What on Earth Is a Colmatore?
Updated: Oct 7
The wonderfully simple little device that helps keep a wine vessel full. And the wine protected from too much air.
Walk into an old Italian wine cellar and, among the barrels, demijohns, hoses and mysterious bits of equipment, you may spot something rather curious.
A small glass contraption sitting on top of a vessel, perhaps partly filled with wine.
It looks vaguely scientific. Perhaps a little like an old-fashioned laboratory instrument. Or something you might use to feed a particularly demanding houseplant.
This is a colmatore.
And despite its rather modest appearance, it has a very important job.
It helps keep the vessel properly topped up, gives the winemaker a visible indication of the wine level and, depending on the design and how it is being used, can also allow fermentation gases to escape while limiting the entry of air.
And when you're ageing wine, that's an important bit of housekeeping. Too much exposure to oxygen can lead to oxidation and encourage the growth of acetic acid bacteria, which is how your carefully ageing wine can start heading in the decidedly unwelcome direction of vinegar.
For such a simple little piece of equipment, the colmatore does a remarkably useful job.
First, where did the wine go?
Wine doesn't necessarily stay at exactly the same level while it is ageing.
This is particularly noticeable when wine is kept in wooden barrels. Wood is porous, and tiny amounts of liquid and vapour can pass through it. Over time, some of the wine is therefore lost through evaporation. Changes in cellar temperature can also affect the volume of the wine, and there may be other small losses during normal cellar work.
So a barrel that was completely full when the wine went into it may, some time later, no longer be completely full.
Over a long period of ageing in wood, the cumulative loss can be surprisingly significant, although exactly how much depends on the barrel, the cellar conditions and the length of ageing.
This evaporation is rather poetically known as the angels' share.
Unfortunately, nature doesn't leave that newly created space empty.
It fills it with air.
The space between the surface of the wine and the top of the vessel is generally called ullage. And as that space increases, so does the wine's potential exposure to oxygen.
Which brings us to one of those small but very important jobs in the traditional wine cellar:
colmatura.
Or, quite simply, topping up.
Colmare: fill it up!
The Italian verb colmare means to fill something right up; to fill a space that has become empty.
And that's exactly what happens during colmatura.
As the level of wine in a barrel falls, more wine is added to bring it back up again.
It's an extremely simple idea.
Wine disappears → space appears → add more wine.
The cellar worker therefore needs to keep checking the barrels and topping them up when necessary.
But wouldn't it be useful if there were a little device that could help with this?
Enter the colmatore.
So how does a colmatore work?
A colmatore is fitted into the opening at the top of the vessel — the cocchiume — with its lower tube extending into the wine.
The colmatore itself holds a small reserve of wine. As the level in the vessel drops, wine from the colmatore can compensate for that loss, helping to keep the vessel full. At the same time, because the colmatore is traditionally made from glass, the winemaker has a visible indication of what is happening to the level below.
It's beautifully low-tech.
No electricity.
No computer.
No app telling you that Barrel Number 17 would like some attention.
Just a clever little physical solution to a very old winemaking problem.
If the level changes noticeably, something is happening down below.
But why are we so worried about a little air?
Because wine and oxygen have a complicated relationship.
We often hear that oxygen is the enemy of wine.
That's not entirely true.
Oxygen can play an important role in winemaking and ageing. A wine ageing in a wooden barrel isn't hermetically sealed away from the world. Very small and controlled interactions with oxygen can influence tannins, colour, aromas and the way the wine develops.
But there is an enormous difference between controlled oxygen exposure and leaving a substantial pocket of air sitting above the wine.
Once you have significant headspace, you have a much greater reservoir of oxygen available to interact with the wine.
And too much oxygen can lead to unwanted oxidation.
Fresh fruit aromas can fade. Colours can change. The wine can lose freshness and eventually develop oxidative aromas and flavours that the winemaker never intended.
There is also another potential problem.
A poorly protected surface can create favourable conditions for unwanted microorganisms.
So the objective isn't necessarily:
NO OXYGEN EVER!
It's much more nuanced than that.
It's about controlling how much, when and why.
Which, frankly, describes quite a lot of winemaking.
Is a colmatore the same as an airlock?
Not exactly — although the confusion is understandable.
Some colmatori can also perform the job of an airlock, particularly when fermentation is still producing gas. But that's not the whole story.
A fermentation airlock is primarily designed to allow gases — particularly carbon dioxide — to escape while limiting the entry of outside air.
A colmatore has another important job: colmatura. It helps the winemaker monitor the wine level and keep the vessel properly topped up.
So there is some overlap between the two, but colmatore tells us something that “airlock” doesn't:
it helps colmare.
It helps keep the vessel full.
Of course, modern wineries have other tricks
Today, winemakers have many more ways of protecting wine.
Stainless-steel tanks can be designed to minimise headspace. Variable-capacity tanks can use floating lids. Inert gases such as nitrogen or argon can be used to protect wine from oxygen during certain winery operations.
Temperature can be controlled far more precisely.
And the winemaker has an extraordinary range of equipment available for moving, storing and protecting wine.
But the fundamental problem hasn't changed.
If wine disappears from a vessel, something has to take its place.
And if that something is air, the winemaker needs to understand what that means for the wine.
Which is why I rather love the colmatore.
It's such a wonderfully visible reminder of a problem that modern technology can sometimes make almost invisible.
And then Tuscany comes along and breaks the rules
Because just when you think you've learned the lesson...
Keep the vessel full! Protect the wine from air! Avoid excessive oxidation!
...along comes Vin Santo.
Traditional Tuscan Vin Santo is aged for years in small barrels called caratelli, often under conditions that would make anyone who has just read the previous sections of this article slightly nervous.
The barrels may not remain completely full.
Temperature fluctuates.
Oxidative development traditionally forms part of the character of many Vin Santo styles.
And somehow, through this long, slow and rather mysterious ageing process, something extraordinary can emerge.
Does that mean oxygen suddenly isn't a problem?
No.
It means the desired result is different.
And this is one of the things I love most about wine.
For almost every rule you learn, there is a wine somewhere that seems determined to demonstrate why the real answer is:
Dipende.
It depends.
Legend has it that Leonardo da Vinci invented the Colmatore
If you spend enough time visiting wineries in Tuscany, sooner or later someone will point to a colmatore and tell you another rather wonderful piece of information:
“It was invented by Leonardo da Vinci.”
I've heard this story SOOO many times.
And I would absolutely love it to be true.
Leonardo certainly had an interest in vines, wine and winemaking. He grew up around Vinci, in the Tuscan countryside (and since 2026 its own Chianti subregion), and wine was very much part of the agricultural world he knew. There are also writings associated with him that touch on viticulture and wine production.
So the idea of Leonardo turning his attention to a clever little device for the wine cellar doesn't sound completely far-fetched.
And let's face it: Leonardo da Vinci inventing a glass contraption to help protect Tuscan wine is a story almost too good not to believe.
There is just one small problem.
I can't find convincing historical evidence that he actually invented the colmatore.
The attribution is repeated surprisingly often by wineries, museums and wine publications. But repeating a story isn't quite the same thing as documenting it.
I have yet to find a drawing in Leonardo's notebooks that clearly depicts the familiar glass colmatore, or a contemporary document that describes him inventing one.
What I can find comes considerably later.
By the late 1800s, colmatori were clearly part of Italian wine-cellar equipment. Historical catalogues from 1880, 1887 and 1889–90 provide documentary evidence of glass colmatori from this period.
Of course, that doesn't tell us exactly when the colmatore was invented.
Nor does it prove that something similar wasn't being used centuries earlier.
But there is quite a historical gap between Leonardo's death in 1519 and the documentary evidence I've been able to find.
So until somebody produces a Leonardo drawing, manuscript or other convincing contemporary evidence linking him to the colmatore, I'm keeping this one firmly in the:
Tuscan Cellar Legend
column.
A wonderful story?
Absolutely.
Proven history?
Not quite yet.
And perhaps that's okay.
After all, a little mystery never hurt a Tuscan wine cellar.
A tiny piece of cellar wisdom
The colmatore isn't a spectacular piece of winemaking technology.
It doesn't analyse anything.
It doesn't control temperature.
It doesn't have flashing lights.
It simply sits there, quietly helping the winemaker solve one of the oldest problems of ageing wine:
How do I keep this vessel full?
And perhaps that's why I find it so charming.
Because wine isn't a static substance.
We sometimes imagine that once wine has finished fermenting and has been put into a barrel, it simply sits there ageing peacefully until the winemaker decides it's ready.
But wine is constantly changing.
It reacts.
It evolves.
It evaporates.
Its environment changes.
And somebody has to keep an eye on it.
Sometimes with sophisticated modern cellar equipment.
And sometimes with a small glass object that has been doing the job perfectly well for generations.
Sometimes the cleverest technology in the cellar doesn't need electricity.
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