Menu Icon

Looking for homebrewing gift ideas? Check out our previous gift guides here or here!
Also, if you enjoy BrewUnited, please consider doing your Amazon shopping via our affiliate link!

Disgusting Mold Covered my Carboy, or, it's What's Inside that Counts

Posted by homebrewdad on 5/29/2014 at 05:47:10 PM


At the end of March, I brewed a batch of one of my "house beers" - Frolicking Friar.  It's the famous Revvy clone recipe for Leffe Blonde, which, incidentally, is a delicious beer.  I will admit to having a bit of a soft spot for this particular brew, as my mind combines two of my biggest interests in it - beer and Disney World.  You see, I had this beer for the first time at the Epcot Food and Wine Festival back in 2011, which opened my eyes to Belgian beers. 

At any rate, I brewed this beer (with the help of my three little boys) at the end of March, with the intention of leaving it in primary for four weeks.  My primary fermentation chamber (a mini fridge/STC-1000 temp controller combo) was occupied with the lagering of a bock, so I pulled my Mother of a Fermentation Chamber out of mothballs and put it to work.  I discovered anew what a beast WLP530 is; I had gotten spoiled by not needing a blowoff with other beers, thanks to temperature control, but the 530 was having none of that (hello, foamover!).  So, I converted my airlock to a blowoff (by connecting a hose to the inner valve of the airlock), dunked the other end into a big bowl of starsan, and once fermentation was done, I promptly forgot about it. 

Experienced brewers may note that I did not mention swapping back to an airlock or changing out the blowoff bowl, and know where this is going. 

Four weeks stretched into six, thanks to the chaos of baseball season (with four boys playing) and having a new baby around the house.  I wasn't concerned, though; I've left beers in primary with no ill effect for far longer than six weeks.

Three weeks ago, I decided to stop procrastinating and go bottle my beer.  That Saturday night, I opened my fermentation chamber to the scene of a nightmare.

Mold.  Dear God, where could so much mold come from?  The streaks of dried beer on the sides of the carboy from the krausen eruption were now artistic lines of fuzzy yellow growth.  The airlock itself had gone beyond yellow - it was full on brown, and thick with the stuff.  The tube itself had yellow on both the inside and outside surfaces for several inches down away from the carboy.  The bowl was covered in a disgusting slimy pellicile with huge hairy growths on top of that.  Yes, gentle reader, in effect, I had mold on top of mold!

Also, I would be remiss if I did not mention the smell.  It was the smell of rot, of decomposition... a sickly sweet pungent sourness that crawled into nasal passages and refused to leave. 

For more than a few minutes, I debated what to do.  The mold on the outside of the carboy was so bad that I could not truly see inside of it.  I was terrified that the growth was also on the beer, and that my delicious brew would not come to be.

Gagging, I disconnected the hose from the airlock and carried the bowl upstairs to clean it out.  I discovered a few interesting facts in the process, such as the fact that the pellicile was so thick that it got hung up in the drain, requiring me to break it up with a butter knife before it would wash away; the fact that there was a slimy layer of what looked like yeast at the bottom of the bowl that stunk, if possible, even more than everything else; the fact that my family did not appreciate the odor I had inflicted on them.  Indeed, the stench lingered for more than an hour, despite scrubbing, hot water, soap, and the lighting of scented candles.

I then filled a bowl with hot starsan solution and carried it downstairs.  I pulled out the airlock, then used a rag soaked in starsan to carefully clean the mold from the opening (to keep it from dropping into the beer).  I then scrubbed and outside of the carboy a couple of times until most of the visible mold was gone.  Trying to ignore the distinct slimy feeling, I picked up the carboy and carried it upstairs.

The beer itself did look and smell fine, so I left the carboy to settle for a few hours (and myself to apologize several more times to my family) before bottling.  That night, I bottled as normal, then cleaned everything thoroughly (you would not believe how much that tubing stunk, even after cleaning AND boiling it).

A few days ago, I opened the first bottle of the batch to discover a clear, delicious Belgian blonde ale.  Rocky white head, fruity esters, dry finish; just as I had expected when I first brewed the beer. 

So yes, the nasties were kept out of the beer by the airlock/blowoff.  Despite looking (and smelling) disgusting, the beer itself was fine.

And finally, if I laze out and neglect to clean up again - and thus subject them to that kind of smell - I may well be the subject of bodily harm from my family. 

Tags for this post: mold, fermentation, beer, bottling, Belgian, ale, stink

Please log in to comment on this post
Don't have an account?


Oh nooooooo!!!

posted by Brulosopher on 6/02/2014 at 06:17:35 PM

So what would you have done differently? After the blow-off, should a brewer replace the dirty airlock with a clean one? I'd like to learn from your experience.

posted by Springlanding on 7/06/2014 at 08:08:19 PM

After the blow-off, I should have indeed replaced the dirty airlock with a clean one. I certainly should not have left the blowoff vessel full of nasty byproducts. Also, I should have wiped down the carboy with a soapy cloth, then repeated until it was more or less clean.

Leaving the junk behind was a mistake, for sure!

posted by homebrewadad on 1/10/2015 at 10:11:18 PM