How to make pét-nat at home: a step-by-step guide

The pétillant naturel (or pét-nat, for short) is an excellent way into the world of homemade wine. It avoids several of the risks associated with traditional aging and yields a lively, fresh and often one-of-a-kind wine. This method, called “ancestral,” differs from the traditional method (or Champagne method) mainly in how the bubbles are created: here, you simply let alcoholic fermentation finish in the bottle, whereas the traditional method requires a second fermentation specially triggered to produce the gas. Since reliable, exhaustive resources on making pétillant naturel are rather scarce apart from a few discussions on Reddit, the topic was a natural fit for a blog article.

Pros and cons of making a pét-nat

Before deciding to make wine from your grapes with the ancestral method, a few factors are worth considering:

The pros

• The bubbles will hide certain minor flaws in home winemaking, such as a slight presence of Brettanomyces or volatile acidity;
• Once the wine is bottled, there’s nothing left to do! That’s far less stressful than making a still wine, where many risks remain until the final bottling; and
• The wine will keep bright, lively fruit aromas since it is completely protected from oxidation and reduction.

The cons

• The wine can go in all sorts of directions and there is no way to control that. Once it’s bottled, it’s impossible to predict how it will turn out;
• If a major flaw appears during alcoholic fermentation, it will surely be amplified in the bottle; and
• Depending on when you bottle, there can be too much or too little pressure, and the lees can also be unpleasant when you taste the wine.

Choose and prepare your grapes to succeed at a pét-nat

Not all grapes are suited to making a pétillant naturel, and certainly not at just any stage of ripeness: you have to make an informed choice. To make the assessment easier, I’ve summed up the four key conditions in the diagram below, adapted from this excellent article.

The grape profile to look for

1. Impeccable sanitary condition: Rotten or contaminated grapes can introduce flaws into the must, and once bottled, the wine has a good chance of amplifying those problems.
2. High acidity (pH < 3.5): High acidity will protect the wine during alcoholic fermentation while making the final product much more pleasant to drink.
3. No vegetal flavours: Grapes that aren’t ripe will have vegetal aromas that the wine’s fizz will exacerbate until they possibly become unpleasant.
4. Brix level between 18 and 21: Lower than that and the grape isn’t ripe enough. Higher than that and the resulting high alcohol level will get in the way of the end of fermentation in the bottle.

My suggested winemaking protocol

A winemaking protocol is, in a way, the “recipe” to follow. It lays out all the key decisions to make to get a given style of wine. For a pét-nat-style wine, here is the protocol I recommend and the one I followed for astrofizz:

1. Pick the grapes at 21 degrees Brix while making sure by taste that they have a certain acidity.
2. Destem the entire harvest, then crush it in a container that minimizes the presence of air.
3. Let the skins macerate, ideally cold, for 24 to 48 hours.
4. Press the must and transfer it to a carboy kept at room temperature.
5. Rack halfway through fermentation, that is, at a specific gravity of 1.040.
6. Bottle as soon as the specific gravity is around 1.003.

This protocol is simple and easy to repeat from year to year, while producing a fresh, lively, fruity pétillant naturel.

Measure the specific gravity before bottling: the key to success

Once fermentation is well under way, the next challenge is bottling at the right time. Bottle too early and the bottles will explode or empty themselves on opening because of the accumulated pressure, on top of an unpleasant amount of lees. Bottle too late and the wine may not sparkle at all, because too little gas will have formed during fermentation in the bottle.

How to use a hydrometer properly

The hydrometer is an absolutely essential tool for bottling your pétillant naturel successfully, since it is far more precise than a refractometer. For a successful reading:

1. Fill the graduated cylinder that comes with the hydrometer with fermenting must, stopping a few centimetres before it’s full. The must’s temperature should be around 20°C. If not, you’ll need to correct the reading using an online calculator;
2. Gently insert the hydrometer until it floats on its own. Be careful not to let it drop to the bottom, because it could break;
3. Pinch the top of the hydrometer and spin it like a top to set it rotating. This removes the gas bubbles from active fermentation that could skew the reading; and
4. Note the result, then spin it 2 more times, noting each time. The average of the 3 measurements is the specific gravity of the fermenting must.

Choose the moment to bottle

The ideal window for bottling a pétillant naturel is between 1.000 and 1.006 specific gravity. Typical pétillants naturels have 2 to 3 bar of pressure, making 1.003 the ideal specific gravity for bottling.

At first glance, 1.000 may seem surprising: that value is generally associated with pure water, so with a complete absence of sugar. Yet must isn’t made up only of water: it also contains alcohol (less dense than water) as well as various minerals. The result: even at 1.000, there is on average still between 2 and 6 g/L of residual sugar, which is enough to produce a light fizz. Below 1.000, though, so little sugar remains that the wine will be practically flat.

At 1.007 specific gravity, the project becomes risky, which is why that zone is highlighted in the table. To build the table, I used the rule of thumb that 4 g/L of residual sugar generates 1 bar of pressure in the bottle. Even though a quality bottle can withstand up to 8 bar, certain conditions will let the pressure win out, for example:

• A very small volume of air under the cap (e.g. barely 1 or 2 cm);
• A high temperature (e.g. 30°C or more during a heat wave); or
• A poorly crimped cap (e.g. not enough force applied to the arm of the capper).

Moreover, the more sugar there is at bottling, the more lees the fermentation will produce. Those same lees will have a negative impact on tasting when present in large quantities, forcing a disgorging as a result.

Choosing the bottle, the cap and the equipment

To seal airtight the pressure-rated bottles used for pétillants naturels, you should use 29 mm crown caps. Be careful not to mix them up with 26 mm crown caps, which are meant for beer bottles.

Pressure-rated bottles

In my article on the 7 beginner mistakes I covered the different types of pressure-resistant bottles and how to recognize them. So I’m adding to that by showing below the type of bottle I recycle every year for my cuvées. The one in the photo also weighs 897 grams, which puts it in the sparkling wine bottle category.

Each cap needs its capper

There are two types of capper and, of course, I have a recommendation…

• Bench capper (or lever capper): This is the type to go for, since the lever action applies enough pressure to seal bottles easily. I’d suggest this model, which is identical to mine.
• Hand capper (or pincer capper): Frequently used in the brewing world, many winemaker friends have told me they had bottles that leaked when sealed with this type of capper, since it doesn’t apply enough pressure. Avoid!

Disgorging and pét-nat styles

Disgorging is the act of removing the lees from sparkling wines. Mandatory in the traditional method, it is left to the winemaker’s discretion in the ancestral method. Not removing the lees is also in line with the “non-intervention” philosophy of natural winemakers.

Why, when and how to disgorge

Why disgorge? The first reason is that it removes the lees and so keeps them from accidentally mixing with the wine when it’s consumed. Less waste! The second reason is that it also lowers the pressure. By opening the bottle, about 1 bar of pressure will be lost.

When to disgorge? After fermentation has finished! It’s easy to recognize because the wine will turn translucent and a powdery deposit (the lees) will have formed at the bottom of the bottle. If in doubt, wait: it’s perfectly realistic to disgorge the spring after the harvest.

How to disgorge? I’ve put the procedure together below:

1. Resuspend the lees in the bottles by shaking them, then stand the bottles upside down, vertically. A friend’s tip: use empty crates, the SAQ (Québec’s liquor board) gives them away.
2. Once the lees have settled in the neck of the bottle all the way to the cap, you’ll need to freeze them. To do that, put the crate outside on a cold winter day or put the bottles in your freezer. After 60 minutes, the tip should be frozen but not the wine. It’s time to disgorge!
3. With a manual disgorging tool (or disgorging key; page in French) in hand, make sure you’re wearing clothes you don’t mind ruining and that nobody is nearby. Raise the bottle to 45 degrees pointing up, then pull off the cap with a sharp jerk: the lees, now frozen, will be expelled by the pressure. Finally, put your thumb over the bottle to prevent more wine from escaping.
4. Now stand the bottle fully upright again, add wine to make up for what was lost, then seal it again with the capper. And there you go!

Choosing your pét-nat style

With all this knowledge in hand, the tree of possibilities can look impressive. Which bottle pressure to choose? Disgorge or leave the lees? To guide the decision, here is a reminder of the 3 must-know wine styles in the field:

• Col Fondo: The “original” pétillant naturel from Italy. Contains between 1.0 and 2.5 bar of pressure and is never disgorged;
• Frizzante: The disgorged cousin of Col Fondo; and
• Spumante: Like Frizzante, but with a pressure between 4.0 and 5.0 bar. More often made with the traditional method than the ancestral one.

Spumante is often confused with Prosecco. To tell them apart, remember that the first is a wine style whereas the second is a Denominazione di Origine Controllata (DOC), the Italian equivalent of the French AOC. A DOC combines a geographic region, a subset of grape varieties and rules to follow. Some Spumante can therefore be Prosecco and vice versa.

Still undecided? Try to recreate the style of a wine you’ve loved! Personally, I love rosé Col Fondo, so that’s the style I’m trying to recreate, year after year.