Boiling with the lid on. does it really make a difference?

Dan · Post by **Dan** » Wed Mar 05, 2008 1:03 am

I opened this thread in relation to a post in a thread by "Sills" about being caught out by not boiling with the lid off.

I have boiled many batches with the lid almost fully on. the evapouration rate has been within the usual expected range (10-12% per hour) and the boil has been very vigorous.

If evaporation is taking place through a crack in the lid, then am i right in thinking the volitile compounds mainly the old DMS are been carried away with the steam?

I cant say i have noticed any typical DMS flavours (which i seem to be able to detect in quite a few commercial cask ales)

Gurgeh · Post by **Gurgeh** » Wed Mar 05, 2008 9:00 am

If the DMS condenses on the lid and then falls back in the wort, would it not re-evaporate?

what fraction of the evaporate does actually condense on the lid?

assuming it is a very small fraction, then the DMS condensing a second time around would be that fraction squared....

as all things with brewing are about balancing various factors - would the improved* boil from having the lid partially on outweigh the potentially very small amount of DMS that it would keep in the wort?

*by improved I mean a more fierce boil for your KW or the same boil for less KW...

Post by **Aleman** » Wed Mar 05, 2008 9:33 am

IIRC The boiling point of DMS is something like 35C, as as long as the lid is above 35C DMS will be boiled off. During cooling . . . DMS production will continue until around 70C . . . at this point any lid (if fitted) should still be above 35C (I've considered insulating my lids . . . but have never got around to it)

FWIW I boil with a couple of lids with a 'chunk' taken out of them to allow volatiles to escape . . . . I may have experienced this harsh bitterness as I am sure that at the last NCBA meet it was my beer that was commented on as being 'burnt' . . . . Of course it could also have been the massive amount of hops that it had in it as well

. . . . I think I need to have further evaluation

Martin the fish · Post by **Martin the fish** » Wed Mar 05, 2008 9:34 am

I wouldn't want to boil with the lid on. I couldn't see what was going on. At this stage of my brewing i like to watch everything and see whats happening.

Martin the fish · Post by **Martin the fish** » Wed Mar 05, 2008 9:50 am

Er, whats DMS?

Martin the fish · Post by **Martin the fish** » Wed Mar 05, 2008 10:46 am

Very interesting link DaaB. Thanks.

Gurgeh · Post by **Gurgeh** » Wed Mar 05, 2008 3:06 pm

it's the predominant flavour in a can of John smiths

Gurgeh · Post by **Gurgeh** » Wed Mar 05, 2008 3:08 pm

DaaB wrote:Maybe not, what if an insoluble component which is carried away with the steam becomes soluble and is then reintroduced into the wort? (such as the isomerising of alpha acids)

Speculation there Daab, or are you suggesting that there may be an improvement in utilsation

Gurgeh · Post by **Gurgeh** » Thu Mar 06, 2008 9:22 am

fair enough! - that Mircin volatile or whatever it was.

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Boiling with the lid on. does it really make a difference?

Boiling with the lid on. does it really make a difference?