Covering your starter while cooling it

[Gustatorian]

I cool my erlenmeyer in a bath of ice water over 10 minutes or so...but I never cover it while cooling. Does anyone cover it with foil or anything? Is there any benefit?

 

[Yeastieboy]

Sanitized foil. Absolutely. The moment it drops below 212F it is susceptible to wild yeast and bacteria in the air. Everything's debatable but this is so easy, why wouldn't you?

 

[TheHopfather]

Covering with foil is just added insurance against anything falling into the flask. You wouldn't want your starter wort to get contaminated. Whether it is necessary is debatable, but it sure couldn't hurt.

 

[day_trippr]

Covering with foil is just added insurance against anything falling into the flask.[...]

True - like splashed cooling water.

The foil is not going to keep airborne bugs out, however. If there's head space in the flask, when it cools it's going to pull air in, along with whatever's riding along.
Generally it's a good idea to do yeast ranching in an area that is "quiet" wrt airflow and not obviously susceptible to contamination. Don't put a starter together right in front of an open kitchen counter window, for instance. Or near your grain mill or stores...

Cheers!

 

[Yeastieboy]

Again, it's so easy to cover with some foil. What is gained by not covering? Why leave it wide open like some sort of mini cool ship?

 

[VVbrewery]

I use one of these silicon foam stoppers. I boil the wort in the flask and the steam sterilizes it. Then it filters the critters out as the wort cools. Just make sure to use Fermcap or other anti-foam stuff to prevent boil overs.

https://www.williamsbrewing.com/Search.aspx?k=foam+stopper

 

[Gustatorian]

I use one of these silicon foam stoppers. I boil the wort in the flask and the steam sterilizes it. Then it filters the critters out as the wort cools. Just make sure to use Fermcap or other anti-foam stuff to prevent boil overs.

https://www.williamsbrewing.com/Search.aspx?k=foam+stopper

You put the flask over a flame and boil the wort with the flask? Aren't you worried about breaking it? You add the fermcap to the worst before you boil it?

 

[ahawk]

I cover mine with sanitized sprayed down tin foil. It's so easy to do, so why not just do it, right?

 

[Totally]

Another one for a square of sanitized foil. Quick and easy, never had any issues.

 

[VVbrewery]

You put the flask over a flame and boil the wort with the flask? Aren't you worried about breaking it? You add the fermcap to the worst before you boil it?

Those flasks are made to be used over a direct flame. That's what they're used for in laboratories. Though I have heard of problems with some of the cheap Chinese/Indian ones breaking I have two I've done this with many times with no problem. Yes you add a couple drops of Fermcap to the wort before boiling. I still keep an eye on it though.

From the Williams brewing web site:
If you make yeast starters, our heat-resistant glass Erlenmeyer flasks are perfect for preparing the starter solution and growing the yeast. Put the bottle directly on your stove to boil and then cool (with the bottle sealed with a foam stopper) before adding yeast to minimize the chance of infection. Withstands temperatures of over 700 F. A gas stove is recommended, as electric burners can cause the glass to crack.
Note: I use a glass topped electric stove that distributes the heat over a large area and as I said never had a problem.

 

[brick_haus]

On the electric heat note: I have had flasks crack when heating on a hot plate in the lab. I recommend using gas burner to heat.
I too use sterilized foil to cover my starters...