Under carbonated bottles...

[Darren Wood]

The the last few batches of all grain (ESB, IPA, APA) the carbonation in my bottles has been underwhelming...

I've been using the Beersmith carbonation calculator to determine the amount of sugars required in my bottling bucket. 

Some background: I ferment in a temp controlled fridge: 3-4 days at 17c, then up to 23c for 10 days. At which point I move the (very clear & beautiful) beer to the primed bottling bucket. Bottle in 500ml glass bottles with standard crown caps. I age for 3-4 weeks (and increasingly longer due to afore mentioned lack of adequate carbonation)...

Any ideas? Should I add more yeast to the bottles? If so how much?

Thanks team!

[Peter Smith]

Upon completion of fermentation, a certain amount of CO2 remains in the beer. This amount of "residual CO2" depends upon the temperature of the fermentation. An ale fermented at 65°F will have 0.9 volumes of residual CO2 while a lager fermented at 50°F will have 1.2 volumes. To get the same carbonation in these two beers would require different amounts of priming sugar.

For the same weight, the various priming sugars generate different amounts of CO2. To add one volume of CO2, you need to add priming sugar at the following rates:

Priming Ingredient		Attenuation		grams/liter
		Apparent	Real
Cane or table sugar (sucrose)		-	100%	3.82
Corn sugar (glucose/dextrose)		-	100%	4.02
Dried malt extract (DME)	Munton & Fison	75%	60%	6.8
	Northwestern	70%	56%	7.2
	Laaglander	55%	44%	9.3

[JumpR]

I was having the same issues with bottle carbonation, and was using a fairly similar process.  Temperature controlled fermentation for ~2 weeks, cooling at 2 degrees for another 5 days or so, sometimes adding gelatine, and then bottling.  To combat this, I was ramping up the dextrose to a few volumes above what was recommended for the style.  I was using a flocculent yeast and when combined with the length of time in the fermenter I think I was dropping out a fair amount of yeast, meaning less was making it into the bottles.

I was also encountering some off-flavours after bottle carbonation and was fairly careful with my process to try and avoid oxidation.  I think the whole having to warm up to fermentation temp again for two weeks, combined with secondary ferment in the bottle (which definitely altered flavours of some of my beers) wasn't doing my pale / blonde ales any good.

I have now bitten the bullet and switched to kegs.  The kick I needed for this move was Ralph mentioning that he entered the same beer into a beer comp one kegged, the other bottle conditioned.  The kegged one placed and the bottle condition scored a lot lower, with judges noting poor carbonation.

I know there are a lot of people who can bottle condition and turn out fantastic beers, alas not me.