Homebrew: why do clear bottles carbonate better?

December 4, 2006 9:49 AM

Homebrewfilter: why do clear bottles carbonate the beer better?

My wife makes her own homebrew, which I happily consume. We've noticed that the beer which is bottled in clear bottles will become more carbonated and have a better head than that in green bottles (and brown bottles, I think, though I wouldn't swear to it). This seems strange to me, especially considering that the bottled beer is supposed to be kept out of the sunlight anyway (we keep it in a dark cupboard).

Does anyone have a chemical explanation of what's going on? In terms of the amount of sugar added before bottling, how fine is the line between the green bottles turning out too flat and the clear bottles exploding? More generally, how can we acheive a uniform carbonation, or at least minimize the amount of beer that ends up flat-ish?

posted by louigi to food & drink (19 answers total)

I have a pretty hard time believing that the color of the glass could have an effect on carbonation level - even more so if you're keeping it in the dark. The reason most beer bottles are brown is because brown glass blocks the wavelengths of light that most react with hop compounds to cause the "light-struck" or "skunky" off-flavors. But I can't think how that might affect carbonation.

Are you certain the color of glass is the only variable? Like, have you tested individual batches, such that you're priming all five gallons and all the beer is treated the same up until you bottle, and then only the color of the glass is different (no bottles in different parts of the cupboard, so they're sure to be at the same temperature, etc)? If you happen to have bottled one batch in clear and a subsequent batch in a different color, I'd lean towards batch-to-batch variation (even if the recipe was the same, as yeast vitality could be different) before the color of the bottles.

If flat beer is a consistent problem, your yeast may be spent -- try pitching a fresh vial of yeast with the priming sugar. Also, make sure your cupboard isn't too cold; your bottles should be stored somewhere no cooler than wherever the main fermentation occurred, at least until they've carbonated.
posted by nickmark at 10:03 AM on December 4, 2006

That seems very odd.

Are you sure the caps are sealing properly on the green bottles? I'd doublecheck that first.

A more complicated -- and less likely, I think -- explanation is that perhaps you're bottling beers in sequence of color (white, brown, green) and not mixing the priming sugar in well enough. The priming sugar may be suspended at or near the bottom of your bottling bucket and causing those first, clear bottles to have too much sugar in them and the latter, green ones to not have enough. Try mixing the finished beer and priming sugar a bit better.

[On preview] Or, akin to what nickmark said, maybe you're storing the bottles in separate locations (clear in a warm area, green in a less warm spot). A few degrees can make a significant difference in the time it takes to carbonate.
posted by cog_nate at 10:06 AM on December 4, 2006

I've never heard of clear bottles contributing to higher carbonation rates and doubt that there is any contributing factor related to glass color. Assuming the same conditioning time, differences can be attributed to:
Differing amounts of headspace in the bottles
Inconsistent mixing of your conditioning sugars (so some bottles get different ratios of yeast to fermentables).

I'd be curious to see your results if you took three bottles (1 brown, 1 green, 1 clear) and bottled them with the FIRST beer out of your secondary, and did the same with the LAST beer out of your secondary - taking care to give them all identical headspace - and then poured them all into the same style of glass (in the same manner, at the exact same time) to see if you still experience a difference.

You may see more carbonation in your longer conditioned beers, or you may not have finished your primary fermentation completely (this is main reason for bottle bombs, as I understand it).
posted by spock at 10:06 AM on December 4, 2006

I'm with Spock. Run an experiment.
posted by craven_morhead at 10:21 AM on December 4, 2006

This is probably due to other factors, like bottle shape. Perhaps you are putting more beer into the clear bottles since it's easier to see how full they are, which will result in higher carbonation.

I use both clear and colored glass in my brewing and have noticed no difference.
posted by chairface at 10:26 AM on December 4, 2006

Assuming all else is equal in your batch, I'd vote for the seals being different on the lips of brown vs clear. This is most likely because of differences in the manufacture of the glass.

When I (rarely) bottle, I usually put one bottles worth into a clean clear plastic soda bottle so I can guage the level of carbonation via the "squeeze test" and sedimentation. This has never failed me and all my glass bottles are brown.
posted by plinth at 10:37 AM on December 4, 2006

i'd 3rd or Nth or whatever the shape of the bottle as a more important factor than color. if all your clear bottles are of one make, it's possible you're getting a better seal. i haven't brewed in a year or so, but i was of the drink-a-commercial-sixer-and-recycle-bottles school, and some brands were ever so slightly off in terms of neck circumference. others were a snidge too short or too tall and fell between settings on my capper and just would not take a good seal. could be your clear bottles are just better suited to your capper.
posted by sonofslim at 11:01 AM on December 4, 2006

Another possibility is the cleanliness of the bottles. It's going to be easier to see if a clear bottle is well cleaned and rinsed.
posted by Good Brain at 11:08 AM on December 4, 2006

I always dissolved my priming sugar in some hot water first, then stirred it gently into the beer I was bottling.

Another thought, maybe the green/brown bottles have some soap residue which is killing the head and giving the appearance of reduced carbonation.
posted by glip at 11:44 AM on December 4, 2006

Well we have to keep hydrogen peroxide in brown bottles (rather than clear) to prevent the hydrogen and oxygen dissociating due to UV but I doubt that applies in this situation...
posted by alby at 1:01 PM on December 4, 2006

Are the clear bottles from the same batch of bottles, or of the same type? It could be that the finish on the mouth of the clear bottle is better from that particular manufacturer, batch, or whatever is giving a better seal. To really test the effect of glass color would involve removing the crown cap variable. Also you are giving a subjective view of it. You'd also want a method of actually measuring the CO2 produced rather than saying "Oh, a clear bottle, this is going to have better carbonation". The power of suggestion and all...
posted by Eekacat at 1:16 PM on December 4, 2006

Alby has a point. Beer in clear glass will develop nasty flavors in sunlight. So, an early 20th C. American ad ran, "Drink Schlitz in brown bottles and avoid that skunk taste." Added trivium: this was Ernest Hemingway's favorite ad.
But I doubt there is any effect on carbonation.
posted by CCBC at 1:30 PM on December 4, 2006

Huh, lots of homebrewers on MeFi. Cool. I would re-emphasize all the suggestions thusfar about checking disparities in bottle size and shape, and possible differences in the amount of priming sugar that ended up in each bottle, based on lack of stirring or something.

One minor quibble with nickmark's suggestion: If flat beer is a consistent problem, your yeast may be spent -- try pitching a fresh vial of yeast with the priming sugar. I think there's no reason to use a $6 vial of yeast just to carbonate; always have a packet of Munton's $1 yeast on hand for this situation. It won't be doing enough fermentation to alter the flavor significantly.
posted by rkent at 1:56 PM on December 4, 2006

Could it be that the materials used to colour the glass make the surface less smooth? If that was the case, then it would create nucleation centres for the CO2 gas to precipitate out of solution. Just a guess though, if it really the case that clear glass works better.....
posted by Boobus Tuber at 2:57 PM on December 4, 2006

My first thought was the tops might be sealing differently but spock's got a couple of good hypotheses there and the experiment seems like a good idea. I propose modifying the protocol a bit: do the same top/bottom of the barrel sampling, but measure and mark the bottles ahead of time so you know you're putting the same amount in each. Also add one more bottle to each sample run: a clear bottle that you've masked off with tape to rule out the possiblity that light has something to do with it.

Good brewing.
posted by Opposite George at 4:20 PM on December 4, 2006

The cleanliness angle is a good one.

I was also going to ask how you prime. Some people put sugar or extract directly into each bottle, where it is easy to vary the amounts without realizing it. Even with the "dissolve in hot water and add to secondary technique" incomplete mixing can result in differences.

Also, are you sure you are comparing beer from the same batch? (All answers assume that but, if it is your wife who is the brewer, are you sure that the different bottle colors are from the same batch/recipe of beer?)
posted by spock at 5:57 AM on December 5, 2006

rkent, that's a good point about the yeast. Usually the only time I pitch fresh yeast is for barley wines, which have been sitting in the secondary for 6-10 months, and will be in the bottles for multiple years. For those, I figure it's usually worth a couple bucks to use the same strain I started with. Maybe I wouldn't taste the difference, but I'd know, y'know?
posted by nickmark at 11:11 AM on December 5, 2006

Bottling a new batch tonight. Will be trying to keep track of all the suggestions above. Thanks, everyone!
posted by louigi at 10:07 AM on January 14, 2007

Update: Seems that the main thing is that we're using all sorts of different bottles, and some of them are harder to cap well than others. We're using roughly this kind of capper, and it seems that the mark of a successfull capping is a slight circular indentation on the top of the cap. Ensuring that the ring appears on all the bottles caps, and adding just a little yeast at the bottling stage, has solved our carbonation woes. Thanks, everyone!
posted by louigi at 5:58 AM on February 11, 2007