I knew Aeration Equipment is a Waste of $...

[dorklord]

If you've ever split a batch and had one carboy where the yeast wasn't viable (you took a chance, even though the starter didn't seem to take off like you had hoped, you used dry yeast past it's prime, you got some of that bad lot of Notty), then added yeast a few days later, you know that it never takes off like the healthy batch that got the yeast pitched right after aeration.

Carry on.

Now, this raises an interesting question.

If aerating with an O2 stone raises the DO level in the wort to a supersaturation level, than that means that Oxygen is going to start coming out of solution. How long does it take for the wort to drop back down to equilibrium?

For that matter, are you going to start to see bubbling from the airlock because of oxygen escaping the supersaturated solution? Could it be that reduced lag times aren't the result of the yeast finishing their reproductive phase sooner, but instead you are simply seeing oxygen coming out of solution instead of CO2?

If I had an O2 stone, I would go home tonight and aerate a carboy full of plain water, and see if I get bubbling from the airlock in the next 24 hours...Actually, I've got a couple O2 tanks for an oxy torch...if I don't have a stone, and say I just make a simple diffuser out of a bit of copper tubing with some holes in it, how long should I aerate for to achieve a good 'oversaturation'?

 

[rayg]

Now, this raises an interesting question.

If aerating with an O2 stone raises the DO level in the wort to a supersaturation level, than that means that Oxygen is going to start coming out of solution. How long does it take for the wort to drop back down to equilibrium?

Not long.
I think the oxygen issue for homebrewers is WAY overstressed. Big breweries
use closed systems, so that for instance after the boil the liquid is pumped
through pipes through the chiller and then into the fermenter, they need to
put some O2 in for optimal yeast fermentation initiation. Once fermentation
begins the O2 not taken up by the yeast is blown out completely by the
CO2 that forms. But homebrewers generally just cool their brew pot in a
sink, or insert a wort chiller into the wort which is exposed to air, so O2 is
absorbed. Transfer to the fermentation vessel involves splashing and even if
done really smoothly, the liquid flowing into the fermentation vessel picks up
O2. As soon as the heat is turned off, the wort begins absorbing 02. So
unless you've got a fancy closed system, you shouldn't have to worry
about it. And if you are adding an actively fermenting slurry to the wort,
instead of dry yeast or a liquid slurry that isn't fermenting, you shouldn't
have to worry about it at all. The initial O2 is necessary to get things
started only.

Ray