Yeast starter blowing off

I stepped up to a 2 liter yeast starter last night. I woke up this morning and it's raging. I used a flask with foil, so the blowoff is coming out of the flask. I'm gonna try to rig a blowoff tube, but has it risked infection at this point? The foil is still sitting on top, but a decent amount of krausen has escaped.

If the foils is still on top and there's lots of CO2 comng out, I wouldn't worry about any random yeasts/bugs getting in. I'm just curious about this starter - I've never had a starter form a decent krausen, let alone go wild.

Pappers said:

If the foils is still on top and there's lots of CO2 comng out, I wouldn't worry about any random yeasts/bugs getting in. I'm just curious about this starter - I've never had a starter form a decent krausen, let alone go wild.

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I did a 1.5L starter last week. Didn't go crazy or anything but still fermented out. Then I cold-crashed and decanted the spent wort. Last night I poured 2L of fresh wort on top of the yeast cake to step it up. Woke up this morning to some foam escaping, and an obviously vigorous fermentation. Not sure if it's technically krasuen, but there are several inches of foam atop the wort. I should also mention that I came somewhat close to maxing out the space in my flask.

Another question I have is, how much yeast will I lose from this?

You shouldn't lose too much yeast. I had a starter of Bells Two Hearted yeast do the same thing a couple of weeks ago (what a mess). Pitched it and it was fine. No worries.

OK, so it's been 36 hours and this thing is still raging -- looks like a primary fermentation. I've never experienced this before. I was hoping to cold crash it tonight so I could brew tomorrow. Would it be bad to put it in the fridge to cold crash before it fermented all the way out? Or should I just pitch it all tomorrow (2L) ?

When its happened to me, I've cold crashed it, decanted the starter wort, and pitched. If you are not worried about flavor impact, then just pitch the whole thing.

Update -- I pitched this starter into a batch of IPA yesterday. While it was going gangbusters as a starter, it has shown absolutely no signs of life in the primary so far. I had to pitch on the cool side (60F) because I cooled the wort too quickly. It's been 18 hours, usually I have good krausen by this point. We'll see how it goes.

This happened to my kolsch. I ended up brewing a day early because of a volcano starter. I should have placed it in a pan and waited another day because my regular fermentation took only 12 hours to krausen, but it's been uber sluggish.

What strain was it?

My starter just did the same thing. It was WLP001 yeast, 2000ml on a stirplate:

Funny, I also used WLP001, in the same exact flask. Looks like you took a pic from my basement!