Beer Bottle vs. Can Head Space, Carbonation, and Conditioning

Question

I have brewed at least a couple hundred 5-gallon batches of ale over the last 20+ years. For the vast majority of these batches, I have kegged in corny kegs and force carbonated using 30 PSI and shaking for a few minutes, or more often in the last 10 years, by setting the regulator at ~12 PSI for a week.

For the last 3-4 years, I have been bottling more batches for a few reasons:

1. It is easier to send home with friends.
2. I can have more variety (not restricted to the two kegs that fit in the beer fridge). I served 7 different styles in bottles at last year's New Years Day open house.
3. I can vary the carbonation of each batch more easily (to match properly match the style). This is an issue when I serve from kegs because I have one regulator and therefore one pressure setting for my two kegs.
4. I don't have to run down to the basement (where the beer fridge lives) every time I want another beer; instead, I can have a few bottles in the kitchen fridge.

When bottling, I use 22-ounce bomber bottles. I prime a 5 gallon batch with, usually, 3.0-3.5 ounces (depending on style) of dextrose (boiled in a small volume of water, well-mixed with the beer in the bottling bucket). I fill the bottles with a half-inch diameter, spring-tipped bottling wand, such as this one. I fill the bottle until it is completely full or overflows just a little. When the filler is withdrawn, it leaves the perfect amount of head space in the bottle. In other words, the volume of the bottling wand up to the height of the bottle is a good match for the desired head space. I let the bottles carbonate for at least 7-10 days at room temperature.

I recently acquired a can seamer and 16-ounce cans (type 211 with 202 lids).

My questions:

1. Should I adjust the amount of priming sugar for 16-ounce cans vs. what works for me with 22-ounce bottles in order to achieve the same level of carbonation in the glass?
2. Should I adjust how I decide that the package is full when filling a can? In other words, does the cross-section of the filling wand times the height of a 16-ounce can create the right head space volume in the can?

Answer 1

Have you tried bottling AFTER you have it carbonated from the keg?

Should I adjust the amount of priming sugar for 16-ounce cans vs. what works for me with 22-ounce bottles in order to achieve the same level of carbonation in the glass?

16 / 22 = 73%. 100 - 73 = 27%. You can test and decrease your priming sugar by 25% and see if that's enough carbonation for you.

Should I adjust how I decide that the package is full when filling a can? In other words, does the cross-section of the filling wand times the height of a 16-ounce can create the right head space volume in the can?

I'm sure you can fill it all the way to the top. You'll get some head so stop there. When you put the lid on, it'll squeeze some head out. Remember not to overfill it or you'll waste beer. You don't want to underfill it either because you'll waste space.

Once canned, the head will decrease and you'll have less than an inch in the top of the can.

It's all about testing and see what works for you. Some beers you'll want more carbonation, while others less.

Answer 2

Summary

1. Some headspace is required, so there is some compressible gas to deal with volume changes in the beer due to temperature fluctuations (the liquid beer is relatively uncompressible).
2. Too much headspace has some potential drawbacks: wasted space, potentially too much oxygen (which in theory could damage the beer).
3. The exact amount of headspace (above the minimum required) does not affect the final level of carbonation that is achieved (although it may affect the rate of carbonation).

Specific Answers

1. No change in priming rate is required due to headspace differences that may occur in bottles vs. cans.

2. The exact amount of headspace is not a factor with regard to final carbonation levels. Using the filler volume as the amount of headspace in both bottles and cans seems reasonable.

Details

picobrewery.com has this to say about headspace:

Some brewers claim that proper carbonation will not occur without some headspace, and will overcarbonate with excess headspace. As it turns out, it is not true; it violates the concept of equilibrium thermodynamics. The Homebrew Digest back in 1996 describes some experiments run by Steve Alexander and Al Korzonas that prove this out. Check out http://hbd.org/hbd/archive/1938.html#1938-17 for example. As long as the beer still has some viable yeast, carbonation depends mainly on the amount of priming sugar, not on the headspace. Bottles with extra headspace will reach full carbonation faster, however. This is because the extra oxygen in the headspace allows the yeast a brief reproductive phase.

Despite these fairly well run experiments, people expect quite a bit of headspace. This is particularly evident in competitions, where up to 1½ inches is commonly allowed. In part, this may be due to the fact that most of the bottle fillers on the market leave extra room when they are pulled out of the bottle.

In my opinion, 1½ inches is way too much. Generally, good brewing practice calls for minimizing oxygenation during bottling, so you ought to keep the fill level high. . Any oxygen not consumed by the yeast will go into unwanted oxidation processes. These can degrade the malt flavor, resulting in a cardboard-like flavor, and can degrade hop aroma. The greatest risk in underfilling bottles is the risk of developing acetaldehyde. Acetaldehyde is the result of direct oxidation of ethanol, and has a foul solvent-like aroma and flavor that can make an otherwise good beer undrinkable. Acetaldehyde will invariably form if the fill level is below the shoulder of the bottle. Another risk of underfilling relates to bottle detonation. If the beer is incompletely fermented or overprimed, the bottles are much more prone to dangerous fragmentation.

If your filler leaves too much headspace, you ought to top it up before capping. Another trick is to leave the caps loose for half an hour or so. As CO2 escapes from the beer it will tend to flush oxygen out.

So, should you fill the bottle all the way up to the brim? No, since beer expands when allowed to warm up. Expanding beer creates unimaginable pressure (far more than overpriming) that will either break bottles, or at least will cause leakage out of the cap. The amount of expansion will depend on how stable you keep your storage temperature. Don't forget to add a bit for unexpected heat, such as leaving beer in your car, for example. I had one nasty experience where a bottle burst all over the floor of my car. Wow, what a stink!

I personally fill my bottles quite high. However, I've often gotten comments about high fills in competition even if I've left a half an inch. Thermal expansion requires about 1/8" (1/4" for 22 oz bottles) so I try to keep the fill between ¼" and ½".

Here are some of the relevant passages from the experiment mentioned above:

Dave Miller's books suggest that bottle fermentation of priming sugars is a quick process taking several days, but that much more time is required to get the CO2 produced into solution thus carbonating the beverage. I speculated that Miller was probably right, and that the amount of space at the top of a bottle, the head space, should effect the rate at which CO2 equilibrium is reached. Several people posted that this was unlikely since, from their experience, bottles opened early have neither excessive gas pressure nor adequate carbonation.

My conclusion is that the underfilled bottle clearly completed bottle fermentation and cleared more quickly than either the normal or overfilled bottles. The overfilled bottles took longer than normal (and aren't finished yet!).

Also note that the normally filled bottles did not complete fermentation nearly as quickly as the bottle with fermentation lock.

For some reason the priming fermentation itself takes longer when capped.

One explanation of the increased rate of priming fermentation with increasing headspace is that more oxygen is included in the headspace which it turn effects the fermentation rate. This argument requires that someone explain why the normal fill bottle take so much longer to ferment than one with a fermentation lock attached. Since the amount of headspace isn't vastly different and obviously most of the oxygen in the headspace is expelled thru the fermentation lock. Perhaps significant oxygen passes backward thru the fermentation lock !

The other explanation is that the normal fill bottle has higher average pressure throughout the priming fermentation than an underfilled bottle and that the pressure SOMEHOW reduces the activity of the yeast. Osmotic pressure?

Final Thoughts on Oxygen

The following is based on my personal reasoning and observations; is not based on any measurement of oxygen or oxidation.

In my mind, one of the benefits of bottle/can conditioning is that the process should remove all oxygen from the beer within a week or so. When active yeast has oxygen available, the oxygen is consumed. This means that any oxygen that is either dissolved in the beer during racking/priming/filling or present in the headspace of the packaged beer will be consumed as the priming sugar is eaten by the yeast to produce the desired carbonation.

My personal experience has been that I do not observe any of the symptoms of excess oxygen and the resulting oxidation in any of my bottle-conditioned beers, even if they have been stored for many months.