Yeast washing and removing oxygen

[CalmYourself]

In the yeast washing sticky Bernie Brewer says

Boil it for about 20 minutes or so. This will sanitize everything as well as get rid of any oxygen in the water, so the yeasties will take a nice long nap.

I've always been a little confused by the logic of removing oxygen, so maybe someone can crack an egg of knowledge on me here...

Fact: The amount of dissolved gas in a liquid is a function of the temperature of the liquid
Fact: The higher the temperature of the liquid, the less the amount of dissolved gas
Fact: The water will still be in contact with the atmosphere post boiling while cooling (the gas in the jar will contain air, fresh air again when you open the mason jar)
Fact: The air in above will probably contain oxygen
Fact: As water cools from boiling, it will begin to re-absorb the gasses in the atmosphere around it in accordance with Henry's gas law
Fact: When you wash yeast by pouring the now cooled boiled water into your fermenter, the splashing will cause agitation
Fact: Agitation increases dissolved gas pickup

Maybe I'm being a bit dumb here, but based on this the only way I can see to ensure oxygen doesn't re-enter the water is to do the cooling either under a vacuum or in an airtight CO2 filled vessel, and also by then purging the fermenter and all other transfer vessels of all oxygen before mixing in the water again.

So my question is: Surely by the time the water has cooled it's reached normal atmospheres worth of dissolved oxygen levels again? And again by further agitating the mix when pouring the water onto the yeast cake?

 

[medusa1066]

You are probably not too far off that those manipulations will reintroduce some oxygen. But, like in many cases of brewing, you are trying your best to control your system. Unless you have empirical data showing how much oxygen is introduced with splashing/sitting on a counter, you really don't know how saturated the water is with oxygen. Remember that air is mostly nitrogen. RDWHAHB!