Why store wine bottles on their side?

This is one of those wine rules that has a solid scientific basis — but also comes with some modern exceptions worth knowing about.

Natural cork is made up of millions of tiny air-filled cells. That cellular structure gives it the flexibility to seal a bottle neck perfectly. But it only works when the cork stays moist. Laid on its side, a bottle keeps wine touching the inside of the cork, keeping it swollen and airtight. Stand the bottle upright for months, and the cork slowly dries, shrinks by 1–2 mm, and starts letting oxygen seep in.

Research from the Portuguese Cork Association found that natural corks stored vertically for over 6 months lost up to 15 % of their elasticity — dramatically increasing the risk of premature oxidation.

Here's the modern twist: screw caps (increasingly common, especially from Australia and New Zealand), synthetic corks, and glass stoppers don't dry out. If your bottle has one of these closures, store it however you like — standing, lying, at an angle, it genuinely doesn't matter.

Sparkling wines are an interesting edge case. The internal pressure (about 6 atmospheres in champagne) keeps the area near the cork humid even when stored upright. Many experts say vertical is fine for short-term storage. But for long-term ageing, horizontal is still the safer bet.

One more detail: a slight downward tilt (about 5°) is considered ideal by some sommeliers. It maximises cork contact while letting any sediment settle in the belly of the bottle, making decanting easier later.