Rolling boil and escaping nasties

[Fylp]

Hey All,

I've had this question rolling around for a while. What constitutes a rolling boil? Is it on the verge of boiling over or is it having movement beyond a simmer?

The other thing is, how covered can a boil be? Half? Less? When doing my max capacity I need to keep the lid on half way to keep the boil beyond a simmer, is there any issues with this. I've been fine till now, but am I pushing it ?

Phil

 

[Ducatiboy stu]

Hey All,

I've had this question rolling around for a while. What constitutes a rolling boil? Is it on the verge of boiling over or is it having movement beyond a simmer?

Bigger than a simmer.

You will find initially that a good boil will boil over in a small pot, then dies down.

Many a brewer has been caught out when the kettle all of a sudden goes nuts

A rolling boil is just that. A boil that looks like its rolling around

The other thing is, how covered can a boil be? Half? Less? When doing my max capacity I need to keep the lid on half way to keep the boil beyond a simmer, is there any issues with this. I've been fine till now, but am I pushing it ?

Dont cover your kettle when at boil. You can cover it to get it there but once it starts to boil leave it open

Boiling removes certain bad compounds from both the hops and grains

Cant remember off the top of my head what they exactly are, but it is necessary to let them evaporate away

They are compounds to do with DMS etc..

Basically you want a good rolling/vigorous boil with a lid in the open

Good rolling boils also aid in break formation which leads to better more clear/bright beer

 

[Moog]

i read somewhere you can float a saucepan in the kettle and it gives the same effect of boiling with the lid partly on, but doesn't have the down sides of boiling with the lid on

 

[yankinoz]

A rolling boil is bigger than a simmer, but there is no advantage to boiling at a furious rate. Volatilization of DMS goes on as long as you have a reasonable rate of boiling. Arguably the agitation of a wild boil helps bring our hot break, but you can always skim foam and reduce what subseqietky becomes hot break.

Don't worry if your boil slows for a short time so long as you return the wort to a rolling boil to vaporize whatever DMS accumulated during the quieter boil.

You might do a Google vid search and find Youtube examples.

 

[wobbly]

Dont cover your kettle when at boil. You can cover it to get it there but once it starts to boil leave it open

Not sure this is totally correct. Braumeister manufacture and market a dome for their machines that reduces to open area quite significantly (around 75%).
On a number of the "Cheap Dicko" style domes where the opening is only 150mm this equates to around only 25% of the full open area of the 20lt Braumeister.
From that I conclude that it would be OK to boil with your lid 50 to 75% covering the boiler

Cheers

Wobbly

 

[Ducatiboy stu]

Yes. but it still vents

 

[dr K]

In my world a boil should be volcanic, just short of a boilover, at this rate no way do you need a lid on !!
Amonst other things a rolling boil helps reduce the levels of DMS pre-cursors. Simmering with the lid on is even worse than just simmering as those volatile pre-cursors just condense and drop back in..Depends on your thoughts and threshold to DMS though, certainly a small level of DMS is OK in many beers and does not concern slow-chiilers / no chillers(who will have higher chance of DMS).
Anyway DMS is quite volatile and can be scrubbed out to an extent during fermentation.
K

 

[manticle]

No chillers only have a high chance of dms if their malt is poor, they boil with the lid on, do a short/inadequate boil or get a particular infection.
Otherwise agree mostly - boil needs to be visibly agitating, lid needs to be off.

Big difference between simmer and boil.

 

[Coodgee]

First brew I did was with a Rambo burner and high pressure regulator. Went through 90% of a 9kg gas bottle in an hour. Now *that* was a rolling boil. Ended up with about 15 litres in the fermenter!

 

[manticle]

Yes. It doesn't need to get to Mars: just move. More people evidently need to work in kitchens.

 

[wobbly]

....- lid needs to be off.

This is not the experience or practice supported by the German designers of the Braumeister

Wobbly

 

[manticle]

Great. For those without a braumeister: lid should be off. This is the experience and practice of every brewer pre braumeister.

I have great trust in the german engineering that goes into the brau and confidently presume they have taken appropriate evaporation into their design. I look at them like I do festool - market leaders in design and product. Doesn't mean you can whack the lid on a pot and pretend you have a $2.5k german engineered system.
I'm mildly confused by your attempt at a point.

 

[wobbly]

I'm mildly confused by your attempt at a point.

The OP sort advise/comment on his practice of having the lid half on/off during the boil.
Most/all responses have indicated that it should be off
My point being that the Germans (Braumeister) think it is OK to boil with the pot opening reduced by around 75% (300mm dia opening reduced to 150mm dia opening)
Some may argue that you will get condensation forming on the inside of the dome which will drop back into the brew kettle and this may happen until the dome heats up but once you reach boiling point the metal surface of the dome is very hot (personal experience) reducing the likely hood of condensation forming and being an issue
Although reducing/covering part of the boil kettle opening (lid half on) may well fly in the face of the "experience and practice of every home brewer pre Braumeister" I assume the Germans know a bit more than most home brewers

Wobbly

 

[manticle]

Yes but they have designed a specific system that has been tested multiple times with every single thing taken into account. It's much more complex than lid on vs lid off. Whatever percentage of 'lid on' they have worked out in conjunction with the vigour of boil and anything else can't really compare to a pot and burner/stove/ots element.

It's not a case of x does it, therefore it's ok until you know and can replicate what x actually does.

 

[manticle]

I assume the Germans know a bit more than most home brewers

Wobbly

Note I said brewer, rather than homebrewer. Regardless feel free to advise that lid on is best across the board. Just do it in a German accent, wearing funny trousers, a stupid hat and eating a sausage.
Well engineered sausage of course.

https://m.youtube.com/watch?v=MNNCqAmZzTA

 

[Barge]

There would have to be a huge difference between boiling with the lid covering the pot at an angle of 90o compared to the copper hood (which is what I'm assuming wobbly's referring to), which would allow steam to escape with minimal condenstation.

Like manticle says

It's not a case of x does it, therefore it's ok until you know and can replicate what x actually does.

I half covered a pot about 15 years ago, making a heineken clone. Came out with this weird flavour so I researched and discovered DMS. I tested what 'cooked corn' tastes like by adding the juice from a can of corn to some XXXX gold I had. The beers tasted identical.

I've been sure to boil hard, long and uncovered ever since.

 

[BJB]

Very common brewery in Belgium or Germany.

 

[Barge]

I'm pretty sure the kettles at the XXXX brewery are similar as well. I just think it's reasonable to suggest that the geometry of that arrangement vs a lid covering the pot at right angles could have an impact on volatilisation of DMS precursors.

 

[MHB]

Very common brewery in Belgium or Germany.

Yes most breweries have stacks on mash tuns and kettles, and every one I have ever see has had an extractor fan and if you could look inside the chimney, you would see a drip collector that stoped any condensate from running back to the vessel.
All standard design because brewers all over the world know its important to stop condensate returning to the kettle and most of us don't want to work in a sauna.
Mark

 

[Ducatiboy stu]

The OP sort advise/comment on his practice of having the lid half on/off during the boil.
Most/all responses have indicated that it should be off
My point being that the Germans (Braumeister) think it is OK to boil with the pot opening reduced by around 75% (300mm dia opening reduced to 150mm dia opening)
Some may argue that you will get condensation forming on the inside of the dome which will drop back into the brew kettle and this may happen until the dome heats up but once you reach boiling point the metal surface of the dome is very hot (personal experience) reducing the likely hood of condensation forming and being an issue
Although reducing/covering part of the boil kettle opening (lid half on) may well fly in the face of the "experience and practice of every home brewer pre Braumeister" I assume the Germans know a bit more than most home brewers

Wobbly

It still vents. Just because they have reduced the opening doesn't stop it venting. Its the same as having a lid on partially.