science question

[derekcw83]

Is it really avoiding infection by using a blowoff tube?

Can't the blowoff vessel become infected from being exposed to air and sometimes being introduced with yeast and beer and extra stuff from the fermenter? And then, what is preventing that from traveling through the blowoff tube?

Obviously the tube is full of co2 continuously flowing, but what if the flow slows down, or even just being moist and possibly infected with crap in the blowoff jug, can that travel into the fermenter? I have seen moisture collect in the upper walls of the fermenter before. Maybe it can also collect in the tube.

 

[IslandLizard]

That's why we fill the blowoff jar/bucket with Starsan or other sanitizer.

And you're right, moisture condenses on the lid and sides inside the fermentor exposed to air. But the vessel is supposed to be sanitized before you pour the wort in, so not much can thrive in there. The blowoff tube and jar are also sanitized.

Bugs don't move by themselves, they need an air flow or an other outside physical means to get transferred. So a suck back could transfer bugs when the sanitation barrier fails.

 

[GPP33]

If I get any actual overflow I'll switch to a regular air lock as soon as things settle down. During the heat of fermentation when you are actually utilizing a blow off tube for it's intended purpose there's zero chance anything is making its way back up the tube.

 

[kh54s10]

I start every fermentation with a blow off setup. I only change back to an airlock if I need the blow off tube for another batch. I have had the blow off catch container grow a good layer of mold once. The beer was not affected.

If you sanitize, and don't get the blow off sucked back into the fermenter there is really not much to worry about. The bugs cannot fly up the tube, over the top, and into the beer. They fall. So they need to be carried there along with something (air or suck-back) entering the fermenter.