Sometimes in old movies, someone drinks something alcoholic, then flings the glass, or goblet, shattering it . . . often into a fireplace. What exactly does this mean, other than “I’m so rich, I can afford to buy new glasses all the time.”
It’s not just in old movies – it’s an old tradition.
I personally suspect it’s so that the toasting glasses, once used to “dedicate” the toast, won’t be used again (and can’t “dishonor” the toast). But I’ve never read anything about that.
It’s undoubtedly related to the tradition of breaking the glass at the end of a Jewish wedding.
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It gives more sincerity to the toast since no other one can be made with the same glass.
It’s exactly the same as throwing any other object (people throw stuff 100x more often on camera than in real life) or being so mad that you sweep everything off a desk. It’s simple visual shorthand for the intensity of emotion going on. It’s silly and doesn’t happen much in real life, but it looks good on camera no matter how much of a cliche its become. Just of the million similar things that are long-standing metaphors in movies.
It can also be done as a salute, as in the case of a truly world-class pun at Callahan’s.