Life expectancy of corks

[uncle tom]

It is nearly six years now since I set out to turn a ramshackle and un-catalogued collection of bottles into something more ordered and managed.

This started with the rather simple objective of creating a cellar that could, (amongst other things) yield a vintage port bottle of 100 or more years of age each year, for at least a century hence.

This objective rather focused my attention on the matter of corks, their longevity, and periodic replacement - if necessary.

This was very much an exercise in groping in the dark; the little that has been written on the subject is generally unscientific; and re-corking old bottles is a problematic exercise.

What is the mean life expectancy of a cork? If you laid down a dozen new bottles today, and left them undisturbed for 100 years, how many would (on average) then be in good order?

No-one really knows.

While original cases of old well cellared port do turn up from time to time, unopened cases over 50 years old are extremely rare, and with old stashes it is impossible to know if the previous owner was in the habit of drinking the best bottle, the worst ”“ or just the first that came to hand.

In the absence of good information, I have set out to secure a better understanding of corks, and their longevity; and whilst I am sure that in another five years I will have a much better understanding; I thought I would share a few thoughts and conclusions.

I suspect that corks have three main classes of deficiency, with regard to maintaining a seal:

1) Structural defects ”“ corks that have fissures or other failings that compromise the seal.
2) Insufficient resilience ”“ corks that do not press firmly enough against the glass.
3) Lack of integrity ”“ corks that are prone to crumbling.

The first category tends to show its hand early, often with a wet or damp selo. If a bottle survives to great age, it is likely to be heavily ullaged, and the cork may fracture lengthways when drawn.

The second category generally survives well at first, but after three or four decades, the cork is unable to handle its requirement to maintain a full seal. Such a cork may draw well, but emerges wet. The bottle it came from may show signs of seepage, or advancing ‘dry’ ullage.

The third category is typified by the corkscrew ripping the centre out ”“ even when quite young ”“ and leaving the rest in situ. With old bottles, the crumbly wine impregnated mass may become quite firmly attached to the glass.

I have found some association between the third category and heavy bottle stink in younger bottles, but this could be coincidental.

Category three corks rarely show seepage, but appear to indulge a gradual and progressive ullage rate.

How many corks are affected?

This is hard to determine. Some old cases can appear to be entirely free of defective corks, but this is relatively rare. Even rarer (mercifully!) is the case where every cork is duff.

There are also red herrings. Some cases have very variable original fill levels (and some recent bottlings have original levels that are woefully low). Sometimes a messy bottling line or leakage from another bottle has resulted in a wet selo, causing a false impression of seepage.

On average though, I suspect that three or four corks in every case are less than perfect.

But that leaves eight or nine good ones!

Having recorded the levels and condition of my bottles with some care; and then targeted the weaklings for consumption - ‘survival of the fittest’ - I have reduced the number of new leakers to a level that is well below that which I would have once hoped for, and, moreover, a level that does not unduly dictate the agenda for consumption.

I originally presumed that cork failure was a steady and progressive event that would gradually accelerate with the passage of time, but that now seems not to be the case. Once the weaker corks have been identified, and the bottles drunk, those that remain seem to have an impressive life expectancy.

There is still a place for re-corking; but I now believe that most of my centenarian victims will have their original corks drawn.

Tom

[JacobH]

I wonder how the quality of corks has improved over the decades? One would hope that it (and bottling standards, generally) are much better now than 50 years ago. Especially since shipping by pipe was eliminated. I remember reading an article about Vega Sicília which said that they had almost eliminated cork problems by extremely rigorous testing of individual corks which results in the majority of them being rejected. Vintage Port is pretty much in the same category as Vega Sicília in terms of price and quality but far exceeds it in terms of ageing potential, so I would hope the research into cork making it undertakes is at the top of the game.

There’s a post on the Graham’s blog about this, listing the work they do, which you might find interesting if you have not seen it yet.