I've got a package leaflet for cough lozenges in Russian saying that it's ok if they get covered in this white haze/mist (get opaque) in time. What do you call this mist? Or maybe there's a name for this process?
The lozenges get cloudy. Here’s an example of this expression:
After two years, the cough drop begins to look cloudy, it becomes softer and stickier, loses shape and begins to "flow into the cracks and crevices" of its wrapper, a Warner-Lambert spokesman says.
The white haze that forms on the outside of hard candy over time is called "sugar bloom." It's caused by humidity over time essentially dissolving the surface of the candy and then the sugar recrystallizing, making it white.
This isn't to be confused with the white haze that you sometimes find on the outside of candy that is actually powdered sugar that the maker has sprinkled it with to keep the candy from sticking to each other.
"Graining" is another term for it. I've heard some of my friends say that "graining" is for hard candy and "sugar bloom" is for chocolate, but I don't know that's true because I hear "sugar bloom" used more often and for both, but I do know "graining" is another thing people call that white haze that forms specifically on hard candy that's gotten old or has been exposed to a lot of humidity.
I know this from making hard candy every Christmas since I was a kid -- just from hearing my mom and family and friends talk about it over the years.