We have found that after our beer has been bottled for several months that it has a very large head on it when we pour. It doesn't matter how slow we pour or how angled the glass is - it foams up like crazy. Are we doing something wrong or does this happen often with natural carbonation?
Have these bottles been in the fridge for at least a few days to force the CO2 into the beer? If not try that. Otherwise the beer is either well over carbonated
So over or under carbonating will cause gushers? I just can't wrap my head around that logic. My flat beer doesn't ever gush. Where does the chill for two days to force co2 into the beer come from?
Also I have had beerstone at the homebrew level.
Can't comment on the Beerstones but regarding the CO2, yes, as we know there are different levels of CO2 in the beer dependent upon temperature of the beer. Colder beer will retain higher levels of CO2 than warmer beer. This is why, when priming, it is important to factor beer temp for the sugar calculation. When you take a bottle of beer that has been conditioning at 70+ for a few weeks and then open it warm there is the possibility that the bottle will gush because the CO2 has not been full absorbed into the beer (it may happen, it may not). If the beer is then refrigerated for a few days the beer will absorb the CO2 more readily and stabilize in the beer.
This is all my understanding as relayed over the years by people more knowledgeable than I. I only bottle and always have and these are also my experiences.