Causes of a non bacterial gusher?

Any ideas on what would cause a bottle to gush that is not bacteria? The short background to this question is that I brew with a mate, we split the brew 2/3 - 1/3.

In my 2/3's I've never had a single gusher, but in my friends bottles he usually ends up with about a quarter of them gushing to some extent. I know it can't be bacteria because everything is the same up until the point he takes the sealed bottles with him home. Thus if it were a bacterial infection it should be even across the whole sample and not just affect his beer.

The only two factors I can think of that might be causing the difference are the temperature that he stores the beer at (although he claims that they stay around 18-20 degrees celsius, and mine carbonate at around the same temperature maybe a little higher). The other factor could be that he has a bit of a journey to get home from my place where we bottle, so the bottles are definitely jostled. However the bottles sit and carbonate for at least 3 weeks and still gush. He claims that if he puts them in the freezer before opening them and really cools them down they won't gush (but this of course kills the flavor).

Any beer doctors out there that might be able to diagnose these symptoms and help us with a cure?? Any help is greatly appreciated!

sounds like uneven priming sugar to me. I would try to use carb tabs. The other thing is it sounds like he may not be chilling them for 24 hours before opening. If the co2 is not absorbed it will act like a gusher sometimes.

If he chills them cold and then pours them he can always wait a few minutes before drinking them if he likes them warmer.

I had some similar problems with a highly carbed hef earlier this year (close to 4 vols). This is what I learned:

1) Temperature can make a difference. let it cool in the fridge for at least a day or two
2) Age longer. Same bottles gushed like crazy one week, then just a couple weeks later (and beyond) had no problems.
3) Size matters. 22s take longer than 12s. Like another week or week and a half.
4) Agitation? Undecided. My bottles go from the closet to fridge in my hands. I tried rolling the hefs on the countertop prior to serving, but that wasn't the primary problem.

So, give them a little bit more time in the fridge and see if the bottles continue to gush next week and the week after. There's a video floating around these forums somewhere with a day-by-day test of carbonation. Wish I knew where it was. It was pretty enlightening.

Bad karma

Oh - and one more thing - make sure the priming sugar is properly dissolved before adding it, and stir it in real good without splashing the beer around in your bucket. I tend to stir a few times during bottling to make sure the denser fluid doesn't settle to the bottom where the spout is.

Cheers, Thanks for the quick responses!

I'll definitely tell him to chill for 24 hours, sounds like when he puts it in the freezer this is a quick fix for that.

I'm skeptical to it being a priming sugar problem though because mine are from the same batch, selected more or less at random, but not having the same problem at all. The bottles we're working with are bigger 500ml (not sure what that amounts to 16-17 ounces) so that might have something to do with it. He also does open his stash a little earlier than I open mine, so I'll stress that aging will do a world of good. Still puzzling though that for my bottles I have no problem at all and that some of his gush. There has to be some kind of crazy factor that causes this.