Boil off?

[Andyhull]

Seems to me that from reading the posts that generally people lose between 4lt and 6lt to boil off!
Does this seem correct?

 

[calumscott]

Easily!!!

I've got mine set to 5.25l for a 90 minute boil and it's still not enough... I put it down to the surface area of the pot...

 

[Andyhull]

The reason i ask it because if i want to end up with 23 litres then surely i only need to start with 29 litres that will easilly/safely fit in my 33lt+ boiler!

 

[PD]

all depends on the weather and the size of your equipment..... :shock: :shock: :party:

big pots little brew cold weather
little pot big brew warm weather little boil off...
Its one of the things you have to find out during a brew....and then when the weather changers say back into winter you have to find again....

% evaporation should ideally be between 5 -15%

and the formula is ( according to Vossey ) 100/ A x B where A is your litres pre boil and B is litres after boil. take the result from 100% to see your equipment figure

 

[Andyhull]

Well according to that i need 6.67lt for boil off so would need to start with 29.67lt pre boil giving me 4lt of head space minimum!

I have test boiled with water at around 32lt and it didn't boil over, im not sure if this is due to the shape of the boiler though, as it tapers in towards the top so funneling the boil to the middle of the opening!!!

 

[wigwamheed]

Wort can get a bit more carries away than water, brewed yesterday with 6.5gallon for 60 min boil and first couple of mins into boil I had thick foam up to 8 gallon mark

 

[PD]

One of reasons bigger boiler is better boiler...........
I feel a lot more comfortable now with a larger boiler and lots of headroom to play with......I can relax.

 

[calumscott]

Hear hear!!!

It's good to have a big one.

 

[wigwamheed]

Same here was really glad of a 60 litre yesterday. Even so got a bit panicky could just see it growing before my eyes. Thankfully turning an element off sorted it :)

 

[Andyhull]

I have seen "on youtube" a guy with this happening to him.
He uses a spray bottle to calm it right down, he stood by it for about 2 mins until the danger time passed and all was well.

I see what your sayin though and duely noted! :

I will get a larger boiler pot eventually but for time being i may have to reduce my post boil to 20lts.

Big ones are over rated :whistle:

 

[calumscott]

First wort hops help too.

Get them in before the foam starts and they keep it in check. :thumb:

 

[PD]

I used a tea urn for my first boiler and stuck to 19 litre brews to give room for the wort to move about abit, wasn't any problem but as I say having 100 litre pot now ...is bliss....... :whistle: :whistle:

 

[jonnymorris]

Well according to that i need 6.67lt for boil off so would need to start with 29.67lt pre boil...

You'll loose a fair bit to hop absorption too. I need to start with about 30L to end up with 23L and it's not all boil off.

 

[bunkerbrewer]

You gotta measure it.

er, record your pre- and post boil volumes for every brew and you'll get better at predicting it. piddle's right, though, mine varies from 9% to 13% depending on the weather.

 

[Andyhull]

Rightyho, I'll have to check it when I do a brew.
I'll probably start pre boil with 28lt to be safe giving me 5lt + safety margin.

 

[kev]

You gotta measure it.

er, record your pre- and post boil volumes for every brew and you'll get better at predicting it. piddle's right, though, mine varies from 9% to 13% depending on the weather.

.....and boiler deadspace

I need to start with 55l to hit 40l on a normal brew.

That's made up off boil off, hop absorption and dead space. All adds up. Everyones system's different

K

 

[Andyhull]

.....and boiler deadspace

I need to start with 55l to hit 40l on a normal brew.

That's made up off boil off, hop absorption and dead space. All adds up. Everyones system's different

K

Ahh, i forgot about the dead space! :thumb:

 

[kev]

Most people do until they pour out 2-3 litres less than they hoped for.

I normally fill up a new boiler then let it drain fully. Pour what's left into a jug and measure the volume.....that's your deadspace.

K

 

[Andyhull]

i have already done the dead space test, i have almost exactly 1lt, just over.

 

[calumscott]

:lol: Yeah, me too but that's a clean test and it gives you not quite the right result.

Pour what's left after a boil into a jug and you'll see a bit of a difference!

Although we allow for absorption by the hops we don't allow for the damming effect they create around the strainer/scavenger. The siphon effect of my hop stopper runs out with way more than the 1l from my clean test left. Maybe I'm just impatient and don't drain the last bit slow enough...?

I'm going to start measuring over the next few brews to understand it better. Part of the volume left will be hop absorption, part of it break material, part of it true deadspace, and part of it the damming effect of the hops.

Anyone remember simultaneous equations? :lol: