[jaybeerman]

I disagree, Drew.  The purpose of the video is to promote what we all know is a poor brewing practice...making a starter with dry yeast.  I've emailed the powers that be asking them to remove it.  Cranky?  Perhaps. 

Yeah, but the guy is quite fashionable, nicely dressed (did you not see the goggles?), and there's a catchy soundtrack; surely you can forgive a little misinformation 

[weithman5]

.  not necessary with dry yeast to make a

would you split up the dry yeast? I'm considering a scale that could do that kind of measurement anyway.

we'll see how it works.  i just brewed (i brew 1 gallonish batches)  used about 1/3 of the package, then 1/3 in a cider (again 1gal)  the remaining 1/3 i am going to make a starter from and then save this starter as a slurry for the next few batches (probably divide again and make a few batches)

[punatic]

Old laboratory adage:

"A watched flask never boils."

[euge]

Old laboratory adage:

"A watched flask never boils-over."

There. Fixed it for ya!

[punatic]

It's gotta boil before it will boil-over.

[gimmeales]

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!

[bluesman]

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.

[punatic]

Is there a problem with using an airlock on a yeast starter?

[tschmidlin]

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.

[punatic]

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.

[tschmidlin]

Yeah you'd think so, but the O2 flows because of the O2 gradient.  Weird eh?

[hopfenundmalz]

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.

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.

[punatic]

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.

[majorvices]

Regardless of whether or not o2 can get in under the foil, only wankers use airlocks on starters. Know that. 

[narvin]

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.

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.