Open flask when agitating yeast starter?

[Gerry Nobody]

Title is basically my (probably stupid) question. I am making a yeast starter for the fist time and don't have a stir plate so just agitating occasionally throughout the day. Do I need to take off the tin foil cover when doing this to let some air in?

 

[bailey mountain brewer]

Nope.

 

[RM-MN]

People will tell you that you need to add oxygen for the yeast to reproduce but when your starter is in a flask there will be little oxygen to add when you swirl it as the activity of the yeast will have displaced that with it production of CO2. Swirling it mostly removes some of the excess CO2 and keeps the yeast in suspension.

 

[Gerry Nobody]

Thanks!

 

[RM-MN]

Be prepared for a beer volcano when you swirl that erlenmeyer flask. Sometimes the CO2 wants to come out all at once. Doing the swirl over the sink may be the best.

 

[passedpawn]

What you DON'T want to do is use a airlock in an Erlenmeyer flask when growing yeast. I knew this one idiot (ahem) that did that for a while.

 

[IslandLizard]

Be prepared for a beer volcano when you swirl that erlenmeyer flask. Sometimes the CO2 wants to come out all at once. Doing the swirl over the sink may be the best.

As long as you swirl often the volcano won't happen or not as violently.

Foam-overs or blow-offs usually happen when you're at work, or overnight, when asleep. When that happens you stand to lose as much as half the starter to the countertop. It's messy and such a waste of good yeast.

Therefore, ask your family members to give the jar, jug, or flask a swirl whenever they walk by.