From: jdecarlo@mitre.org (John DeCarlo)
Subject: Re: Aeration of wort?
Summary: Does it really happen?
Organization: MITRE Corporation, McLean  VA
Date: Wed, 16 Dec 1992 13:46:56 GMT

In article <1992Dec15.171346.10670@minnow.sp.unisys.com>
 ralph@minnow.sp.unisys.com (Ralph Smith) writes:

>Somebody writes:
>>I have heard alot of talk on this newsgroup lately about improper aeration
>>of the wort being the cause of stuck fermentations.  

>I have been wondering about this aeration thing for some time now.
>A few years ago, I was setting up a marine aquarium and the general
>feeling at that time was that the bubblers in a tank provide virtually
>no aeration of significance, and that the bulk of the aeration effect was
>at the water/air interface on the surface of the tank.

This is probably true for fish tanks, since they tend to have a wide, flat 
surface exposed to the air 24 hours a day.  Compare the surface area of the 
bubble from your bubbler and the amount of time involved, and I suspect that 
there is less surface exposed to air per minute from the bubbler than there 
is per minute at the surface.

As far as I can tell, this is pretty irrelevant to the discussion about 
aerating wort, though.

>So, my question is:
>Whats all this about shaking and stirring your wort? According to the
>aquarists(?) we're just fooling ourselves.
>Is the real benefit just the mixing action with the yeast, exposing it   
>to all that good wort faster?
>Or - are the aquarium folks all wet?

I'm probably dense, now that I am over 30, but what made you leap from the 
comparison in a fish tank to the discussion of wort in a carboy?  Is there 
any similarity in geometry or methodology?

If you want to argue about this (and I do), then it seems to me that shaking 
your carboy could *at best* simply get all the oxygen in the air in the 
carboy dissolved in the wort.  How much, though, do you normally have there?

Sure, in my 6.5 gallon carboy, there should be about 1.5 gallons of air 
after pouring in 5 gallons of cooled wort.  Is that enough?  Probably.  If 
you are using a 5 gallon carboy with a blow-off tube, how much benefit could 
you get by shaking the carboy?  Relatively little, it seems to me.

So, how do *I* aerate?

I splash the wort going into the carboy, enough so that it foams up nicely.  
Presumably this mixes in as much air as can easily dissolve in the ten 
minutes it takes to slowly, splashingly fill the carboy.

What about recent articles and talks about aerating with bubblers?  Reports 
are that it works fantastically, especially using the 5 micron (do I have 
that number and unit right?) bubblers (which are essentially sterile, 
filtering out bacteria and such, if I remember correctly).  Could this be 
because of the increased surface area per volume of air, due to very tiny 
bubble size?  Could it be because transfer at the surface of a stable liquid 
occurs slowly?  Could it be because these systems often use oxygen instead 
of air and that works much more quickly?

I don't know.

Anyway, consider all these factors and any others not mentioned but relevant 
when you decide how to aerate your wort after it has cooled and the yeast 
are either pitched or just about to be.  

But *please* aerate your wort at that time.  I will thank you, you will 
thank you, and especially your yeast will thank you.

John DeCarlo, MITRE Corporation, McLean, VA--My views are my own
Fidonet:  1:109/131  Internet:  jdecarlo@mitre.org
Newsgroups: rec.crafts.brewing