Under carbonated bottles...

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Permalink Reply by Peter Smith on April 30, 2014 at 7:27am

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

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Permalink Reply by JumpR on May 5, 2014 at 3:03pm

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.

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