Air in?

[redbiers]

First batcher here. Wondering about one thing (well, lots of things but most of my other questions have been addressed in other threads).

The airlock let's the CO2 out but doesn't let air in. Air in being a bad thing. So what about all these hydrometer readings you're supposed to be taking. Isn't there a down side to letting all that air in while you're taking the readings? Or are a few blasts here and there not a big deal at all, even helpful? I'm wondering whether to use the hydrometer at all. The instructions I got with the Northern Brewer kit says that an advantage to using a glass carboy for the primary fermenter is that you don't need the hydrometer. You can just wait till the Krausen falls and the bubbling in the airlock stops.

 

[ShortSnoutBrewing]

By the time you are taking readings a layer of CO2 has formed over your beer more or less "protecting" it for the brief period of time you have the airlock off for.

 

[Funkenjaeger]

You're not going to screw anything up by popping the lid for a minute to take a hydrometer reading. It's continuous oxygen exposure that can be detrimental.

While you can skip hydrometer readings, it's not something I would advise ESPECIALLY for a new brewer. You need to know whether fermentation has really completed before bottling, and until you develop more familiarity with the fermentation process it might take a handful of hydrometer readings on successive days to be sure.

 

[john from dc]

from what i understand, there are (at least) two issues with letting air into the fermenter. one is the potential for oxidation of the top layer of beer, the other is the potential of contaminants entering the beer when it's exposed to the air.

these risks can be mitigated by working quickly and in a clean place. it seems to be generally accepted that the risk of contamination is relatively small, at least small enough that most brewers say to go ahead and sample. i'm able to take samples without moving the fermenter, so i do. i'm not sure if that helps much.

the risk associated with not taking gravity readings is not knowing when your beer is finished. you could mitigate this by leaving the beer in the primary for a relatively long time (a month) but if you intend to bottle or rack to a secondary sooner you're risking killing off the fermentation before the beer is finished.