I put an irish bar's baileys into my morning's black coffee I kept warm in a Stanley thermos. But after an indeterminate amount of time (between 10 mins to an hour), some of the milk curdled.
Is that normal? Should I have been concerned? Is it because my coffee turned out that acidic?? We use a french press and preground beans. I haven't taken a look at where he buys his bean grounds, but offhand it tastes like a medium roast.