Priming sugar vs Beer temperature for Bottling

[Kingfisher4]

Although I appreciate that most members package the finished beer in kegs, rather than bottles and therefore priming sugar is not relevant, I would appreciate some advice. Bottles suit me better, both in terms of space, investment and enjoying the wider variety of beers in stock.

I have recently started using proper temperature control (with a grainfather stainless steel conical fermenter). I can now crash cool after final gravity is reached. I tend to ferment at 18 to 20°C, although recent Belgians have been at 26°.

I then crash cool for 2-3 days to 6°. I then bottle. I calculate the priming sugar needed and dilute it, using 10 mls of the priming solution per bottle. I then crash cool for a couple of days to 6°. I then bottle. I calculate the priming sugar needed and diluted, using 10 mils of the solution per bottle.

My dilemma is what temperature should I use for the assumption of dissolved CO2 residual in my beer?

For example, in the recent Belgian batch at 6° the calculator suggested 1.38 volumes of CO2 whilst at the 26° fermentation temp it was 0.74. It would be more convenient to bottle at 6° where I can be quite confident the temperature is accurate rather than trying to increase the temperature again after cold crashing. I am also somewhat unconvinced that the dissolved CO2 will really have reached the calculated levels in a couple of days of cold crashing.
I like quite low carbonation and aim for 1.4 volumes CO2 In my British ale and 1.8 in the Belgian bottles. The calculated residual CO2 converter will make quite a difference to the quantity of sugar needed for priming.

I may be overthinking this, but do not like over gassed beer and I’m particularly wary about potential bottle bombs, as the bottles are all stored in the garage, with much more variable ambient temperature than would be ideal.

I have tried guesstimating halfway between the 2 temperatures ( e.g. 16 above for the recent Belgian) for assumed dissolved CO2, is that fair?

I'd prefer not to return the beer to fermenting temperature again before bottling as the heater is only 30 watts, may take a while and give an inaccurate reading as temp probe well below the heater level and obviously don't want to stir post crash cool to risk oxidation and re-suspending the dropped yeast.

[gr_baker]

The temperature used in the calculation should be the maximum temperature reached during fermentation since that will determine how much co2 is dissolved in the beer.

[Kingfisher4]

The temperature used in the calculation should be the maximum temperature reached during fermentation since that will determine how much co2 is dissolved in the beer.

Thank you, that seems to be the consensus in most comments I have seen before. The calculators’ instructions are a little vague and sit on the fence on the subject.
Consensus seems to be that although theoretically possible the amount of CO2 in the headspace in the fermenting vessel will not re-dissolve over the period of time of cold crashing to a huge extent. Is that everyone else’s understanding?

[Digby]

The temperature used in the calculation should be the maximum temperature reached during fermentation since that will determine how much co2 is dissolved in the beer.

Thank you, that seems to be the consensus in most comments I have seen before. The calculators’ instructions are a little vague and sit on the fence on the subject.
Consensus seems to be that although theoretically possible the amount of CO2 in the headspace in the fermenting vessel will not re-dissolve over the period of time of cold crashing to a huge extent. Is that everyone else’s understanding?

Absolutely. When the beer has degassed at the higher temperature during and after fermetation, most of the CO2 would have left the fermenter through the airlock or similar. It would be tricky for this to find its way back into the fermenter and beer.

There will be a small amount of CO2 that could dissolve back into the beer from the headspace as you cool it but unless the femeneter is sealed and under pressure this will not be worth worrying about.

Matt

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[Kingfisher4]

Really helpful, thanks. That will increase confidence in appropriate priming for the bottles.