Why did I get bottle bombs?

[html034]

I just bottled a batch of porter on Monday, and tonight the top blew off of one of the bottles. Upon further inspection, this is the second blown bottle in the batch.

Let me briefly recount vital information:

Fermentation time and temperature: 64F for 3 weeks (airlock activity done after 2 or 3 days).
Final Gravity: ~1.014
Priming sugar: 5 oz of table sugar (boiled with 16oz of water, racked beer on top)
Bottling temperature: 82F (fermented in a cold basement, brought fermenter upstairs to this ambient temp, let sit for a day before bottling).

I am trying to figure this out, and here are my suspected causes:

-insufficient mixing of priming sugar during transfer
-CO2 Off gassing due to higher ambient temperatures (the bottles have been sitting at the same low 80s temperature that they were filled at).

Does anybody have an idea of what might be happening here?

Should I move the bottles back to the basement? Should I even touch them? Should I try opening one to see what sort of pressure there is?

Any thoughts or suggestions are appreciated.

 

[PeteNMA]

Did you stir the priming solution into the beer? If not then that's likely the issue. You can stir the whole shebang in the bottling bucket using a nice long sanitised spoon.

The one time I skipped doing this I had about a dozen bottles of one batch explode while the rest were undercarbed. I suspect that if you rack the beer gently into the sugar solution then you don't get a good kiz

 

[html034]

Did you stir the priming solution into the beer? If not then that's likely the issue. You can stir the whole shebang in the bottling bucket using a nice long sanitised spoon.

The one time I skipped doing this I had about a dozen bottles of one batch explode while the rest were undercarbed. I suspect that if you rack the beer gently into the sugar solution then you don't get a good kiz

I didn't stir it, but then again, I have bottled at least 2 dozen batches without ever stirring, and this is my first bottle bomb situation. This may well be the issue, but if so, I am baffled that this is the first time it's happened.

 

[duboman]

Bottle bombs occur because:

1. Too much priming sugar
2. Incomplete fermentation of beer
3. Infection

Did you bottle a full 5 gallons of beer?
Did you verify the FG over a few days?
Did you weigh out the sugar or measure by volume?
Did you taste the beer to make sure it's not infected?
The temperature you use is the temp that the beer sat at the longest, not at what you bottled it at. The colder the beer the more CO2 there is present so if you fermented at 65 for example and bottled at 75 you would use the 65 which would mean less sugar was needed.