Caps on PET bottles are bulging!!

[baxtefer]

Should I be scared that some of the caps on my PET bottles are bulging??

I brewed a Hefeweizen on June 20th (OG: 1.045), fermented for 2 weeks at ~70F and bottled into 500mL PET bottles on July 3rd (FG: 1.008).

Primed with ~1 cup dextrose, dissolved in 2 cups boiled water (6 Gallon Batch). Dumped into the bottom of the bottling bucket and racked on top.
Bottles were brand new and sanitized with OneStep.
I sampled a few after 2 weeks in the bottle at ~70F and 24 hours in the fridge. Tasted ok (if only a bit watery and lacking mouthfeel), seemed properly carbed.
Fast forward 2 more weeks. I come back from vacation to see that the caps on a couple, but not all, of the bottles are bulging. Some have a distinct domed shape, while others are still pretty flat?
Other than the caps, the bottles seem fine. just rock-hard.

Should I be concerned? And more importantly, what might be the cause?
- too much priming sugar?
- priming sugar not mixed properly?
- bottle conditioning too hot? (The cupboard they've been in for the past 2 weeks may have hit 85F for an extended period of time)
- infection?

I have one of the bulging-capped bottles in the fridge right now. I'll give it a couple of days before opening it, carefully, in the sink. I'm expecting a gusher.

 

[goodbyebluesky82]

Based on that amount of corn sugar, theres really no way all of them could be bulging unless it had not reach FG before bottling, i.e. not done fermenting yet.

Since you say it is only a few of the bottles bulging, then it is highly probable that the sugar was not mixed thouroughly enough and some of the bottle got a bit too much fermentables, and are thus creating more C02 than they should have.

Its really based on amount of fermentables available rather than any variables like temp, etc.

I would open them and drink 'em, or at least bleed off some pressure since they have twist off plastic tops. At the least, put them somewhere they won't do damage to anything if they do blow up. Those rubbermaid storage containers work nicely. Putting them in the fridge may halt the fermentation enough to keep them from exploding but it is still a slight risk.

 

[ksbrain]

I wonder if a PET bottle could blow up... I always thought that to be one of the benefits of plastic over glass.

 

[SweetSounds]

I wonder if a PET bottle could blow up... I always thought that to be one of the benefits of plastic over glass.

Draino bomb anyone?
Not that you'll reach that pressure with CO2 in beer (I don't know how much it takes to blow one) - But if one did get that high, it's a devastating reaction. It'll swell to the size of a basketball and go with enough force to take off a hand.