The closure debate was, for about fifteen years, one of the fiercest arguments in wine. It has largely gone quiet, not because it was resolved but because both sides settled into territory.
Screwcaps dominate in some countries and market segments. Cork dominates in others, particularly at higher prices. And the technical case, which was pretty clearly won by the screwcap, turns out to have been only part of the question.
The problem cork had
The driver of the whole argument was cork taint, caused principally by a compound called TCA — 2,4,6-trichloroanisole.
It forms when chlorophenols, which can be present in cork bark or from cleaning agents and treatments, are transformed by fungi. The resulting compound is detectable by humans at extraordinarily low concentrations, in the region of a few nanograms per litre.
At noticeable levels it smells of damp cardboard, wet dog or mouldy basement. At lower levels it doesn't smell of anything identifiable — it simply strips fruit and makes the wine seem dull and short. That subclinical taint is arguably the bigger problem, because the drinker just concludes the wine wasn't very good.
Taint rates were historically estimated at somewhere in the range of 2 to 5 percent of bottles, with some claims higher. For a producer, that meant a meaningful fraction of every vintage arriving faulty through no fault of their own.
What screwcaps fixed
The screwcap — technically a roll-on tamper-evident closure with a liner — eliminates TCA from the closure entirely, though it can still reach wine through other routes such as contaminated cellar materials.
It also delivers far more consistent oxygen transmission. Natural cork varies considerably from piece to piece, meaning bottles from the same case can age at noticeably different rates. Screwcap liners can be manufactured to a specified oxygen permeability, so bottle variation drops sharply.
And it's easier to open, easier to reseal, and cheaper.
On every technical criterion, that's a clear win, and the research from Australia and New Zealand where adoption was fastest supported it convincingly.
The reduction question
The main technical objection to screwcaps was reduction — sulphurous, struck-match or rubbery aromas that develop in wine with very low oxygen exposure.
This was a real issue with early screwcap adoption, particularly with tin-lined closures that transmit almost no oxygen at all. Wines that would have been fine under cork developed reductive characters.
It's largely been addressed through two routes. Liner technology now offers a range of oxygen transmission rates, so a producer can select one appropriate to the wine. And winemakers adapted their practices — managing copper additions, controlling sulphur levels at bottling, and adjusting how much oxygen the wine receives before closure.
So the objection was valid and has mostly been engineered away, which is what usually happens with new technology.
Why cork survived
Given all that, the persistence of cork at the top of the market needs explaining, and the explanations are mostly not technical.
Ritual. The act of opening a bottle with a corkscrew is part of the experience. The sound, the small ceremony, the physical object. Screwcaps deliver wine efficiently and remove something people apparently value.
Signalling. Because screwcaps were adopted first at lower price points, they acquired a downmarket association that has proved sticky. A producer selling an expensive wine faces genuine commercial risk in using one, regardless of its merits.
Long-term ageing uncertainty. The honest technical caveat. Screwcaps have been in wide use for around two decades. We know how cork behaves over fifty years because there are fifty-year-old bottles. We're still finding out about screwcaps at that timescale, and for a wine intended to age for decades that's a real consideration.
Sustainability arguments. Cork oak forests are genuinely valuable ecosystems, harvesting cork doesn't kill the tree, and the forests support considerable biodiversity. There's a legitimate environmental case for maintaining demand, though the comparison with aluminium production is complicated and depends heavily on how it's calculated.
How the cork industry responded
Worth noting because it's the most consequential development. Faced with an existential threat, the cork industry invested heavily in quality control.
Individual cork screening using gas chromatography, steam treatment processes that remove TCA, and much tighter production standards. Taint rates from major suppliers are now reported to be dramatically lower than they were, though independent verification across the whole market is harder to come by.
That's a genuine improvement driven entirely by competitive pressure, and it's the strongest argument for having had the fight in the first place.
The other options
Technical corks — agglomerated particles bonded together, with the individual particles cleaned — offer much of cork's appearance and behaviour with lower taint risk, at moderate cost. These have taken a large share of the mid-market.
Synthetic corks have declined somewhat, having had issues with oxygen transmission over time and with being difficult to extract.
Glass closures with a seal exist and are elegant, expensive, and niche.
What I'd want
For anything I'm drinking within five years: screwcap, unequivocally. The consistency is worth more than the ritual, and the risk of a spoiled bottle is close to zero.
For something I'm keeping twenty years, I'd probably still take good cork, mostly because that's the closure whose long-term behaviour we actually understand. That's a conservative position rather than a confident one, and I'd expect it to look outdated within another decade.