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Sparkling Wine: Bubbles, Pressure and Sweetness

Sparkling wine being enjoyed
Sparkling wine being enjoyed
If bubbles are wrong, who wants to be right?

A Crib Sheet for the Strange Stuff

Sparkling wines are wonderful! In fact, I’d be drinking them every day, except that would leave less capacity for me to be drinking everything else that I also happen to enjoy.

When I use the word “sparkling”, I am referring to wines with bubbles – all of them, no matter what the source, methodology or quality. The reason I’m mentioning this is because the EU has a specific definition for which wines are “sparkling”: only bubbly wines above a certain (rather high) level of pressure in the bottle. If I followed their logic, I would have to use the word “effervescent” instead of “sparkling”. I don’t care for that too much. For me – and for many others – “sparkling” is the best catchall for the category.

This post offers a brief guide for three sometimes confusing issues concerning sparkling wines:

  1. the different ways a wine can be made sparkling
  2. what the various levels of pressure in the bottle mean
  3. the way sweetness is classified

Bringing out the Bubbles

The bubbles in your wine are carbon dioxide. The source of those bubbles is almost always as a by-product of alcoholic fermentation. The only exception to this is in the case of carbonation.

There are five commonly encountered methods used to get those bubbles into your bubbly. The most important of these all use the addition of yeast and sugar to a finished, still wine in order to bring about a second fermentation.

Pour it.

Bubbles from Secondary Fermentation

  • Traditional Method – the wine undergoes a second fermentation in the bottle in which the wine is then later sold, and usually involves a longer period of contact with the yeast, which can add complexity to the wine. Production is more labour and cost-intensive. All the most expensive sparkling wines are made this way.
  • Transfer Method – the same as the traditional method, above, except that the wine is removed from the bottle after the second fermentation, filtered, and then rebottled – all under pressure to minimise the loss of bubbles. This is most often done to fill large and small format bottles that are not practical or economical to produce directly.
  • Tank/Charmat/Martinotti Method – the secondary fermentation takes place in a tank, with bottling done under pressure to minimise loss of bubbles. The wines can be produced with or without extended yeast contact. The method is called “Martinotti” by the Italians, after the Italian scientist who patented the process in 1895. “Charmat” is the name most often used to refer to the method, however, because the French enologist Eugène Charmat was the inventor who patented the pressurised tank in 1907 that allowed Martinotti’s method to be commercially viable.

Bubbles from Primary Fermentation

  • Méthode Ancestrale (Pet-Nat) – the base wine is put into bottles before it is finished fermenting, and then sealed – often under crown cap, these days. Sometimes they are filtered, most of the time they are not. Currently “Pet-Nat” (Pétillant Naturel) is all the rage, particularly with the “natural” wine crowd. Since they continue to ferment and are seldom filtered, these wines can vary significantly from bottle to bottle. They never arrive at the kind of pressure in bottle that those using secondary fermentation can reach. But the diversity and unpredictability is all part of the charm, apparently. This is the “original” method for creating a sparkling wine, already mentioned in France in the 16th

Other Bubbles

  • Carbonation – this is just what you think it is: CO2 is added to the wine in the same way that it is added to any soft drink or sparkling water. Bubbles are large, aggressive, and dissipate quickly. The cheapest way to make a wine sparkling, and only used for the cheapest wines.

The Pressure

There are many words used to describe a sparkling wine in Italian or in French – heck, even in German and English, if you are paying attention. Many of them indicate how high the pressure in the bottle will be.

So who cares? What does the amount of pressure n the bottle do? Well, many people find that sparkling wines with lower pressure feel creamier and smoother on the palate than the ones with higher pressure. This is one of the reasons why the “Satèn” version of Italy’s Franciacorta (a traditional method sparkling wine) is made to slightly less pressure than the normal bottlings. The wines can only be labelled as Satèn if they are less than 5 bar, instead of the normal 6 – 6.5 bar.

Although it may not seem overly important, there are some reasons why some sparkling wines have more pressure than others. It has mostly to do with the method in which they have been made, with “traditional method” wines having the highest pressure – and requiring much heavier, stronger bottles to cope with it – and “méthode ancestrale” often having some of the lowest pressure in the bottle.

There are two broad categories of wine depending on the amount of pressure in the bottle, those above three atmospheres (3 bar) of pressure, and those below. Fully sparkling wines tend to have 5 or 6 bars of pressure – which is really very high, when you consider that a car tire tends to settle in between 2 and 3 bar.

Most sparkling wines are simply known by their appellation: Champagne, Cava, Franciacorta, Deutsche Sekt, etc. There are some words to look for, however, that will generally indicate the level of pressure inside the bottle. Please note, however, that not all of these terms are legally defined to indicate a specific pressure. I present these as a rough guide.

Pressure above 3 bar: Sparkling Wine, Crémant and Mousseaux (French), Spumante (Italian), Schaumwein or Sekt (German)

Pressure below 2.5 bar: Semi-Sparkling, Pétillant (French), Frizzante (Italian), Perlwein (German)


And now, the most bizarre of the three topics: how different levels of sweetness are labelled and understood.

Almost all the sparkling wines using secondary fermentation also make use of a fluid mixture of sugar, yeast and nutrients in order to bring about the second fermentation. This fluid is usually carefully balanced to achieve the level of alcohol desired for the finished wine. It has very little to do with the final sweetness; the yeasts will ferment all of the sugar into alcohol. The sweetness of the final wine is generally adjusted at bottling, through the addition of sugar dissolved in a still wine of the same quality. This dosage will change the level of sweetness of the resulting wine – anywhere from 0 g/L to … well, the sky is the limit.

Recently, the trend has been towards more and more wines with so-called “Zero Dosage”, which is to say that the wine is completely dry. In my opinion, these wines can be the most interesting and fulfilling, but they can also be very hard to get right. A little bit of residual sugar can go a long way to making a simple sparkling wine more enjoyable to drink.

In any case, the different levels of sweetness – and the range of residual sugar that they indicate – are as follows:

Sugar Level (g/L)             Term

0-2 or 3                               Brut Nature

0-6                                       Extra Brut

Up to 12                             Brut

12-17                                  Extra-Sec/Extra Dry

17-32                                  Sec/Dry/Secco/Trocken

33-50                                  Demi-Sec/Medium Dry/Abboccato/Halbtrocken

Over 50                              Doux/Sweet

Time for a glass of bubbly!

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