exploding bottles - 1st time in 20 years of brewing

[RobboMC]

As the heading says, I've been brewing for 20 years, started with dump and stir kits
and now brew about 50/50 grain and extract. I've been bulk priming for a decade or more.

Last Xmas I bottled a Dark Ale and extract beer ( my kids bought it for Father's Day so I had to brew it up )
and about 8-10 weeks after bottling the bottles started exploding.

Luckily I managed to open all the 330 ml bottles into a bucket, most were like fire extinguishers when opened,
such was the excess carbonation. The beer that I did get to drink ( before the bombs went off ) was excellent given the ingredients.

The OG was 1075, at Day 9 the gravity was 1031; bottled on Day 20 at 1029. Bulk primed with 6 g/l of dextrose powder.

Now, 8 month later, my lady has given me an ultimatum, brew decent beer or she's leaving!

So I am brewing again.

The burning question remains, what went wrong??

I don't usually use this much dry malt,
I did go through a period of years using Coopers Brew Enhancers

Any ideas to guide me, for now it's back to basics and make no mistakes.


The dark ale recipe looked like this:

Coopers Dark Ale kit
1 kg Country Brewer Dry dark malt
1 kg Country BrewerAmber Brew Booster package
1.5 kg Dark Crystal/ Brown grain, held at 65 deg C for 45 min, then boiled
with 60g of Fuggles hops for 10-12 min

 

[philrob]

I don't know which nor how much yeast you used, but to have a drop from 1.075 to 1.031 is an Apparent Attenuation of only about 59%, which seems vey low to me.
This leads me to guess you probably underpitched and the yeast slowed down before fully fermenting to its potential.
Your FG of 1.031 is much higher than anything I've ever bottled at.
If, as you say, it tastes OK, then it's probably not infected, which could be another source of gushers and bottle bombs.

The answer is to pitch plenty of yeast, and give it time to do its job. Good luck.

 

[RobboMC]

Yeast was

Empire Ale M15, wouldv been a single sachet

 

[Paleman]

1031. You just shouldnt bottle at that reading. Obviously a stuck fermentation.

 

[philrob]

1 sachet of yeast for that gravity in a regular sized batch is definitely underpitching.

 

[Drubbing]

The burning question remains, what went wrong??

Not enough yeast. You used 2kg of extra fermentables, plus the Dark Ale kit, and that will produce a high OG. Two packets of yeast would be needed.

High ABV brews needs more yeast, otherwise they will not ferment out fully. That brew was not finished at 1031. After bottling and introducing more sugar, you started fermentation again = bombs.

 

[RobboMC]

Thanks for all the responses. By the way the brew was 1029 when bottled but that
doesn't change things much.

I've pulled out my old records, to see exactly how this one compared.
My annual big black beers ( see the photo ) usually have lots of unfermentables
but the attenuation has been between 67 and 70%, except once I bottled
at 62% and 1031. That brew had lager yeast and must have stayed cool enough
in storage to keep the continuing fermentation down. I may have been walking this fine
line for some time! This one ended up in the storage fridge ( 20 deg C ) during February so
probably got nice and warm.

Clearly 62% is too low and I was over confident and not careful enough having
brewed successfully for so long. There's a lesson there somewhere.

As to the amount of yeast, I have brewed big ales with 2 kits and 2 kilos plus a bit of grain
using only one sachet of either Safale or Saflager many many times. Shows how good this yeast is.
This batch of bombs was not Saf yeast. I may start yeast farming.

For this new batch I've just used 2 sachets as you guys suggest and I won't be bottling
at 62% ever again.