Carbonation tool temperature confusion? Are we doing it wrong?

[Truman42]

Over the few years I've been brewing I've come across many posts and discussions on using carbonation calculators and in particular what temperature to use when doing the calculation. There are those who say that you must enter the highest temperature reached during fermentation as this will determine how much residual co2 is left in the beer. Even if you cold crash to 2C you still won't absorb any co2 back into the beer. (I must say that this method seems to be the most popular used)

I've also read other posts that say you go on the current temperature of the beer at the time of bottling. So if you cc at 2c then you enter 2c into the carbonation calculator.

I've always gone with the first one and if I fermented at 18C and raised to 20C to clean up then I've used 20c. Ive also nearly always had over carbed bottles.

Anyway was discussing this with my dad on the phone tonight and he had been talking to a fellow brew club member who is also a chemist and came up with the following answer, which makes sense to me.

You enter the temperature your going to drink the beer at into the temperature section of the carbonation calculator.

It doesn't matter what temperature you ferment at because co2 will not stay absorbed in a liquid unless it's under pressure. Pour a beer leave it on the bench and it goes flat. Pour a beer and put it in the fridge and it will still go flat. Regardless of temperature it will go flat and lose all of its co2 if it's not under pressure.
So there is no residual co2 left in fermented beer and using the method of entering the highest temperature you fermented at is irrelevant and I'm quite surprised that so many people including myself use this.

Entering the temperature your beer is at time of bottling, eg 2C if you've cold crashed is therefore irrelevant as well.

You carbonate the beer to give it a head when your drinking it. So you want to enter the drinking temperature of the beer Into the carbonation calculator. So usually around 4c- 10c (depending on style and personal choice). When you prime the beer and secondary fermentation takes over your beer might be around 19C-25c. Co2 will come out of solution but be trapped in the headspace. But when you chill it down to drink four weeks later the co2 is going to be re-absorbed back Into the beer at a volume depending on how much you chill it.
So drinking temperature is the one you want to enter into the carbonation calculator.
Not highest fermenting temperature and not the temperature at bottling time.

Please if my theory is wrong I'm happy to be proved wrong. Like I said I read many posts on the subject with lots of conflicting information and it seemed as though the most popular method was to use the highest fermenting temperature figure. But that doesn't seem to make sense to me anymore and certainly explains why my beer is often over carbonated.

And for those of you who may already know this....then why the bloody hell have I never seen anyone mention this in the numerous posts on carbonation calculator temps that I've read? Would have saved me from many an over carbed beer..lol

 

[Sea_Eagle]

So there is no residual co2 left in fermented beer

When you take a gravity reading and drink it or just have a sample before bottling your brew don't you notice all the bubbles in it?
There is some amount of co2 in it.

 

[philmud]

Is it really correct to say that a liquid not under pressure will not retain some dissolved CO2? Based on your Dad's mate's theory, there is no residual CO2 in our beer before we carbonate it, and yet we factor this into our priming sugar calculations.
Just because it tastes/feels flat doesn't mean no CO2 is dissolved into the beer, just not enough to make it effervescent. If colder beer retains more CO2, it makes sense to me to use the highest temperature post fermentation, because it's at this point that the beer relinquishes the most dissolved CO2.

 

[malt_shovel]

Sorry but I believe yu risk bottle bombs with this idea. Henrys law around partial pressures means that in a sealed container such as your fermenter the disolved concentration of CO2 will try to reach equilibrium with the trapped CO2 in the headspace. You are right that if it were an open fermentation the disolved CO2 would go close to zero as it reaches equilibrium with the CO2 in the atmosphere. Lower temperatures allow grater concentration of CO2 in the confined headspace (Boyles law I think but regardless, volume of a gas is dependent on pressure and temperature). I use the final fermentation temperature before cold crashing as no additional CO2 is assumed to be generated and pressure equilibrium is maintained by air going through the airlock.Hope that explains it cleary enough and be careful of bottle bombs.

Cheers

 

[TSMill]

I assume by chemist you mean purveyor of jellybeans, condoms and cheap sunglasses?

 

[Truman42]

Sorry but I believe yu risk bottle bombs with this idea. Henrys law around partial pressures means that in a sealed container such as your fermenter the disolved concentration of CO2 will try to reach equilibrium with the trapped CO2 in the headspace. You are right that if it were an open fermentation the disolved CO2 would go close to zero as it reaches equilibrium with the CO2 in the atmosphere. Lower temperatures allow grater concentration of CO2 in the confined headspace (Boyles law I think but regardless, volume of a gas is dependent on pressure and temperature). I use the final fermentation temperature before cold crashing as no additional CO2 is assumed to be generated and pressure equilibrium is maintained by air going through the airlock.Hope that explains it cleary enough and be careful of bottle bombs.

Cheers

Ok well thats makes sense and I will certainly get my dad to pass this on to his chemist friend to see his response. (And yes he is an actual chemist not a purveyor of jelly beans etc..lol)

Except there would be no risk of bottle bombs using his method as you would calculate for 4C instead of 18C-20C and therefore use LESS sugar/dextrose.

As I said thats the way Ive always done it and it made sense to me, I calculate temp based on 18C-20C depending on my highest temp reached during fermentation.
This chemist guy apparently has always done it based on drinking temp and from what my dad said his beers are always carbed properly and he has won a few competitions in the club etc.

 

[malt_shovel]

I understand your example but someone fermenting cool for a lager but planning to serve warmer in winter could easily add MORE priming sugar if you ignore what is already dissolved. Also someone not reading your first post thoroughly could easily come to the conclusion that there is no CO2 after fermentation so should add more as well. It was ambiguous to me.
Cheers

 

[stm]

I think your chemist friend is wrong. Perhaps you are just overcarbonating all your beers. Maybe just try less priming fermentables/sugars.

The reason he is wrong is that the beer sitting in a fermenter ready to be bottled IS UNDER PRESSURE. Precisely, 1 atmosphere of pressure, or about 101 kPa or 15 psi. There is definitely CO2 in solution.

 

[sponge]

I noticed a bit of over carbonation in the beers I used english yeasts on in my earlier brewing days.

I then found out that a number of those yeasts I used are a bit stubborn and required some extra TLC to get them to FG.

Whether or not there's still a little unfermented wort left in your beers Truman, I'm not sure, but might be worth looking into.

Otherwise, if you are consistently overcarbing by a similar amount each time, don't change anything and just reduce your required carbonation level accordingly.

 

[danestead]

Sorry but I believe yu risk bottle bombs with this idea. Henrys law around partial pressures means that in a sealed container such as your fermenter the disolved concentration of CO2 will try to reach equilibrium with the trapped CO2 in the headspace. You are right that if it were an open fermentation the disolved CO2 would go close to zero as it reaches equilibrium with the CO2 in the atmosphere. Lower temperatures allow grater concentration of CO2 in the confined headspace (Boyles law I think but regardless, volume of a gas is dependent on pressure and temperature). I use the final fermentation temperature before cold crashing as no additional CO2 is assumed to be generated and pressure equilibrium is maintained by air going through the airlock.Hope that explains it cleary enough and be careful of bottle bombs.

Cheers

I'm with malt_shovel. I think you need to apply some thought and knowledge if you want to carb your beers perfectly. I think to just use the highest temperature the ferment got to would be incorrect because co2 is released continuously whilst the beer is still fermenting.

If say you did a diacetyl rest at 15 deg for 3 days then lowered the temp back to 10 deg to let the beer finish fermenting the yeast will release more co2 into that beer so I'd use 10 deg in your calculations to give the most accurate result. If however, you did your diacetyl rest for the 3 days then dropped the temp back to 10 deg but the beer had already hit FG, I'd say it would be more accurate to use 15 deg in your carbonation calculations.

It's probably only going to result in minor differences, but thats my understanding.

 

[Truman42]

Some interesing responses gents and certainly they all make sense. My beers arent always overcarbed in fact Ive noticed that my stouts and other dark beers are often undercarbed.

I probably need to do some experimenting with this.

 

[manticle]

If your beer is always overcarbed for your palate, wouldn't you just prime it less next time?
None of your theory makes sense to me. Co2 doesn't come out of solution instantly.

 

[Scooby Tha Newbie]

I've read this thread with an open mind,but I'm confused as hell. I've only bottled one brew I did my home work looked at many threads and bulk primed To the general conscience. I used a calculator to my best knowage I've not made bombs. Until I know different that is what I will follow.

 

[zarniwoop]

Co2 will come out of solution but be trapped in the headspace. But when you chill it down to drink four weeks later the co2 is going to be re-absorbed back Into the beer at a volume depending on how much you chill it.

I think this is one of the flaws in this argument, if this was the case that CO2 came out as the temp rose and then was reabsrobed as the temp dropped then when you opened a warm beer it would be flat, mine aren't so I'm not convinced.

When I primed my first brew I misunderstood the instructions and primed based on bottling temp which was ~4C owing to cold crashing, it was very under carbonated.

 

[rehabs_for_quitters]

When the ferment has finished and you cold crash or lager, it should not significantly alter the amount of dissolved CO2.
With priming calculators use the fermentation temperature, not the cold crash or bottling temperature to get the correct volume,
I think you are over thinking it a touch which is leading to the confusion

 

[itmechanic]

Under atmospheric pressure there is normally 1 volume of co2 dissolved in the beer after fermentation.

 

[boybrewer]

I agree with most of the comments . I just recently bottled using the priming calculator and typed in the highest ferment temp( which in fact fermentation had finished and the temp got up to 24*C ) and it gave me what I thought was a rediculous amount of priming sugar so I backed it off by about 20gms down to 145gms and now I have under carbed beer :blink: . With my experience in bottling I always prime with around 138 gms of priming sugar for pale ales and have found that the carbonation levels do vary but rarely had under carbed beer , with the highest ferment temp of around 18*C . I believe that there is some truth in using the highest temp that the fermenter reached for good priming levels in the beer and as some calculators warn you that if it looks too high for the style then use your common sense and reduce it . With home brew you always have to experiment and find what works best for you .


My 2c

 

[DoctorBob]

[SIZE=medium]My two cents……I am not sure quite what the factors are that beersmith uses in its carbonation calculator….but there are a few science basics behind carbonation.[/SIZE]
[SIZE=medium]Carbon dioxide is more soluble in cold beer than warm beer. This has a significant affect on the gas pressure required in the headspace above beer to get a desired amount of gas dissolved. For a 2.5 vol carbonation (ie 2.5L of gas dissolved per litre of beer) you need a carbon dioxide headspace pressure of approx. 8psi guage, ie 8psi above atmospheric (approx. 56KPa gauge) for a beer at 0DegC. For a beer at 20Deg C, to get the same amount of gas dissolved you need a carbon dioxide head pressure of approx. 29psi guage (approx. 200KPa). For force carbonation this is pretty much the only relationship that matters – set the reg, allow time for the dissolved gas levels to equilibrate with the gas in the headspace, and you should get the desired carbonation level.[/SIZE]

[SIZE=medium]For bulk priming / bottle priming the above is also true……however there are a few more factors. Firstly the system is sealed and of a set volume, so the universal gas law can be applied (pV = nRT, where p = pressure, V = volume, n = number of moles, R = gas const, and T = temp in Kelvin). Pressure is proportional to temperature in Kelvin…so the pressure of a gas in a sealed volume reduces with temperature. This does happen in the headspace of a sealed beer container, but the difference between 293K (20C), and 273K (0C) is 273/293 = 0.93, ie the temp is only reduced by 0.93 by dropping 20K, so the gas pressure would only be reduced to 0.93 of the value at 20C when dropping to 0C. The main reason that a beer opened at 20C has much more pressure behind it, is thus not down to the increased temp causing the gas in the headspace to expand (although this is a factor), but is due to much less CO2 being soluble at the increased temperature. [/SIZE]
[SIZE=medium]When bulk / bottle priming you want to end up with a pressure in the sealed container, that at the serving temp, gives the correct volume of co2 dissolved. Factors affecting this will include the size of headspace, the amount of priming sugar you add, and the amount of carbon dioxide dissolved in the beer at the end of primary fermentation. [/SIZE]
[SIZE=medium] At the end of primary fermentation beer does contain dissolved carbon dioxide, as the headspace is CO2 at atmospheric pressure. Charts I have from Briggs brewing text show that at 15C, with atmospheric pressure of CO2 above the beer it will contain approx. 1 vol CO2. At 20C it would be a bit less, at 5C it is more like 1.4 volumes, and at 0C about 1.8 volumes.[/SIZE]
[SIZE=medium]I am not sure what factors are taken into account in the beersmith carbonation calculator…..but a quick play shows for a beer at OC, to get a carbonation of 1.7 vol, you need to add no priming sugar, ie the calculator assumes 1.7 vol of carbonation prior to bulk priming, which is about what you would get when you chill a beer down to OC at the end of primary fermentation, prior to sugar priming.(see previous paragraph) If you then play with the temp and change it to 20C, you need to add sugar to maintain the 1.7 vol carbonation. So it looks to me as though the calculator assumes 1.7 vol dissolved CO2, prior to sugar priming, and then works on the basic relationship that for a given vol of co2, a higher temp will require a higher pressure to keep the gas dissolved, hence more sugar is required. More sugar is required for bottles than keg, due to the reduced headspace to liquid ratio.[/SIZE]
[SIZE=medium]Given all the above I would use the serving temp to calculate sugar priming rates. At the end of the day this is safer if you are not sure, and less likely to produce bottle bombs / overcarbed beer. You can always add a bit more next time if it’s not fizzy enough![/SIZE]

 

[danestead]

Doctor Bob,

That all made sense and I agree with pretty much all you say until the last paragraph where you say you would use the serving temperature.

I agree that you want to end up with a pressure inside your bottle that gives you a certain volume of dissolved co2 inside your beer at serving temperature. However, I believe the calculator on beersmith or promash or whatever you use, asks for a temperature to determine the residual co2 in the fermented beer. From that, it will calculate the amount of priming sugar to give you your desired volumes of co2.

So basicqlly, although I think you are correct in most of what you say, I think temperature part of the calculator is there to determine the residual co2 produced during fermentation at that temperature, rather than calculate the required pressure in the bottle to achieve a certain amount of dissolved co2 based on serving temperature.

 

[DoctorBob]

Ok, so as a last resort I thought i would read the instructions in the beersmith help menu........cheating I know, but hey......

Using the Carbonation Tool


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Select the Carbonation Tool from the Tools menu or ribbon.



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Enter the target number of volumes of CO2 which will determine your carbonation level. Most beers require between 2.0 and 3.0 volumes, though a few styles run lower or higher than that range.



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If bottling, enter the temperature of the beer when it is bottled (often room temperature). If kegging, enter the intended storage temperature for the keg (typically the temperature of the refrigerator you will be storing the keg in).



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Enter the volume of the finished beer



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If kegging, the tool will display your target carbonation pressure for forced carbonation. As an alternative you can also consider naturally carbonating your keg with the amount of corn sugar shown, though natural carbonation in kegs is rarely used today.



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For bottling, the corn sugar weight or alternatively dry malt extract weight to use for bottling the beer is displayed.




so for bottling you enter the bottling temp and the calcualtor basically accounts for the co2 dissolved at that temp, for force carbonation enter the storage temp of a keg, and i would presume for priming a keg you do the same as for bottling