[bluesman]

The ROT I'm familiar with is that you can aerate up to 14 hours after the first signs of fermentation.

+1

Presumably only during the growth phase.

[seajellie]

Thanks for the info guys, I'll give my next bigger beer (a Belgian ale) a bit more aeration like this.

The good thing about experimenting with Belgians, ya' can always just claim that "it's character, not a mistake."

[yugamrap]

I get such good aeration out of my cheap'n'easy Mixstir that I've never considered a more expensive/complicated method.

+1  I use my Mix-Stir as I run the wort to the fermenting bucket from the kettle.

[beercheer4me]

I am new and been reading alot on this forum ,,,,
I got a wine de-gaser  stir stix on a drill for 20 seconds
I guess it works, 

[jjflash]

Everyone always tells posters to aerate enough. So how much O2 is enough without using too much :?:

Per "Handbook of Brewing", 1ppm per degree Plato is the professional industry standard.
Impossible to measure this without a high quality oxygen saturation meter.
When people give you the advice for "X" minutes they are taking a wild guess.
Oxygen / yeast pitching rate are intimately correlated.
Some suggest underpitch and over oxygenate.
Others overpitch and under oxygenate.
It is always a balancing act.
Luckily, normal gravity worts are very forgiving of mistakes with oxygen.

[tygo]

Luckily, normal gravity worts are very forgiving of mistakes with oxygen.

What about very high gravity worts?  Planning on doing a 1.118 brew soon and have been debating how much oxygen to hit it with.  In my mental debate I think I'm currently at 30 seconds of pure O2 and then shake the hell out of it.

[dhacker]

Well . . there are those of the mind set that you can knock the oxygen OUT of solution by churning the wort too much after oxygenation. I know some individuals (specifically making starters on stir plates) that give the wort a blast of O2 and let it sit for several hours before spooling up the stir bar.

[cojeep636]

I just thought i'd input, im relatively new to brewing, but thought i'd share some information from other sources that i've found.
I have a couple aquariums, and always thought that putting bubbles of air into the water would aid in the oxygen level in the water, but come to find out its a VERY minimal effect in comparison to circulating the top surface of liquid (in our case,  beer).

The idea is that the surface area of a group of bubbles is very little when compared to the top surface area of an aquarium, or again, in our case, a fermenter. The oxygen absorption, thus, takes place mostly on the top surface. So hopefully this can shine some light on the most effective methods of oxygenation.

[jjflash]

What about very high gravity worts? 

I would tag that one super high gravity wort.
Most unforgiving of mistakes.
When I brew that big I shoot for 18 - 20 ppm oxygen.
Remember it is a balancing act with yeast pitching rate.
I shoot for 0.75 - 1 million cells per degree Plato per milliliter on super high gravity wort.
Hit it with oxygen and let it sit quiet - oxygen easily comes out of solution.
Yeast propagate while oxygen is still present.
Yeast ferment when oxygen is depleted.

[tygo]

Ok, so no shaking and 1 min of bubbling O2 through the wort it is.

[Kaiser]

Yeast propagate while oxygen is still present.

They'll actually keep growing even once the oxygen is gone. What is happening is that the yeast is using the oxygen to build up their sterol reserves. These sterol reserves are depleted when the yeast is growing since in the absence of oxygen both the mother and the daughter cell get half. At some point growth will stop when the sterols in the yeasts are too low for further growth. But that happens quite a while after all the oxygen is consumed. High gravity fermentations need more O2 that regular fermentations since you don't want the yeast to deplete their sterol reserves too much. If that happens the cell walls get too weak to withstand the rather extreme alcohol concentrations.

In the presence of a lot of sugar, and any practical brewing wort has lots of sugar from the yeast's point of view, vey little to none of the oxygen is used metabolize sugars aerobically. Even in the presence of oxygen the yeast will ferment. This is called the Crabtree effect.

Kai