Overcarbonation

[Crusader-Rob]

Hi all,

Just trying to esatablish the cause of overcarbonation, this is the first time for me.

an IPA at 5.4% (Based on the Smell the Roses IPA by Kelly)

I carbed based on beersmiths to 2.55 volumes at 20 litres, i had 19 litres instead, so thats probably part of it, but based on calcs, it should be around 2.7 if thats the case. Now I'm actually getting gushers, and its ridiculously bitter due to the high carb. aroma is fantastic.
I do not believe the beer has an infection, based on taste, what is the more likely cause here ?

1- Residual CO2 from cold crashing, which has absorbed into the beer prior to bottling? If so, this is the first time I've has this type of issue. Cold crashied for 3 days with dryhop, awith 3 week fermentation and transfer to secondary after 10 days.

2- extreme heat in my garage, causing the yeast to over ferment in the bottles, if the beer was around 30 degrees. thats a temp guess, it could be more.

3- underattenuation (this is unlikely, as the beer went 1.055-1.012 and sat at that)

When batch priming, how do people calculate their figures, if acold crash is included? as the priming calculators suggest temps at bottling? I was told that the highest temps used is the target for priming?

Advice?Thoughts?Help?

2.55 volumes based on 21 top temperature, for 20 litres 126g of dextrose, which ended up being 19 litres.

[Smiffy]

I keg, so can't comment on the sugar quantity, but:

1) I have my IPA at around 1.7, much more than that and all I get out of the tap is froth.

2) I THINK that the baseline carbonation at the end of fermentation will depend on the temperature when the yeast was still producing CO2, so chilling after the fermentation has finished won't increase the carbonation.

[Ralph]

I have my IPA at about 2.7 volumes in my kegs. It is all about balancing the pressure/line length with kegs.

[Smiffy]

Yes the frothing depends on those as well as the tap itself, but being English I don't like highly carbonated ale either. But with my set-up, I have one short line with a restrictor (clamp) on it, and one longer thinner line, but I still find that slightly more carbonation or slightly more delivery pressure, and suddenly I'm getting a 4 inch head. but that's not what this thread is about anyway.

[Ralph]

CO2 dissolves in the beer when fermenting. If the ferment has finished (at whatever temperature you were fermenting at) and you cold crash, it should not significantly alter the amount of dissolved CO2... so in priming calculators you use the fermentation temperature, not the cold crash or bottling temperature. What temperature did you use when calculating and which calculator?

The figures you have given seem like they should give lower carbonation? 

You could test for the attenuation by pouring a hydrometer sample of the beer and letting it go flat and warm to 20 deg and then measure with the hydrometer. This will let you know if the beer has fermented lower in the bottle or not. This will give you info on whether the beer was not finished fermenting, or the yeast has fermented more while sitting at 30 deg.

[Crusader-Rob]

Thanks Zane, its quite frustrating, at 10 days it was carbed to where i wanted it, plenty of spritz vibrancy etc. I even got a whoa well done from the mrs. then 3-4days later, its all gone pear shaped...

I really need to sort my kegging system out soon, no more IPA's until I do... 

I was going to use the beersmith tab, but arranged my base recipe and stuck in the fermentation tab, ratherthan using the beersmith calculator. its very weird my last beer was carbed to 2.5 and its fine. same volumes.

the figures are 126g priming sugar into 19 litres of cold crashed beer.

i guess theres a possibility of a weight fuckup?

[Ralph]

Yep. Weight fuckup would do it. Do the hydro test. If it is where you expect (1.012ish) then I suspect that there was a weighing error. If it is infected or has fermented lower the FG will be lower.

[Crusader-Rob]

I'LL CRACK A BOTTLE TONIGHT. All bottles are in the fridge now, I've recapped a couple after releasing some pressure as well, seems to have helped a little bit on some bottles.

[Richard Rice]

Which fermenting temp should I use then?  I start at 17C, rise daily to 19C until nearly at terminal gravity, then raise to 21C until I'm happy fermentation has finished.  Then I cold crash. Mind you, the more I think about it, the more i can start to see reasons for the issues I've had.  My Kolsch exploded recently - but that was after months of bottle conditioning and I calculated the priming sugar at about 18C when the highest it got was 14C.  My recent Pale Ale, has only JUST carbed (at least 2 months) and I calculated that at 6C, which is what I cold crashed it to. Did a Digital IPA clone which I did'nt crash and calculated that priming sugar at a lower temp and it also turned into a fizz bomb; tho the more I think about it (flawed beer) it had lots of residual sugar from an incomplete/stalled ferment.  So what's the guts?  So if my beer sits fermenting at 19C for the most part, then only sits at 21C for two days at most, do I calculate at 19C or 21C?

[Ralph]

So... CO2 dissolved in the beer is a function of there being CO2 present to dissolve and the temperature of the beer. The colder the beer, the more CO2 can dissolve into the liquid.

If you hold a beer at a certain temperature for a day or two while it is fermenting then it should reach equilibrium of CO2 dissolved for that temperature. So if you do the whole ferment at 19 deg then you would use 19 deg. If you do 2 days at 19 and then 2days at 21 degs and it is still fermenting at 21 deg... then use 21. Basically the beer is able to hold less dissolved CO2 at the higher temperature, so if you sit it at a higher temperature for a day or two then use the higher temperature.

With crash chilling you drop the temperature of the beer, which means more CO2 can potentially be dissolved into the beer. As the fermentation is generally finished by the time you crash chill there is no more CO2 being produced and so it is unlikely that any more CO2 will dissolve in the beer... meaning that the dissolved CO2 should be at the same level as when you were fermenting, at whatever temperature you were fermenting at last.

Clear as mud?

Using the crash cool temperature (4 deg or so when it was fermented closer to 20) in a carbonation calculator should give you undercarbed beer. 

Using a fermentation temperature higher than where you fermented could give you overcarbed beer as in your Kolsch example.

[Richard Rice]

Well, in my last couple of brews that have turned out very nicely, the fermenting was at 19C for about 4 or 5 days.  In my most recent example, it only dropped one more point at 21C over 2 days. So, does 21C still stand in this example?  A previous beer, it had actually finished fermenting (that is, it didn't appear to drop any points during the 21C diacetly rest), so would 19C stand for this example?

Thanks for this, it's possibly the clearest, most concise answer I've had yet!

[Ralph]

If you stand at 21 deg the beer will lose some of the carbonation it had from sitting at 19 deg. It does not matter if it is actively fermenting or not as the dissolved CO2 is decreasing either way by the increase in temperature. If you stand at a higher temperature at the finish then use this higher temperature.

[Peter Smith]

yeah a friend has just advised putting an stc1000 on kegging fridge to keep temp more stable then the internal fridge thermostat.   its a big difference between 4-7 C if the co2 pressure doesn't change in keg system.

I always assumed the temp you use when bottle carbing calcs is the temp of the beer as you bottle it....  I had a dodgey stout infection produce gushers, and once had a wheat continue fermenting as well, that would have been my impatience