PET bottle caps loose after 3 weeks

I bottled up a chocolate stout 3 weeks ago in a mix of 14oz and 750ml brown PET bottles. I threw all the bottles into a kitchen cabinet where it stays a nice dark 73F.
Yesterday I grabbed a couple and put them in the fridge. After an hour patiently waiting for the beer to cool, I pulled one out and found the plastic cap was not at all tight on the bottle. Needless to say the beer was pretty flat (though still tasty). I grabbed the other bottle from the fridge and it's cap was also not tight. Sensing a problem, I went through all the bottles in my cabinet. Probably 3/4 of them were loose. I know I tightened all of the caps when I bottled (I even went back and double checked them all after I had problems getting one on straight).

I'm thinking it may be pressure causing the caps to back off on the threads, but I'm not sure. Another problem (maybe related?) is that the 750mL bottles that didn't have loose caps are all bulging. The bottom of the bottles are nearly round and the caps actually have a small dome in the middle! It's only the big bottles that are like this, the smaller ones with good caps seem normal. I racked 5 gallons on top of 2 cups of water boiled with 4.5oz of corn sugar and stirred very well. I'm pretty sure I'm not over primed and it should have been well mixed.

Any thoughts? I'm hoping that there's enough priming sugar left in the bottles to allow them to carb a bit after I re-tightened the caps or is this a lost cause?

Thanks,
Terje

No ideas? Really?

Here's another bit on this. I opened one of the large bottles (750mL) that were bulging. Woo-buddy did it gush! I ended up with almost a pint left by the time the foam stopped. I'm pretty sure it's infected but not positive. Does a gusher infection have a particular taste that goes along with it? This tasted like sucking on a penny or a nine volt. VERY metallic, almost tingley on the tougne and not at all drinkable. It didn't smell bad at all though.

I'm really at a loss here. Hopefully the few bottles I have that weren't loose caps or bulging will be ok.

Terje

I can think of 2 things.

First off, when you opened the gusher, was it warm? Don't ever open a warm carbed beer. Chill it first. I doubt that it's infected. If one of them is infected chances are that they all will be.

Second thing....Is it only the 750ml bottles that are having the problems? Are you sure they are PET bottles that are made to hold carbonated beverages? Are the caps brand new? How much sugar did you prime with and what method did you use?

Stratotankard said:

No ideas? Really?

Here's another bit on this. I opened one of the large bottles (750mL) that were bulging. Woo-buddy did it gush! I ended up with almost a pint left by the time the foam stopped. I'm pretty sure it's infected but not positive. Does a gusher infection have a particular taste that goes along with it? This tasted like sucking on a penny or a nine volt. VERY metallic, almost tingley on the tougne and not at all drinkable. It didn't smell bad at all though.

I'm really at a loss here. Hopefully the few bottles I have that weren't loose caps or bulging will be ok.

Terje

Click to expand...

It sounds like over carbonation judging by the taste (Bitter, tingly, etc). As SILVER13BACK stated, the gush effect could have just been due to the warmness of the beer if it was not properly cooled.

I know you said it stays a constant 73 and dark in the cabinet, but are you sure? I've seen pressure spike during secondary fermentation due to temperature fluctuation (extremely hot day, cooking something in the oven which despite all precautions raises ambient temperature of my kitchen significantly).

I didn't check the charts, but your priming mix sounds about right, as long as it was mixed uniformly before bottling. Hopefully a seasoned brewer will aid, good luck!

The bottles with caps backing off were all 14oz. The ones that are overcarbed were all 750ml Cooper's PET bottles (came with my original kit). The one I opened that gushed was cold from the fridge. The only thing I can think of is that the big bottles were the last ones filled on bottling day. Maybe i didn't get my priming mixture stirred in as well as I thought. I'm still confused about the caps that backed off.

Do you think it's worth opening the big bottles and releasing some of the pressure and then re-capping them? or is they pretty much a loss?

Thanks,
Terje

Let beer go to waste?

BLASPHEMY!

I would try and let them vent and reseal them if I were you. It sounds like they should still carb okay even after doing so. Just do it slow and tighten them back up as soon as they stop hissing to prevent air bacteria. What's another week of letting them sit in your cabinet going to hurt you?

It's a plan then. I'll just vent them and hope for the best. If nothing else I can let them sit for just about as long as needed, I'm not using my PET bottles anymore as I scored a few cases of Sam Adams bottles.

Thanks for all the help guys!

Terje

the metallic off taste concerns me. that's somewhat an indication there's a possible infection. over carbed beer would have a kind of acidic bite to it but would otherwise taste ok.

one potential issue with PET bottles is cleaning and sanitizing. its better plastic than a bucket fermenter is made of, but if it gets a tiny scratch inside from a bottle brush, that scratch will harbor bacteria easily.

what do you use to clean and then to sanitize?

Hi guys,
I am 'fairly' new to home brewing and I'm having a blast... but I have a few questions about these PET Bottles & Caps.
1. Can you reuse the original caps? and if so how many times?
2. When I buy new caps, how do I remove the plastic ring from the original cap?
3. Suggestions for cleaning these bottles? I'm worried about contaminates.
Thanks Guys,
Debbie from Shanty Cellars