2 points before FG

[Lanky94]

I have learnt that some brewery's cold crash their beer a couple of points below final gravity before casking it.

What would a couple of points below final mean? The way I see it is the estimated FG is 1010 then they stop it at 1012 correct?

NEW GUY QUESTION ALERT!!

 

[Battleaxe]

I answered a question you didn't ask...

 

[TheRedDarren]

If you halt primary fermentation 2 points before fg, you can use the remaining sugars for secondary fermentation and carbonation. After cold crashing there will still be plenty of yeast in the beer that will start eating again once the temperature comes back up.

 

[geetee]

That's exactly it, the remaining two points correspond to the amount of sugars needed for priming. Sounds easy but takes a lot of practice, knowledge and consistent conditions to be able to cool and expect to get an FG exactly 2 points above target. This is even more difficult with smaller homebrewed batches without the full level of control breweries have over temperature but at least we can just add a bit of priming sugar if we overshoot.

The FG is estimated from the OG multiplied by the amount of fermented sugars determined by the mash temp. So if you have mashed at 67C expecting 78% fermentable sugars than your FG will be 78% of the OG. You also have to choose your yeast knowing its potential attenuation to actually achieve this level of control.
Example
OG1050 so 50 x 78% = 39 points fermentable sugar, deduct from 50 = 11 so target FG would be 1011.
Therefore you would aim to stop at 1013 to allow the 2 degrees for priming

 

[MyQul]

As Geetee says it takes a lot of practice to get it right and if you don't you could end up with bottle bombs

 

[TheRedDarren]

You can use a 'forced fermentation' or 'limit of attenuation' test to determine the potential fg of any given batch of wort.
I'm not saying it doesn't take controlled conditions or experience to determine fg in advance, just saying this is how some breweries can do so.

 

[Lanky94]

Thanks for the replys lads. Too many variables me thinks. I'll prob let my beer ferment out and prime with small amounts of sugar.

 

[geetee]

You can use a 'forced fermentation' or 'limit of attenuation' test to determine the potential fg of any given batch of wort.
I'm not saying it doesn't take controlled conditions or experience to determine fg in advance, just saying this is how some breweries can do so.

Yes that is the correct way to determine actual limit of attenuation for any given yeast with a given wort but how many home brewers do that?

 

[TheRedDarren]

Yes that is the correct way to determine actual limit of attenuation for any given yeast with a given wort but how many home brewers do that?

Quite right, I don't, (although I might start) I just let it do its thing and finish up.
I'm happy to batch prime and bottle after a two weeks or so in primary.