Glass grew from a simple image: a quiet Friday night, the porch light on, a bottle sitting on the top shelf, and the sound of ice hitting the glass.
There is nothing complicated about that moment, and that's part of what gives it weight. When the noise of the day disappears, small sounds become noticeable. So do thoughts that are easier to ignore when everything else is moving.
The song uses that quiet as its center. It isn't meant to tell the listener exactly what to feel. The image can belong to anyone who has ever sat alone long enough for a memory, a decision, or an old truth to catch up with them.
That approach is central to Dave Rylan's songwriting: start with something real enough to recognize, then leave enough space for the listener to find their own life inside it.