What the glass cannot stop
A bottle is not a sealed room. Light reaches through glass more easily than we like to admit, and the damage it leaves is often quieter than heat, movement, or time.
Of all the risks to a bottle, light is the one most easily forgotten — it does no visible work until the wine has already paid for it. We watch temperature, fill, cork and capsule, and leave the bottle sitting where the sun can find it. Glass protects the wine, but it does not make it invisible. Clear glass offers the least defence; darker glass helps, though it is not a licence to test it. Direct light warms the glass, unsettles the liquid, and alters the wine's more fragile compounds — and unlike a cork that can be inspected or a temperature that can be corrected, what light takes cannot be given back. The damage is quiet. The label still looks correct, the capsule intact, the fill persuasive; only the wine has changed, aged in public over hours of careless display. Some bottles show it as a tired, exposed character, others simply as a loss of freshness and definition. This is why serious storage is partly an act of darkness — not secrecy, but protection. A great cellar is a dark one, and deliberately so: glass left to do its work, wine never asked to perform before it is opened.