Bottling Temperature and Carbonation

[Rick_UK]

Hi guys

I've just used the Brewers Friend priming sugar calculator to work out how much I'll need to add to my up coming lager like ale. The caculator factors in the temperature of the beer at bottling as well as the volume and levels of CO2. What surprised me is how much the temperature affects the amount of sugar required for a given level of carbonation. Basically it's telling me I need half the amount of sugar at 3'C than I would at 20'C.

This seems odd to me and wondered if its a glitch in the calculator. However my last batch was primed at 3'C - after crash cooling and is definitely over carbonated.

Any thoughts appreciated

Rick

[keith1664]

The colder the beer is the more of the CO2 produced during fermentation is retained (the colder a liquid the more soluble CO2 is in it) and as there is already more CO2 in there you need less priming sugar. So no, not a glitch and it seems you have first hand experience that it's true!

[Rick_UK]

The colder the beer is the more of the CO2 produced during fermentation is retained (the colder a liquid the more soluble CO2 is in it) and as there is already more CO2 in there you need less priming sugar. So no, not a glitch and it seems you have first hand experience that it's true!

Thanks Keith. This never occurred to me but would certainly explain it. Where would the CO2 in the beer come from if it's finished fermenting though?

[IPA]

As Keith said

The colder the beer is the more of the CO2 produced during fermentation is retained

[Charles1968]

If you've crash cooled from a higher temp, you shouldn't be using 3 Celsius as the temperature as the beer will have degassed when it was warmer - use the pre-crash temperature. It's possible the beer hadn't attenuated completely when you primed the first batch. Crash cooling can cause several problems as it temporarily ends fermentation prematurely. It's better to let fermentation run a bit longer than crashing, especially with a lager.

[jimpy0]

If you've crash cooled from a higher temp, you shouldn't be using 3 Celsius as the temperature as the beer will have degassed when it was warmer - use the pre-crash temperature. It's possible the beer hadn't attenuated completely when you primed the first batch. Crash cooling can cause several problems as it temporarily ends fermentation prematurely. It's better to let fermentation run a bit longer than crashing, especially with a lager.

cheers youve just answered the question in my head as reading

[keith1664]

The colder the beer is the more of the CO2 produced during fermentation is retained (the colder a liquid the more soluble CO2 is in it) and as there is already more CO2 in there you need less priming sugar. So no, not a glitch and it seems you have first hand experience that it's true!

Thanks Keith. This never occurred to me but would certainly explain it. Where would the CO2 in the beer come from if it's finished fermenting though?

It's left over from the fermentation, how much is left depends on the temperature.

[Charles1968]

It's left over from the fermentation, how much is left depends on the temperature.

Rick didn't ferment at 3 Celsius though, so it's more complicated. The CO2 level will depend on the temperature before crash cooling.

[keith1664]

It's left over from the fermentation, how much is left depends on the temperature.

Rick didn't ferment at 3 Celsius though, so it's more complicated. The CO2 level will depend on the temperature before crash cooling.

I don't disagree with you, I was stating where the CO2 came from. The CO2 comes from the fermentation, how much is in the beer depends on the temperature of the beer at the end of the fermentation.

[Charles1968]

Fair enough. Assuming Rick crashed from lagering temps (10-12), there could well be a lot of residual CO2, though I would imagine a diacetyl rest a higher temps would let a lot out though.

[Rick_UK]

Thanks chaps - it's good to get the best homebrewing brains around involved!

Yes I did ferment with US05 at 15C for 2 weeks and it seemed fully fermented out - hydrometer was stable at 1009 for 3 days it is now lagering for a few weeks at 3'C. I assume it wont ferment any further at these temps even if there were any fermentable sugars left - which is unlikely given the hydo readings.

So if it's absorbing CO2 whilst it's cooling where is it coming from? The beer is just in a plastic FV in my brew fridge.

If I prime with the amount given at 20'C, assuming the calculator is correct I'll be looking at bottle bombs!

Rick

[keith1664]

Thanks chaps - it's good to get the best homebrewing brains around involved!

Yes I did ferment with US05 at 15C for 2 weeks and it seemed fully fermented out - hydrometer was stable at 1009 for 3 days it is now lagering for a few weeks at 3'C. I assume it wont ferment any further at these temps even if there were any fermentable sugars left - which is unlikely given the hydo readings.

So if it's absorbing CO2 whilst it's cooling where is it coming from? The beer is just in a plastic FV in my brew fridge.

If I prime with the amount given at 20'C, assuming the calculator is correct I'll be looking at bottle bombs!

Rick

The CO2 is already there, it's a by product of the fermentation and how much of it that remains in the beer is determined by the temperature of the beer.
The colder it is the more CO2 is retained.
Hence you'll need less priming sugar if the beer is fermented at 15 than you would at 20.
You're not going to end up with bottle bombs, just a lively beer.

[clarets7]

I found this link http://www.brewery.org/library/YPrimerMH.html as I too was wondering how the temperature could make so much difference. It seems that even if you crash cool, if there is still a blanket of CO2 over the beer there is a certain amount that will be absorbed back into it. Makes it quite difficult to work out correct carbonation it seems if you crash cool and leave it at that temperature for a few weeks.

[Charles1968]

It seems that even if you crash cool, if there is still a blanket of CO2 over the beer there is a certain amount that will be absorbed back into it.

I question that. Without pressure and an airtight container, the CO2 blanket is going to diffuse away into the air must faster than dissolve back into the beer. Also, there's very little of it in the blanket relative to the huge volume needed to carbonate a drink.

Rick should use 15 Celsius for his CO2 estimate. The only effect crash chilling will have had is to slow down degassing. Normally the CO2 in a finished beer will keep coming out over a few days/weeks until the beer is completely flat. If you crash chill it, the CO2 becomes much more soluble and bubbles will stop forming, slowing down the rate it degasses or even stopping degassing altogether.

So I reckon Rick's first batch was over-carbonated because he bottled when it hadn't fully attenuated. Lagers take a lot longer to attenuate than ales and might look inactive when there's still a bit of sugar hanging around. If you crash chill a beer that hasn't fermented out, the yeast will start up again i the bottle when it warms up a little. Lager yeast will carry on fermenting even at fridge temps, albeit slowly.

[clarets7]

I use a 33L bucket for fermenting, and usually brew 19L batches. As it's in the fridge in the garage, which is none too clean, I've taken to sealing the lid and putting an air lock on. I'm hoping that by the time it's finished and I cool it from 18C to around 4C to clear that all of the space above the beer is filled with CO2, so around 14L. If my maths is right then it only takes 11.4L of that to dissolve back into the beer to saturate it at atmospheric pressure. I'm not saying that will happen, just that the possibility is there for CO2 to be absorbed back into the beer.

I still use the fermenting temperature in the calculators, and have found that to be fine, but then I haven't done any lagers that have been chilled for three weeks. Most likely cause of overcarbonation though is as Charles has said, that it hadn't fully attenuated before cooling.