was happening, even if some did condense back in once or twice in the process.

But either way, as neither I or Boingy with his waste pipe have had DMS tastes I'm guessing this is actually something i needn't worry about in practice; I can't cover much more or I get boil overs... In fact the lack of such tastes has already proved that all is well... so why I'm worrying about it anyway.. Doh!

Cheers
kev