Why do some wines have corks and others screwcaps?

It is a closure choice, not a quality signal — and on the evidence, screwcaps perform better for most wine.

Natural cork is bark from the cork oak, harvested without felling the tree. It has been used for centuries, seals well, and allows an extremely small, slow exchange of oxygen that many believe contributes to how a wine develops over years.

Its significant flaw is cork taint. A compound called TCA, formed when chlorine compounds react with fungi in the bark, gives wine a musty smell of damp cardboard or wet dog and strips out its fruit. It affects an estimated 1 to 3% of cork-sealed bottles — meaning roughly one bottle in a case of a hundred is spoiled through no fault of the winemaker. Cork producers have reduced the rate considerably, but not eliminated it.

Screwcaps eliminate cork taint entirely, seal consistently, and can be engineered with liners that permit a chosen rate of oxygen transmission. They require no corkscrew and reseal, which matters for a bottle you will not finish. Australia and New Zealand adopted them very widely, including for premium wines.

The resistance is largely cultural. Screwcaps were first used on cheap wine, and the association persists. Blind tastings do not support the idea that cork produces better wine.

There is a genuine open question about very long-term ageing — decades — where cork has a track record screwcaps have not yet accumulated. For the vast majority of wine, which is drunk within a few years, it is not relevant.

Synthetic corks avoid taint but seal less consistently over time.