priming after cold crashing

[LordEoin]

Beersmith and hcb.org say to use the temperature at botting.
Knights of the Mashing Fork suggest it's fermentation temperature
brewersfriend says it's a mystery and use your own judgement.

I know that my few batches after starting cold crashing were all over carbonated when using my usual amounts of priming sugar which always worked fine when bottling at room temperature.
Then i started adjusting the priming sugar to what the calculators said, using bottling temperature and all was fine until my last batch which is pretty undercarbonated.

Can anyone shed some light on whether to use fermentation temperature or bottling temperature when calculating the amount of priming sugar?

[Qs]

I always use the ferm temp. I think you just have to be consistent, pick a method and then adjust your sugar as it suits you.

What and when was your last batch btw? I did a porter that took much longer to carb up than might paler beers.

[LordEoin]

the under primed beer is a dunkelweiss  and come to think of it i might have just got myself confused as I don't think i would have crashed that.
maybe i just messed up and put the wrong amount of sugar in by fluke mistake...

This is the one thing that's got me questioning myself with every batch for a few months now since i took notice of these calculators.
I just don't understand how chilling the beer will add more co2 into solution without the need for more to be introduced to the fv somehow.

But the difference between 20L to 2.3volumes at 2 and 20 degrees is double..
20L to 2.3vol @ 2°  = 56g
20L to 2.3vol @ 20°= 115g

[Qs]

Well I generally use between 120 and 130g of dextrose and I always cold crash.  I'm definitely not getting crazy over carbing.

[HomeBrewWest]

Lots of issues here. Its not always about what CO2 is introduced, its also got to do with CO2 retention.

Its a big issues across all beers (kits, extract etc). Posts on boards.ie say to ignore kit instructions, which may be reasonable advice on old kits, but not the new ones.

For example, Craft Range instructions should be followed pretty much exactly in order to achieve the targeted CO2 levels.

The problem is that if you ferment at lower temps and extent the fermentation period, then residual CO2 levels before priming are unpredictable. Its further complicated by the fact that cooler beers retain CO2 better than warm ones, but the longer they ferment the more CO2 is lost. Retained CO2 levels are much higher in cold beers where CO2 stays in solution . . . warm them up and all the CO2 does a speedy gonzales!

Tricky.

[LordEoin]

yes, that's right. but you cannot retain extra co2 if it is not there in the first place.
fermentation temp - going by the amount of residual co2 a week or two ago and assuming it's the same after cold crash
bottling temperature - going by the assumption that it's retaining more co2 than it was before cold crash.
Neither make much sense.

Does anyone know how the residual co2 is calculated for those calculators?
here's their equation: CO2 In Beer = 3.0378 - (0.050062 * temp) + (0.00026555 * temp*temp)
I just don't know where these numbers came from

[Will_D]

Not sure about that equation!

Does ot agree with:

http://www.engineeringtoolbox.com/gases-solubility-water-d_1148.html

[Sorcerers Apprentice]

Carbonation is governed by Henry's Law
This might give some insight
http://en.m.wikipedia.org/wiki/Henry%27s_law

[molc]

Here's a question. Why not bottle, carb and then cold condition? The yeasties will have done their work and your co2 levels will be locked in.

[Qs]

Cos you get more sediment in the bottle.

[molc]

Yeah of course, though I never find that an issue. Does that effect flavour or is it just more of a pain for cleaning?

[Qs]

I just find it hard to not stir that yeast back up when I'm pouring unless I leave a bit more than I'd like to. Its a bit easier to rack after a cold crash too, the trub is a bit more settled and compact. Plus I usually use a lot of dry hops and I want it to fall out of suspension before I bottle.