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I've just finished a brew session today and decided to verify my manual aeration technique for cooled wort with oxygen measurements. I thought I was getting some aeration while stirring vigorously during cooling with my immersion chiller once the wort was below 40ºC. However, readings indicate I'm only at 0.5 mg/L dissolved O2. I then usually try to splash the wort as I'm transferring from the kettle to the fermentor by shaking the heck out of the carboy while it's siphoning, and according to my oxygen meter I gained nothing, still at 0.5 mg/L. It could be my meter not being able to read in chocolate sludge (made a Chocolate Hazelnut Robust Porter - I have 4 inches of chocolate sludge now settled out in the bottom of my fermentor), so I thought I'd check with you all on how you aerate your wort.

I'm thinking I'd like to get some equipment to either bubble oxygen or air next time I brew and see if I can improve my oxygen concentrations and shorten my lag times. My starters should be adequate, I use a stirplate and follow pitching rates from Mr. Malty's yeast pitching calculator, so I suspect it's my aeration that could be improved.

How do other's aerate their wort and how are your lag times? Anyone else measure their oxygen concentrations post aeration?

I've often thought about measuring the DO, but never got around to it. I have an O2 injection system with a scintered ss stone for my high gravity beers (1.060 and up), but under that I am happy with big starters and shaking the hell out of the wort in my 6.5 gallon carboys. I like the info from wYeast, and generally assume that by shaking I am getting the maximum 8 ppm:

http://www.wyeastlab.com/faqs.cfm?website=2#r42
http://www.wyeastlab.com/hb_oxygenation.cfm

My lag times are easily 12 hours before visual fermentation on average beers with liquid yeast starters (I use Mr Malty as well). Repitched I usually get much quicker reaction - probably from really high pitch rates.

I was going through the same thing and spent the $60 on the Oxygenator from Liquid Bread. It works like a charm and uses the disposable oxygen cylinders you can pick up anywhere.
My typical lag time is right around 6 hours but keep in mind I always use a starter, cultivated on my stir plate, usually around 1.25-1.5 litre range. I also try to go by the Mr. Malty pitch rate calculator.

Forgot to say that although I would like to, I have never measured my DO levels.

Thanks guys. I have read those links as well. Seems the oxygen was adequate since it was less than 8 hrs for signs of fermentation. So, either 0.5 mg/L of oxygen is enough (doubt it) or my oxygen sensor doesn't work in chocolate sludge laden wort. I'll have to try it again with a lighter wort.

I didn't realise you could get disposable oxygen cylinders. I think I'll try that setup and see if it improves my fermentations.