What possible reasons cause a (pale) beer to fail to carbonate in the bottle

Question

Max Colledge

2021年10月18日 13:35

tl;dr:

Almost half of my pale beers have trouble carbonating in the bottle, being almost uncarbonated after 2 weeks

I don't think I have ever had this issue with a dark ale or porter.

I've been brewing for the better part of a year now, doing a weekly small batch brew. I've been brewing a mix of pale and darker ales/ porters.

All of my beers use some protafloc for clarity
All of my beers use some Clarity Ferm (to make them gluten free)
All of my beers have 4 weeks in the fermenter (5L glass demijohn), even if the bubbler airlock flattens out before this
All of my beers spend 2 weeks carbonating in the bottle in a dark cupboard, using 1 coopers carbonation drop per bottle
All of my beers come in around 4-6% abv
I use a mix of yeasts in different beers, lately most of my pale beers use lalbrew verdant ipa
I live in the UK (if you're wondering about temperature)

I'd be happy to clarify any questions

Category Mac

Frank van Wensveen · Accepted Answer · 2021年10月18日 13:35

Possible causes of uncarbonated beer after bottle conditioning:

Insufficient priming sugar in the bottle, or no carbonation drop in the bottle. (I've made that mistake myself occasionally, thinking that I did put one in but didn't). If half your bottles are effected, I think we can rule that one out.
Insufficient yeast left in the beer or insufficient yeast viability. Depending on how much yeast you settle out or how vigorous the yeast still is after fermentation you may run into problems with some bottles depending on the amount of dissolve oxygen in the bottle, which may vary. If this is the case, the uncarbonated beers will taste a lot more sugary-sweet than the carbonated ones.
Leaky caps, which allow the pressure to escape.
Low temperature. If the bottles condition at the low end of what the yeast will take, in-bottle fermentation may or may not take off.

And that's pretty much it, really. Not much else can go wrong. So it's almost certainly one of these factors.