I noticed my bottle caps are turning black on the side exposed to the beer. The black discoloration is under the plastic coating on the caps ( I scraped the plastic off with a knife). The beer was bottled end of november 2021. Not terribly concerned as its on other side of plastic not touching beer. Just seems weird. The caps are from an overrun of caps from either phillies or pirates. Caps are like 5 years old…got a gazillion of em cause they were cheap. I bottle aged chimay blue and red clones for over a year (about 4 years ago) and never saw this before.
@mikem do you soak you caps in sanitizer before use? I’ve seen this occasionally on capped. bottled or jarred goods. I don’t think it’s a cause for alarm.
Good point. I notice mold on the lid of the bucket i have sanitizer in if getting old. I was figuring they got wet or damp in storage at some point. Probably why they were sold cheap.
they are submerged in sanitizer from less than a minute to hours. I will bottle 8 today and will use fresh sanitizer with short contact time on 4 and old hour soak on other 4 to see if different. I mix up sanitizer in 1/2 gallon increments so sanitizer goes quickly. Never had pH get too high and I discard when foaming drops or it looks too cloudy.
My thoughts are- if it was caused by moisture from sanitizing or beer obviously there is contact between the now carbonated beer and whatever it is. Would make no sense that moisture would be able to get once but never again.
just throwing it out there but does mold need O2 ? Are they O2 absorbing caps? maybe some spores got under the cap and when the absorbed the O2 they grew. Im thinking once the bottles condition and the O2 is no longer present it wont affect the beer?
Did speak to a brew friend of mine he only bottles his brew. On every beer bottle cap he pulls of the plastic than sanatize them. He had mold before. But after removing plastic. He never had that issue again
squeegeethree I did some further investigation and the black stuff does not dissolve in water or break apart. Its hard. Looks like corrosion. The beer was 4 months old. I will find out if the soaking of caps in starsan is a bad move in 4 months. I have not observed it at two months.
The starsan is corrosive due to low pH. I had it eat up my old autosiphon rubber seals in an old version of NB autosiphons. I would always clean it, sanitize it and leave the starsan on it. Now I sanitize then rinse it off with water.
I wont remove the plastic as suggested because its real tough to get off…almost cut myself a few times. Thanks for the ideas.
I think yer onto sumptin’… I will wonder out loud… Will mold thrive in a low pH environment? Metal/tin do not like it… So, since the caps have soaked in an extremely low pH, I will suspect corrosion… not mold… " Hey! Can I get a rusty capped brew around here?"… Clowning, eh…
Sneezles61
