I kegged a cider that had been aging in a carboy for about 9 months today.
I know there was some contamination in that cider because:
1) The apple juice I used was unfiltered, unpasterized, contained no preservatives and had a best before date of 4 days in the fridge even though I bought it fresh from the farmer's market. Bacteria/wild yeast fest!
2) After about 2-3 months in the carboy it developed a whitish peliculite on the top.
3) I also noticed some ropey/stringy looking white stuff floating, but they disappeared at some point when I moved the carboy a little..
4) Finallly, I also noticed a blueish look on the glass headspace, but thought it must have been some kind of illusion.. I was more concerned with the white stuff!
Today I had a taste for the first time. I was pleased with it and kegged. The unfiltered apple juice had become a crystal clear, very dry and acid cider.
Then comes to weird part: as I was cleaning the carboy, I noticed the transparent glass had become BLUE! What the hell!?
What in the world could make a carboy turn blue? Can some bacteria turn my carboy blue/green?
Here is some pictures. On the left, an identical, dry carboy for reference. On the right, the carboy that held the wild cider for 9 months. I took the picture as I was cleaning and there is a gallon water at the bottom that makes it look more greenish near the bottom, but the tint is pretty much the same all over. There is no cleaning agent in the water, it's just clear rinsing water.
Since the tint seems perfectly equal all around the carboy, I can't reasonably conclude it is a bacteria that tinted the whole thing, including the headspace.. the only thing I can conclude is that that damned carboy has always had that blue tint.. ?!?
But still.. I am PRETTY sure those two carboys WERE identical.. Sure, it's been a real while since I've seen both of them empty side by side.. But I swear they were identical...!
So, can anyone confirm I am crazy and tell me that these carboy do come in a green tint?
Or do you have another explanation?
The carboy is soaking in oxyclean now, but is still green looking