I started home-brewing lager beer last year. I am using ready-kits and the first three times it went quite well.

Now, with the latest, I had a very strange problem. A couple of weeks after I bottled them up and put in the cellar I found some bottles broken. I tried to open other bottles and they had a LOT of "air" inside an a lot of foam came out.

What could have been happened? What are the possibilities of this behavior?

  • 1
    How exactly are you bottling? I've never really had this problem, but I let my fermentation go for as long as possible. A friend of mine was having this problem and I found it was because he was taking the priming sugar and putting it directly inside the bottles rather than dissolving it in water then putting it in the beer then bottling.
    – D J
    Commented Nov 18, 2010 at 17:11
  • Yes, I usually do the same as your friend. I put the sugar directly inside the bottle, without dissolving it in water first. But the previous 3 times it went well using this method, even if, probably, next time is better to follow your suggestion.
    – Drake
    Commented Nov 19, 2010 at 9:40

3 Answers 3


This often happens for 1 of 2 reasons:

  1. bottling too soon, as @LoganGoesPlaces suggests. This means the yeast has not finished consuming the sugar in the beer and continues to do so in the bottle which releases more CO2 than the bottle can handle. You can tell if the fermentation is complete by measuring the Original Gravity and the Final Gravity and ensuring the difference is what is expected from the strain of yeast you are using.

  2. an infection of some kind. I had that happen once, and the bottles shot foam everywhere. Infections are usually the result of missing sanitation.

  • If I remembered well the fermentation was very fast this time, but my father confirmed me that he checked the density and it had reached the value specified by that lager suggestions. Is it possible that fermentation had stopped for some reasons even if the density value was correct (too hot maybe) and then it restarted inside the bottles?
    – Drake
    Commented Nov 18, 2010 at 8:31
  • Well, technically you're starting up a mini-fermentation to bottle condition anyway. Were you able to smell or taste any of the beer from the foamy bottle? Does it smell or taste off in any way? That would be one indication of a bacteria.
    – sgwill
    Commented Nov 18, 2010 at 11:29
  • I taste it, and I can only say that it is maybe too bitter than usual but not bad smell. Even if, probably, I am not able to recognize the smell of a bacteria indication.
    – Drake
    Commented Nov 19, 2010 at 9:44

Bottles usually explode either because of bottling too soon before fermentation is complete or because too much primer was used.

  • 2
    to elaborate more on this, have you used the same primer each time (if its included in the kit, ignore this). Different kinds of primer require different amounts (Corn vs. Cane vs. Malt extract etc...)
    – mummey
    Commented Nov 17, 2010 at 18:09
  • I always used sugar as primer with quantities indicated by instructions.
    – Drake
    Commented Nov 19, 2010 at 9:45

It could also be due to the bottle itself. If the bottles being used aren't up to being used for bottle conditioning then they can explode. You could have been unlucky and ended up with a batch of bottles that have some flaws. But until the worst happens you can never tell.

Although in this case as has been noted it does sound like it could just be a case of bottling too soon.

  • Is there any reliable way to check bottles for flaws? Is an inspection by eye sufficient? Commented Jun 10, 2013 at 13:05
  • Judging by the length of time between the answer and your comment-question, it may be better for you to pose this as a new question, so folks can properly answer it in full context.
    – Scott
    Commented Jun 10, 2013 at 15:22
  • 1
    Some bottles exploded. The others gushed. I don't think the fault lies in the bottles. Some sort of fermentation took place in the bottles -- either bacterial, due to an infection, or there was an excess of fermentable sugars due to over-priming or incomplete primary fermentation. Commented Jun 10, 2013 at 15:29

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