boiling with lids

[robsan77]

I've noticed through pics that no one seems to boil with a lid? any reason why? as a lid would reduce loss and save on energy needed to keep a boil.

 

[Muddydisco]

You can use a lid to help reach a rolling boil but it needs to be off for the boil as the boil itself is removing some nasties that you don't want in your final beer. I'm sure Aleman, tubby or james will spell it out correctly But I Know you don't want to boil with it on! Laymans terms :thumb:
I await the full version

 

[unclepumble]

I boil with a lid, as I don't have much choice. my boiler only has a lid that is less than a 3rd of the top of the boiler.

I haven't noticed anything detrimental in my brews yet, however have only done 2 so far.


I would say though I think I lost less during the boil on a 150ltr brew than i did with a 25ltr brew with no lid.

Shane

 

[Aleman]

In the ideal world you don't want to boil with a lid as you want to get rid of DMS . . . I actually do boil with a lid . . . See my brew days at my website . . . but have about 10-15% open.

DMS has a very low boiling point (~35C IIRC) so you can boil with a lid for most of the boil and then remove it to cool, and by the time the beer is cool all the DMS has been driven off.

There are other things to be driven off however, plus boil overs are likely . . .. You reduce your evaporation rate, but only because it condenses back into the kettle . . . so the heat load is the same, and Ideally you need to reduce the heat load to provide better beer.

 

[robsan77]

. . . so the heat load is the same, and Ideally you need to reduce the heat load to provide better beer.

surely the heat load is not the same. The lid will reduce the evaporation because liquid is condensed back but it will also reduce heat loss therefore reducing the heat load.. or am i getting my definition of heat load wrong?

 

[tubby_shaw]

I've noticed through pics that no one seems to boil with a lid?

That's probably 'cos if there was a lid on there wouldn't be much to see in the pictures :lol:

I do actually boil with a lid on but, it has a 150 mm ish hole in it to allow volatiles to escape :thumb:
Using the lid allows me to keep 50L + of wort at a rolling boil with one 2.2kW element
And seeing as I was popping to the garage for a beer I took a pic whilst I was there

And as I fully remove the lid for the last 15 min of the boil (with both elements running) and during cooling I haven't experienced any DMS or other boil condensate related off flavours :thumb:

 

[Aleman]

. . . so the heat load is the same, and Ideally you need to reduce the heat load to provide better beer.

surely the heat load is not the same. The lid will reduce the evaporation because liquid is condensed back but it will also reduce heat loss therefore reducing the heat load.. or am i getting my definition of heat load wrong?

You are reducing your loss to evaporation but you are not reducing the evaporation rate . . . as some of what what evaporates condenses back into the boiler.

If you have a boiler rated at 2.5KW and you boil for 90 minutes the thermal load during the boil can be considered to be 2.5 * ( 90 /60 ) = 3.75 . . . In an uncovered boiler you can loose as much as 5L to evaporation which is 19% evaporation. . . .

If you cover the boiler you still have the same thermal loading, but your (false) evaporation rate may be as low as 2L (or 8%). The amount of heat energy that has been transferred into the beer remains the same at 3.75.

Of course if you use gas or control the boiler element with a power controller of some sort using a partially covered boiler will allow you to maintain the same boil vigour for less heat input . . . and a lower true evaporation rate.

In an ideal world you would be looking for an evaporation rate of between 10-12.5% an hour . . . indeed in commercial breweries, considerable cost savings can be made by reducing the thermal load on the beer and there is a lot of research currently in producing beers with a evaporation rate as low as 4% . . . Of course this actually requires a lot of extra equipment to achieve . .. as the wort (and whole hops) is actually pumped from the kettle into an external sealed boiler where it is heated (with no evaporation) and then back into the unheated 'kettle' . . . the pumping of the wort serves the same purpose of a full on rolling boil . . . extraction of bitterness. Often the main kettle is sealed and kept at a higher pressure (Giant pressure cooker) to further improve hop extraction rates . . . Volatiles are released by suddenly releasing the pressure at the end of the boil . . . the volcanic boil that happens when this is done 'scrubs' any volatiles that have been trapped in the wort.

 

[evanvine]

I sparge to 6 gals and boil (with lid off) to 5 gals, the brew length I want.
This normally takes 1.5 hrs, the time I want.
That's my 2p worth (apologies JB)

 

[robsan77]

Thanks for the detailed reply.
But having a lid on at the start will definitely help get to boil quicker therefore less thermal load?
But once boiling makes no difference, so having it off (the lid) is best to let nasties out. I guess that if I did loose a lot of water through evap that it could be topped up at the end with boiled water from a pan or kettle!

 

[unclepumble]

I have found that with my boiler, with several holes in the top, all fairly small, and a hinged section of the top, (about a 3/4rd).

When you get a rolling boil it is not too violate, with the lid shut & temp gets to around 110 deg C with no boil over and a nice roll, but when you lift the lid it rolls like billy O, & you need to shut the lid quick to stop it boiling over.

I am assuming it is holding a slight top pressure when used like this.

I have found I experience very little evaporation either.

But when I stopped the boil I lifted the lid and let it stand 30 mins before cooling.

I know about modern commercial kettles & EWB's as I work on them regularly,I have seen a calandria also but never in use.


Shane