Which temperature for calculating priming sugar quantity?

[Meatymc]

I am ready to bottle my Czech Pilsner. Used the brew fridge so been temperature controlled throughout - currently sat at 3 degrees.

I've got the calculators, know my volume and the CO2 range (2.2 - 2.7) but am unsure which temperature to select. Seems to be some conflicting information out there with some stating fermenting temperature, some temperature at bottling and others at varying points between the 2.

As this has had a brew fridge tied up for 8 weeks and I'm intending storing until at least mid-Summer I'd be a tad annoyed if I cock-up on the priming

Any thoughts?

[Bad 'Ed]

I've always thought it was the fermentation temperature. Certainly the one time I've bottled when the beer is cold I calculated using the current temperature and the beer was underprimed. I could have messed up the priming, but I've never messed it up before or since.

[BenB]

It'll be the temperature of the beer at bottling because what you're accounting for is the change in the soluability of CO2 in beer to create 1 volume of beer IE you start with a given amount of CO2 in solution and that will depend on beer temperature at bottling time.

[MTW]

I tend towards the higher temperature end for that field of the calcs, at least setting it for the highest temp it's been at during any transfer (primary to secondary, or secondary to bottles/bottling bucket). The more transfers, the more degassing, and the more of that at higher temperatures. If you've crash chilled a beer in primary and are bottling it from there, adjust it down a bit. Experience is key!

[BenB]

Absolutely! I carefully adjust for beer temperature then fudge it to account for the fact that I'll have knocked a load of gas out of solution stirring in the sugar, syphoning off the yeast cake, going through the bottling wand etc. But I suspect those loses are fixed and best adjusted by targetting a slightly higher CO2 volume than pretending the beer has more CO2 than it does to begin with. The fixed loses will not be temperature dependent whereas the inital carbonation will be.

but hey- like I'm going to be able to tell 1.3 vs 1.7 volumes anyway

[Meatymc]

Cheers guys although still not confident of getting this right.

I've brewed to 3 gallon, fermented at 12 degrees, acc test at 16 degrees, into secondary at 10 and then reduced gradually to 3 degrees over 5 weeks (actually been on the go for longer than I thought. I'm bottling so lose a bit more gas.

So what would you use as the temperature to do the calc?

[Meatymc]

Right, loads more research and the same split in decisions whether highest temp or temp at bottling.

As I'm aiming for CO2 at around 2.5 that gives me a range of priming for 15L of 88g at the higher temp (14) or 60g at bottling temp (3). Posts from all over the web on a similar brew, re-working for the same target, vary between 100g and 58g. As I'd rather it be slightly over carbonated than under, I'm going to go for 80g and keep my fingers crossed.

Need to crack on with some ales now so going to be quite a while before I can put into practise anything learnt from this exercise on another Pilsner or similar - assuming they don't all explode of course!

[rpt]

I've never worried about the temperature. I just use between 80 and 120g in 23L depending on whether it's an ale at the low end or a wheat beer or lager at the high end. You can over think a lot of this stuff.

[Simonh82]

I prime based on the highest temperature my beer has sat at after primary fermentation has finished. I usually bump the temp up to 21oC at the end of primary and leave it there for 4-5 days before crashing to 3oC for a couple of days. The calculation should be based on how much CO2 is in solution, not the potential at bottling time, because even cold beer will warm up in a bottle in a few hours if stored at room temperature. At 21oc the CO2 will have come out of solution and as fermentation has finished it isn't going to suck CO2 back in to solution just because the temperature goes down. Unless the yeast are producing more CO2 it will stay at the same level until the priming sugar is added and the bottles are warmed up to carbonate.