# Aerating with O2 questions

I have read people aerate their wort with O2 and a stone for anywhere from 30 seconds to a couple of minutes. Is there a guide online that shows the length of time to run the O2 for either the gravity of the beer or the estimated number of yeast cells in the starter?

What is the “rule of thumb” in second for O2 aerating 5.25 gallons of wort?

I assume the flow rate mentioned when using O2 and a stone is 1 liter of O2 per minute, but since I have no gauge on my valve I can’t set it at 1 LPM for the O2 flow. I have determined that wide open my valve releases 3 liters per minute (inverting a full 3 liter bottle in a tub of water, placing the stone inside the bottle, and running on full open it evacuated all of the water in 1 minute) so if it is common to aerate for say, 60 seconds (at 1 LPM) I would aerate for 20 seconds since I am running at 3 LPM? Did I do my math right?

One liter for anything up to 1.060, 1.5 liters for 1.060-1.090, and two liters for up to 1.120 - these amounts work well for me. I run the O2 at 1L/min and vigorously swirl the wand and stone so there is only a thin layer of bubbles on top of the wort when done - you want to get as much O2 as possible to go into solution.

Wyeast Labs has this info: http://www.wyeastlab.com/hb_oxygenation.cfm

But I think it comes down to your own process. How fast do you pump in the oxygen? How big are the pores on the stone. What’s the wort temperature. The wort gravity. How big is the fermenter head space. Etc.

An oxygen meter would be the only way to know for sure. But for now I would go with the rules of thumb.