When pouring a drop or two always goes over the edge onto the threads of the opening. I stored the bottle in the pantry for a while then later decided to start keeping it in the fridge (because I assume a chilled Baileys will be less dominant in a baby guiness so the coffee taste prevails more).
I noticed a nasty charcoal colored slime building up around the neck/mouth of the bottle. It’s a black bottle which hides that, but wiped it off with a napkin and saw the black color. Of course that also means that whatever that black stuff is, it mixes with whatever I am pouring unless I wipe it off every time before pouring.
WTF is it? Ingredients of standard Bailey’s are:
Irish whiskey, cream, sugar, and a blend of cocoa and vanilla flavors.
So I wonder if that is not spoilage, perhaps it’s just cocoa and vanilla additives. Or perhaps the aluminum cap reacting. I’ve noticed that dishwasher-unsafe aluminum turns black in the dishwasher. So maybe it’s the cap reacting with something in the Baileys?
Personally I’d not trust it. Sugar and cream are choice substrates for all kinds of molds and bacteria, the alcohol content may be enough to protect the inside, but outside the bottle is prime conditions for that alcohol level to come down, and you can get nasty stuff even in low temperature conditions.
New bottle, and make a point of wiping the neck down if you get drips.
When I bartended I always made sure to keep the Bailey’s refrigerated. It’s basically a mildly alcoholic chocolate milk. That and the vermouth needs the fridge. But to answer your question; yes, almost certainly an indicator of spoilage.
I have similar buildup on my bottle of simple syrup (I used an old Monin bottle) and a couple of other spirits and liqueurs. I think it’s the sugar instead of other additives, but IDK if this is some kind of chemical reaction (I only get this buildup on bottles with metal screwcaps) or just spoilage.