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First time using pure o2

Sunday was my first time using my new o2 kit from Williams Brewing. As always when using dry yeast I re-hydrated the USO5 prior to pitching. I hit the carboy with a 45 second shot of O2 and then pitched my yeast. The next day the top of the wort was a sheet of glass and no activity at all. I figured that I must have somehow killed my yeast so I pitched a second pack of yeast without re-hydrating it. Activity started in less than an hour. The brew has been churning away ever since.
My question is, could the second pack of yeast taken off that fast or did the first pack finally kick in?

Could have been either. When you rehydrated, did you see any sign of activity? That will tell you if the first pack was DOA. All it takes is a particularly hot day in the sun to do that to a yeast pack, or bad storage conditions before it even got to you. I’ve had a few dry yeast packs that were non-viable when I got them.

First pack had a nice cream to it when I re-hydrated. Do you use pure o2 with dry yeast?

By “nice cream” do you mean it looked active and was forming some bubble activity? That would mean it was viable.

I’ve never used O2 injection, but all the literature says it gives the yeast a better shot at the initial stage of reproduction that happens when you first pitch them, as long as you don’t oversaturate it. I’m not sure if dry yeast would be any different in that regards, though I am pretty sure that due to the way they are prepped for the drying process they have less need of it to perform a good fermentation. I hope you didn’t give O2 directly to the yeast when you were rehydrating them - pure O2 is poisonous in high concentrations.

From what I understand, dry yeast doesn’t need to be aerated. Pure O2 might be detrimental to it.

You don’t really need to aerate or oxygenate when using dried yeast.

See about halfway down the page:

That said, I doubt a 45 second shot of pure O2 did any damage.

Using a disposable red oxygen tank (the kind you get from a hardware store) on a very low setting, I routinely give medium gravity wort a 60 second shot of O2 before pitching yeast (90 seconds for high gravity wort) with great results.

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