My first bottle bomb (bottle conditioning with honey)

[milleniarist]

I've been homebrewing for more than four years, almost always conditioning in the bottle with priming sugar and yesterday I had my first bottle exploding. I went through my notes several times and I have no clue how this could happen.

Here are some details:

• The beer was a saison fermented with a blend of the Dupont and Thiriez strains.
• OG: 1.036 - 21 IBUs
  
• 90% Pils - 10% Unmalted Wheat
  
• Brett C and 10.2 oz of honey added 4 days after pitching the Saccharomyces.
• I bottled after 72 days of room temperature fermentation and gravity was 0.9985 (yes, my hydrometer reads up to 4 decimal points, that's how anal I am when dealing with diastaticus strains).
• Since it was so low I decided to risk it a bit and aimed for 3.4 CO2 volumes.
• For 6.87 gal (26L) I used 4.58 oz (130g) of table sugar and 6.24 oz (177g) of honey.
• I measured the honey to have 33.7 ppg extract.
• The honey was diluted in hot water (not boiled) and stirred thoroughly in the bottling bucket.

Only 6 days after bottling, one of the 75cl champagne bottles exploded. After cleaning the mess I opened another one, de-gased the beer and measured its gravity. It was 0.9981, slightly under bottling gravity but not enough to break a bottle. Those 0.0004 extra would have got it up to 3.6 Vols and I think champagne bottles should withstand at least 4 if not more.

One of my theories is that during the first days inside the bottle the yeast is releasing CO2 to the bottle's headspace faster than the beer is able to absorb it and that makes the pressure inside the bottle higher until it reaches equilibrium. Does that make any sense to anybody?

I am waiting to see what happens with the rest of the bottles. So far no other explosion.

 

[Miraculix]

I think you just had a bottle with more sugar due to mixing failure when throwing the sugar and honey water in. Or the bottle had a mini crack.

 

[RPh_Guy]

+1
Most likely the honey did not fully dissolve and some bottles got more than others. It's not easy to dissolve honey!

Another possibility is that just one bottle was stressed or had a defect. Champagne bottles can generally hold a lot of pressure (as I'm sure you know), so one failing may indicate an issue with the bottle rather than the bottling process.

One of my theories is that during the first days inside the bottle the yeast is releasing CO2 to the bottle's headspace faster than the beer is able to absorb it and that makes the pressure inside the bottle higher until it reaches equilibrium. Does that make any sense to anybody?

No, CO2 is released directly into the liquid, already dissolved. That's where the yeast are.

• For 6.87 gal (26L) I used 4.58 oz (130g) of table sugar and 6.24 oz (177g) of honey.

• I measured the honey to have 33.7 ppg extract.

The math checks out fine.

 

[bucketnative]

You are ignoring the possibility of a mechanical fault in the bottle itself.

Running through the math you should have been close to 3.0 vol, with a total of 4 points added to the beer. Each point is approx. 0.5 vol of CO2 added to the beer, which already contains CO2 in solution.

Sugar: 0.29 lb * 46 ppg / 6.87 gal = 1.95 points

Honey: 0.39 lb * 37 ppg / 6.87 gal = 2.10 points

You used about 50 % of the required sugar and 50 % of the honey called for by Northern Brewer's calculator.

 

[Vale71]

One of my theories is that during the first days inside the bottle the yeast is releasing CO2 to the bottle's headspace faster than the beer is able to absorb it and that makes the pressure inside the bottle higher until it reaches equilibrium. Does that make any sense to anybody?

You just described what happens normally during bottle conditioning. As refermentation progresses enough CO2 is released to the headspace to constantly mantain equilibrium with the ever increasing carbonation. There is however no way this is going to cause the headspace pressure to suddenly spike, it will always follow a more or less steady curve matching the progress of refermentation.

In your case I would suspect either a faulty bottle or uneven distribution of the priming sugar(s) as the most likely culprit(s).

 

[RPh_Guy]

Honey: 0.39 lb * 37 ppg / 6.87 gal = 2.10

He measured the honey as 34ppg but you're right it would be lower than 3.4 vol CO2.

 

[milleniarist]

Faulty bottle could be one possibility, that's why I'm not dumping the whole batch yet.

You just described what happens normally during bottle conditioning.

I think I did not explain my theory clear enough. Another way to put it would be: is the CO2 produced by the refermentation going to the headspace and then re-absorbed by the liquid or is it being produced already dissolved into the beer like RPh Guy claims? Either way, equilibrium between the two mediums does not happen instantly and before that occurs the pressure in one of them will be higher than in the other. This is just guessing though, I might be wrong in my assumption.

 

[Vale71]

CO2 is released into the liquid and diffuses constantly both through the liquid and through the surface into the headspace. Since bottle fermentation is quite a slow process any momentary deviation from equilibrium due to diffusion speed will be in the order of a few millibar at best and always with a minus sign, that is to say headspace pressure will lag slightly behind (i.e. be lower than) what the tables say is the equilibrium pressure for the current carbonation level.
I think you just need to whip out Occam's razor and accept that it was most likely a faulty bottle or non-uniform mixing of beer and priming solution.

 

[MikeCo]

I had a batch of Belgian Golden Strong Ale once where only one bottle exploded. I don't know why for sure, but I remember some of those bottles being dirtier than normal since they were given to me. It's possible the bomb bottle had some wild yeast or bacteria in it that caused it to explode.