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How Much Does Barometric Pressure Affect Bubble Frequency

I racked a beer into a secondary about a week or so ago. I monitor the frequency of the bubbles with a stopwatch from time to time. Once it hits 3 minutes between bubbles, I usually bottle it. Well, I was down to a bubble every 4 minutes on one batch and could not tend to it that day. The next day, it was bubbling at a rate of once every minute again! :confused: After thinking about it really long and hard, I came to the conclusion that the whole time the beer was in the secondary, we were getting hammered every day by rain. We were under a huge low pressure system. The day I was at a bubble every 4 minutes, was the first nice sunny day we had in over a week. Mile high blue sky. High pressure system. Well, this led me to believe that this was the source of my rapidly changing bubble frequency through my s-trap air lock. Does this make any sense to anyone else? I now use a hydrometer to determine when it's time to bottle and not time.

 uwmgdman 05-26-2006 01:44 PM

Since standard atmospheric pressure (at sea level, most places it will be lower on average due to elevation) is 101325 Pascals (Pa) and extremes on pressure might range from 105000 Pa to 95000 Pa (aside from hurricanes and tornadoes). So a swing to one extreme to standard pressure only accounts for a deviation from average of by 3-6%, or a very small amount. So I would say it's unlikely atmospheric pressure changes will have that much of an impact with bubbling in an airlock.

Now if you've over carbed bottles and they're on the verge of becoming bombs a 3-6% change might be enough to trigger them.

That's my 2 cents...

 david_42 05-26-2006 01:53 PM

If you go from low pressure to high pressure, bubble rate would decrease. More likely there was a slight increase in temperature & yeast activity.

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