Over primed bottle-conditioning

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I wound up signing up here during my search for information on whether my over-primed beer might become a collection of unexploded bombs... And whether "Really Useful Box"s would be sufficient to contain any ...mishaps. Was going to make do with internet research, but I guess there's no harm in actually asking people who've got the experience and getting the information up for others in my position!

I actually made the account because I couldn't resist responding to a thread that was last updated in 2017 by the OP who said they'd tell us how they got on venting their 3x overprimed beer... I do hope they didn't suffer any lasting damage! But now I'm here to stay : ) Anyway - back on topic:

I've bottled, but slightly over primed...
  • Used Hacker-Pschorr 500 ml flip-top bottles
  • Empty bottles weigh 390 g with the top removed (to give some rough indication of strength)
  • Recommended sugar is 7 g/litre, so I contrived a measuring "spoon" to give me 3.5 g
  • Used Caster sugar
  • Dosed each bottle using a paper funnel and my "spoon" prior to filling
  • Re-measured my spoon once done for peace of mind and discovered it's closer to 4 g
My research suggests that flip-top bottles are typically good to 4 vol CO2, and the following calculator suggests I'm probably around 2.9 vols (Beer Priming Sugar Calculator | Brewer's Friend), so I think I'm safe. If I've overlooked anything though, please tell me!

Finally, does anyone have experience of containing beer bombs in plastic boxes such as the "Really Useful" brand? I've shifted my over-primed beer into an even sturdier plastic box and wrapped the bottles in a rug for extra safety, but it would be nice to know if my boxes have a good chance of containing any mess, and whether I should worry about our cats lying on the thick rug I've covered the boxes with!

Cats make good incubators, but I'd hate for them to be injured. Though to be fair, they rarely lie on the beer!
From what you've said I think you'll be fine. I've attached a pdf from Northern Brewer which would suggest that those bottles are probably good for 3.5 - 4 volumes of CO2 and that's probably a conservative estimate anyway.


  • NorthernBrewer-AdvancedBottleConditioning.pdf
    88 KB · Views: 0

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