Mold on beer surface?

John C

Barley Legal Member
I have encountered something i have never seen before. I think it is mold on the surface of my fermented beer. See attached picture.

I ferment in my garage during the winter with a heat belt to maintain the temp profile I am going f20210606_202009.jpgor. In the summer however it becomes somewhat problematic but am generally able to keep the temp at 70 though insulation.

With the hot days I discovered this white balls and thend on top. I racked the batch and sampled it. It seemed fine and ther was no mold smell.

Anyone else experience this and know what it is?

Matt Talbot

You have some wild stuff happening in there. Literally. It is definitely infected with something that got into your carboy from your local environment.
Maybe it will turn out good...


Tom Carola

Barley Legal Member
This occurred in the primary? You'll want to look into thoroughly cleaning and sanitizing all your cold-side equipment- especially what you used to transfer from your kettle to your fermenter. Might even be worth it to replace any tubing that you can't guarantee a thorough cleaning with.

What are you using to chill? immersion chiller- or a counterflow or plate?

Are there any valves between the kettle and the fermenter? If so, might be worth taking them apart and giving them a good cleaning.

Warmer months mean that there is more microbiology in the air- so every surface needs a good cleaning. I even give my yeast packs and the scissors I use to cut them a quick dip in star-san.

Frank Hiller Sr

Competitions Coordinator - 2018 Brewer of the Year
Yes, that's a Pellicle. So without a lab test, its impossible to know exactly what the infection is. I've had one too where the beer tasted good, so I racked and carbed it and it was ok. Whatever it is, it usually consumes the sugar remaining after the yeast is done, so rack it, carb it, keep it chilled and consume it quickly.

John C

Barley Legal Member
Good call guys. That is what it looks like. To Frank's and Matt's point, I racked it and sampled it. Taste was fine. The FG also was lower than what I was targeting (1.006 vs 1.012), so your prediction of more sugar consumption proved right..

Its in the keg and under gas today. We'll see who things go around the 4th!
Thanks guys.