Sooooo close! If only he’d used a smack pack or tube of yeast I think most of us would forgive the airlock faux pas. I’m on the fence - agree with Drew’s point because of the production quality (and the process will produce fine beer), but Denny makes a point that resonates with me (because he’s right about established best-practices)
There’s only one place this will be resolved - THE OCTAGON!
p.s I also agree that table rules!
Well done!
…again I’ll reiterate…except for the dry yeast and air-lock. I also don’t think it’s necessary to sanitize the flask prior to boiling as the boiling process will properly sanitize the flask.
Is there a problem with using an airlock on a yeast starter?
Not a problem per se, but it will inhibit yeast growth. You want some air flow in to get some extra O2 for the yeast to build cell walls. Foil or a foam stopper is good enough to allow air flow while keeping out bugs and dust.
Dang, I’ve been doin it wrong for 22 years. How much of an air exchange do you suppose you get through a foil cap or foam stopper?
Positive pressure created by the generation of a heavier than air gas in a confined space, I think it’s a one way flow - CO2 pushing outward.
Yeah you’d think so, but the O2 flows because of the O2 gradient. Weird eh? 
Partial pressure is what you have to think about. The O2 will go in due to the higher partial pressure of O2 on the outside like Tom says. Sierra Nevada went away from the twistoffs to the O2 barrier caps. The beer was not going flat, but O2 was getting in past the seal. Counterintuitive.
I’m guessing that the model for this idea is the same as the one for how bottles of crown-capped beer becomes oxidized over time?
Ah, it is. hopfenundmalz posted while I was writing this.
I think that model is incorrect because it is based on a static interface between the confined space in the container and the atmosphere. The interface between the starter’s confined space and the atmosphere is dynamic due to the generation of CO2 by fermentation.
Picture the O2 molecules as salmon trying to swim upstream against the current in a river of CO2.
Regardless of whether or not o2 can get in under the foil, only wankers use airlocks on starters. Know that. 
That’s why you shake it every time you walk by, or use a stir plate. The agitation is going to get some O2 in there.
Thank you for sharing your thoughtful insight.
Yours Truly,
WankingAwayInPuna. ;)
Dear Mr. Wanker,
I want to thank you for your avid participation in the AHA Forum. I hope it has been a learning and inspirational experience. We appreciate your active engagement and hope you will continue to join us ongoing. By the way, using foil to cap your yeast starters is recommended. Please don’t hesitate to contact us for all of your wanking needs at your convenience.
Cheers ;D
Well, the AHA removed the link to the video from our site as I requested. I agree the production values were good, but speaking as someone who’s spent over 30 years in the production biz, if the content isn’t accurate, all you’re left with is a good looking nothing.
You might be right to some extent, but the flow is pretty slow and there is likely to be O2 molecules with sufficient energy to overcome the current, especially when the flow is spread out over the mouth of the flask instead of concentrated in the outlet of an airlock. I don’t have any data to support this though, maybe someone else does.
I was talking to Dana, aka the man with the goggles, the other day about the video. It was not their intent to recommend making a starter for dry yeast, only to demonstrate how one goes about making a starter. Their choose of dry yeast was purely economics, $3 for dry and $8 for liquid. They felt Home Brewers advanced enough to consider making starters would know that dry yeast doesn’t require, nor should it utilize, a starter.
Alas, they made assumptions and that is never a good thing but their intent was good and I still like the video. I wouldn’t hesitate to recommend it but I would qualify it with “Use liquid yeast only, dry doesn’t need a starter” and “Use foil or foam, not an air lock, your yeast will be happier”
The genuine desire to help newbie brewers was clearly apparent in the video. Is there opportunity to remake the video? (Assuming Dana and crew feel up to it) Perhaps the video could be broken into two portions; reconstituting dry yeast and making a starter for liquid yeast. As far as the next version goes; Bluesman made a good point, sanitizing before a boil isn’t necessary. Skip the airlock. Technical stuff - once the boil is started you can loosely place the foil over the mouth of the flask, as the steam rises it will sanitize the foil as well. When the starter is ready for yeast, it’s not a bad habit to hold the foil above the mouth of the flask. This accomplishes two things, it shields the mouth of the flask and it keeps you from setting the foil on a non sanitized surface. Good luck with the second version. cheers, j