Half bottles vs normal-sized bottles

In some of the en Primeur offers of the Society, I have noticed that when the same wine is offered in normal bottles, or half bottles, the drinking dates are the same for both half and normal bottles. My understanding (no references, just something read or heard) was that the smaller bottles proportionally had more air in the space between cork and liquid, and therefore the wine may be oxidised more, so one would have to drink it earlier i.e. the wine would not last as much. Is it considered, in those offers, that the space between cork and liquid in both bottles is proportionately the same?

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I don’t think so. I think you’re right - the volume of the liquid compared to air has a material effect on the rate of ageing. The bigger the bottle, the slower the ageing (as far as I understand it), so you would have thought half bottles should have a shorter drinking window. One offer where you can see this is the 2018 port en primeur campaign, the half bottles have a shorter drinking window.


Are bottles of wine airtight until you open the bottle?
Normally we drink a half bottle at a meal and the rest the next day. If we opened a half bottle we would drink it all at one meal. Consequently that would be better?

I don’t think it’s a question of better, just different / changed.

Not always…some wine benefits from a day more…best way with a full bottle is to keep an empty half bottle and use it for the half that’s left, and just keep reusing it. The half bottle that is…


I bought half bottles of Thalabert in the Rhone EP offer this year, and the WS notes in my order now show a slightly earlier beginning and end to the drinking window than the full bottles (2024-35 vs 2026-39). So it seems they do take this into account.

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Many thanks to all that answered.
As I thought, in my ignorance (oh, yes, my ignorance goes very deep, as I have made clear in my questions to this forum) that determining drinking dates must be more of an art than a science, I always aim to drink the wine at what I call its “middle years” i.e. if the window is 2020-2028 I will try to drink the wine during 2024. I thought that that would be a safe bet. If I apply that rule to Joll’s example, I think it still works, even with the changed window.
And all this because one is getting old, and does not want finish a full bottle during a meal. Rats!
Luckily Coravin was invented…


Related but different I see the Bordeaux 22 EP offer has the magnum classic selection in a window 5 years later than the standard size classic collection. The end date is the same.

Curious if there is any formula around.

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I have never, as far as I remember, opened a bottle before the start of its TWS drinking window. On the other hand I have opened many after, sometimes long after, the end of the window, without any problems. So my feeling, which I think is shared by many in this Community, is that the TWS windows tend to be rather conservative, and many wines remain fine long after the window is closed. Of course in this case they are no longer covered by the guarantee.
You surely won’t come to grief aiming for the middle of the window, but it may be worth trying to drink a few a bit earlier, or leave some a bit longer. You might find you prefer your wine a bit younger or a bit older. Or perhaps the middle of the window will suit your taste best.


Very true. Particularly if multiple bottles are involved, in which case drink the first ones in the middle of TWS drinking window then take a view from there.

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Can I offer an alternative reason (or more likely another process working in parallel):

The glass bottle is microscopically porous, full of tiny dents and holes. These pores function like a catalytic converter allowing changes to the wine’s chemistry to take place. Smaller bottles have a greater surface-to-wine proportion and therefore greater/faster change. So the wine devlopes faster in a half bottle.

I of course have no references, and base this theory on heresay.

I believe, though I stand to be corrected, that the difference between the ageing speeds of halves, 750mls, magnums et al stems from the the fact that the cork will admit a certain amount of oxygen per year (roughly, 1mg per year).

For halves, 750mls, and magnums (all of which tend to have the same size cork), this equates to a higher ‘mg of oxygen per ml of wine’ admitted per year the smaller the bottle is, hence the faster ageing. Whilst this should (and, in practice, usually does) hold true for double magnums and above, the calculation for these is thrown off a little as these bigger bottles have bigger, non-standardised (and often hand-cut) corks, meaning that the quantity of oxygen that they admit per year is less certain.

One formula that is often touted about is to multiply the drinking windows of a 750ml bottle by 1.5 for every time that you double the size. So a 750ml of [2020 vintage of insert wine here] which has a drinking window of 2030 - 2045 would have the following windows for a half and magnum respectively:

Half (/1.5): ~2027 - ~2037
Magnum (*1.5): ~2035 - ~2057.

Obviously worth taking with a healthy pinch of salt, and nothing is an exact science, but the ‘1.5x rule’ has, anecdotally at least, tended to correlate reasonably well with state of the halves/bigger bottles that I’ve drunk.

I’ve not heard @lapin_rouge‘s theory re the glass before, but it wouldn’t surprise me if that also played a part.

Thanks for the formula. My brother-in-law who is 10 years older says it not worth him buying anymore decent Bordeaux as he sees no point buying wine for his daughter to enjoy when he has died before the age he likes to drink them at.

With the formula and his preferences it almost seems as even half bottle are not the answer. In his financial position I think I would still buy the odd case in expectation. His daughter appreciates good wine and is currently doing well for herself and now buying wine to store in his cellar. What better item to inherit or enjoy at a memorable family meal if he is holding on to life to try that mature bottle.