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Is it Yeast or Not?

I stepped up a starter last night and boy it took off quick! Within an hour the foam was blowing the foam stopper out of the flask!

So I put a washcloth over the stopper and rubber banded it down for the overnight.

I got up the morning and there was this yeasty looking sludge all over the stopper and squeezed through onto the washcloth. It’s the same stuff that forms after a blowout in a fermenter.

Is that stuff yeast or is it just a sludgy bi-product of the foam?

It looked and smelled like yest, so I scraped it off an put it back into the starter.

I would find it hard to believe that the foam stopper would break down by something like yeast sludge. I’m no chemist but that sounds unlikely.

On another note, check out Fermcap S. The stuff is nothing short of amazing. My 1.090 IIPA didnt even reach the airlock in a 6 gallon carboy.

Put a drop or two in your starter and you’ll barely see a krausen form

The stopper didn’t break down…it just blew out.

But my question still stands - is that sludgy stuff actually yeast that I should be trying to salvage or is it just a bi-product of the fermentation?

When the stuff blew out of the flask it was an assortment of proteins, yeast, malt, and water. Once it left the flask it picked up an unknown number of wild yeasts and non-yeast microorganisms. I’d not use the starter if you put the stuff that escaped the flask back into it.

yeah, its essentially the krausen, which is what is described above. Next time, just spray the outside with sanitizer, wipe it off, and leave the inside as a somewhat closed environment before pitching. To be on the safe side, I would grow up another (even on brewday) or use dry yeast for your beer.

You mentioned blow off and this is the same thing. Would you have put it back into the fermenter? I agree with Old Dawg about it sitting out collecting undesirable wild yeasts. Not sure I would use this starter.

Hmm…good thoughts. Didn’t think about any of that.

I’m not too concerned about contamination…the bit input back in was in the underside of the stopper inside the flask, still under sanitary cover. Besides, it’s kinda late now to spin up a new starter…brewing on Saturday and I don’t have anymore of this yeast…

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