Carbonation in odd size containers

General Homebrew Discussion
1

I usually package in 2.5 gallon kegs. I am considering making a batch and packaging into 2 1-gallon kegs and a 0.5 gallon growler. Instead of force carbonation, I would use table sugar and natural carbonation.

My plan would be to fill each vessel and then carbonate with table sugar based on an online calculator’s recommendation for amount of sugar per vessel. Am I missing anything here? Does it matter that those calculators are for 12oz bottles and I am filling a different size vessel with a different volume of headspace?

PS. I have 4 2.5 gallon kegs and doing this would increase my capacity by 25%. I already own 2 1-gallon kegs and several growlers. I would make a beer intended for sharing and take it to different events as needed.

2

The Brewer;s Friend calculator simply asks for the total volume of beer and gives the the required weight of sugar, so I don’t think it matters.
I’ve only just acquired a couple of kegs and I bottle most of my stuff. The beer usually takes around 6 weeks t carbonate and condition.

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3

My experience with bottling has been that the size of the bottles greatly influences the level of carbonation. I had been dealing with carbonation issues that seemed to be linked to bottle size. As an experiment, I bottled a batch in 8 oz., 12 oz., 16 oz., and 23? oz. bottles. The 8 oz were under carbonated, the 12 and 16 oz. were about ideal with the 16 oz. noticeably more carbonated. The 23 oz. bottles were almost explosive in their carbonation. My theory is that amount of head space in each size bottle is approximately the same, but the 23 oz. bottle has 3x the amount of carbon dioxide because it has 3x the volume of priming sugar. I think carbonation level may be partially offset because the carbon dioxide production is most likey suppressed because the yeast are affected by the increased pressure.

4

I use the Lallemand Bottle Conditioning Calculator. It asks for volume, temperature, desired level of CO2, and type of sugar. It doesn’t consider headspace.

I use 12 oz longneck and 375 ml Belgian style bottles.

5

I looked into this some more.

Simple answer: The head space of bottles is generally small relative to the volume of beer being primed. So, the calculators online do not consider head space.

Longer answer:

I wanted to prove to myself that head space was generally irrelevant. I calculated the amount of glucose added to prime 53 bottles of beer to 2.5 volumes of CO2. If you assume the beer fermented at 65F online calculators say this beer would need 4.3 ounces of corn sugar to prime.

The relationship between CO2 volume and pressure is governed by Henry’s Law, stating that at a constant temperature, the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas in equilibrium with the liquid.

Henry’s law is used to make the carbonation charts we use to force carbonate beer with the set it and forget it method. 2.5 volumes of CO2 in beer at 37F requires a head space pressure of 10.7 PSIG.

If we assume that each bottle holds 12 ounces of beer and has 1 ounce of head space then we have 53 ounces of head space that needs to be at 10.7 PSIG when the beer is in the fridge at 37F with 2.5 volumes of CO2 in solution.

We can use the Ideal Gas Law to calculate the number of moles of CO2 needed to pressurize the head space. For our 5 gallon batch in bottles we need 0.12 moles of CO2 in the head space. That is 0.12 moles in addition to the CO2 in solution in the beer. The extra corn sugar required is about 0.4 ounces to add that gas for the head space. With no head space one needs 4.3 ounces of corn sugar to carbonate 5 gallons beer fermented at 65F to 2.5 volumes of CO2. With 1 ounce per bottle of head space one needs 4.7 ounces of corn sugar.

The extra 0.4 ounces sounds like a lot, but when you consider the inaccuracy in all of your measurements, it’s probably best to play it safe and not add the extra sugar.

However, if you are priming 2.5 gallons in a 5 gallon keg, you will need to adjust the priming sugar amount considerably. With 2.5 gallons head space and 2.5 gallons of beer carbonated at 2.5 volumes (assume fermentation temp 65F) one needs 4.4 ounces of corn sugar. While 2.5 gallons of beer carbonated at 2.5 volumes (assume fermentation temp 65F) with no head space requires 2.1 ounces of corn sugar to prime.

I attached a spreadsheet if anyone wants to use it or check my work.
Carbonation Calculator.xlsx (5.6 KB)

Remember this is just math. Your mileage may vary.

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