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Volcano Beers

For some reason, whenever I brew really dark beers, after a few weeks they get really foamy. If I pour them into a glass, 1/6th of the glass is beer and the rest is foam. Sometimes when I open them they’ll volcano out of the bottle.

I always use 2/3 corn sugar to 2 cups boiling water to make my priming solution.

The beers that I’ve had this happen to are…

NB Black IPA
BB Milk Stout
BB Pumpkin Spice Porter

I’ve made plenty of other beers (not as dark/stout/porter-y as these) that haven’t had anything like this happen.

What am I doing wrong?

Could possibly be the beer did not completely ferment. Residual sugars in the beer and the priming sugars are causing the over carbonation.
What was your OG and FG for the Black IPA? Time in primary? Yeast used and whether or not you made a starter?

Hitchhiking on flars’ response: Did you use a hydrometer or refractometer to ensure fermentation was complete before bottling?

Northern Brewer has a calculator for determining the amount of priming sugar to use. The "always use x oz is usually not a reliable way to carbonate. The most accurate way to carbonate is to use a keg.

Could also be infected.

I would have thought they were infected if it weren’t for the fact that it was all the same type of beer that was having the problem.

I’ve been really bad about using the hydrometer to make sure fermentation has completed. Partially because I figured if I’ve let it sit long enough it should finish. Also, I have no idea what it should finish at.

I’m guessing that the 2/3 corn sugar priming is just not a “good for everything” primer. Looking at the priming calculator on NB, I think I’ll try a little less than 1/2 a cup for my Oatmeal Stout.

2/3 cup corn sugar is not good for everything, but it shouldn’t cause volcanos. Based on your answers, I’d guess the problem is incomplete fermentation and it is just chance that it has happened so far on the dark beers. How long it takes for a beer to be ready to bottle depends on a lot of factors: what yeast you used, how much of it, and how healthy was it when you pitched. What temperature was it pitched at, what temperature was it fermented at, and were there temperature fluctuations during that time. How fermentable was the wort, plus a bunch of other factors that don’t usually matter in a homebrew setting.

Start using the hydrometer to check if it is done. Done means it has stayed at the same reading (whatever that may be) for three days in a row. And if you’re not sure it is ready, give it more time. Delaying bottling for an extra week will never cause the beer to be worse, but rushing it might.

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