Stir Plate

[Thedagem]

How do you use one the right way? This is an honest question, but allow me to explain. I'm not so dumb as to not know that the stir bar goes into your flask with your starter and the flask goes on the stir plate and you turn it on. That much I know. But every time I see it done they simply cover the top with aluminum foil. Why? Why not an airlock? I understand that you're trying to get oxygen into the starter, but wouldn't harmful bacteria and mold be able to get in as well being that there is no airlock? If there is something I'm missing about aluminum foil please do enlighten me. I plan on purchasing a stir plate in the very near future.

 

[Bear419]

I believe it is b/c the bad things you want out of your starter really only fall down not up. So if you have some foil sprayed with star-san around the top that is sufficient to keep anything from getting into your starter. I've made several starters this way and they have been fine.

If you want to be extra safe they make foam stoppers that let air in but filters the baddies out.

 

[OldBunny]

I use foam stoppers that I get from William's Brewing. They pretty much seal the flask against "critters" but allow air to get in. I sanitize by dipping them OneStep or StarSan and then squeezing them dry.

 

[NotTechnicallyLegal]

Bad guys can't fly up.

http://science.howstuffworks.com/innovation/scientific-experiments/scientific-method5.htm

Some of his experimental flasks are on display in Paris, and have gone over 100 years without becoming infected. Aluminum foil isn't quite as elegant as a swan neck flask, but still accomplishes the same thing.

 

[Thedagem]

Thanks guys, I didn't know they couldn't fly up. That's actually quite fascinating. Thanks a ton.

 

[Bear419]

Thanks guys, I didn't know they couldn't fly up. That's actually quite fascinating. Thanks a ton.

http://www.amazon.com/Yeast-Practical-Fermentation-Brewing-Elements/dp/0937381969

Here's a great book on yeast that goes into issues like this in a lot of detail. Definitely worth the $11 IMO.

 

[jbeukelman]

This is something that has never really made sense to me. A starter is simply a small batch of beer. So if the nasties don't fly up, then why don't we just put a piece of foil over our fermenter? Why air tight?

Is it simply to contain the krausen?

 

[emjay]

This is something that has never really made sense to me. A starter is simply a small batch of beer. So if the nasties don't fly up, then why don't we just put a piece of foil over our fermenter? Why air tight?

Is it simply to contain the krausen?

Theoretically, to keep oxygen out. It's good for starters, but bad if you want drinkable beer.

That being said, oxygen doesn't make it to fermenting/fermented beer (in the primary) all that easily anyways, especially if it's not being agitated. I brew my saisons and hefeweizens using only a piece of foil, as the lack of additional pressure encourages ester production. Making it airtight and adding an airlock or blowoff tube increases the pressure in the vessel equal to the height of the water column, reducing ester production... fermenting at much higher pressures in kegs or conicals is becoming an increasingly popular way of producing a "clean"-tasting beer.