Sparkling water is made by dissolving carbon dioxide gas into still water under pressure. The basic principle is simple: when CO₂ is forced into water at high pressure, the gas dissolves into the liquid. When you open the bottle and release that pressure, the dissolved gas escapes as the familiar fizzy bubbles. This process works the same way whether it happens in a massive factory or a countertop machine, though the scale and precision differ considerably.
The Physics Behind Carbonation
Carbonation relies on a principle called Henry’s Law: the amount of gas that dissolves in a liquid is directly proportional to the pressure of that gas above the liquid. Push more CO₂ against the water’s surface, and more of it dissolves. Release the pressure, and the gas comes back out. That’s why an unopened bottle of sparkling water looks perfectly clear, but the moment you twist the cap, bubbles start forming and rising.
Temperature matters just as much as pressure. Cold water holds significantly more dissolved gas than warm water. This is why a warm can of sparkling water erupts more violently when opened: the gas that was barely staying dissolved escapes all at once. It’s also why manufacturers chill water before carbonating it, and why your sparkling water tastes fizzier straight from the fridge.
How Factories Carbonate Water
Industrial sparkling water production follows a consistent sequence designed to maximize carbonation and keep it locked in until you open the bottle.
First, the water is purified and chilled to near-freezing temperatures. Cold water absorbs CO₂ more efficiently, so this step is essential for getting a strong, lasting fizz. The chilled water then moves into a carbonator, a sealed vessel where CO₂ is injected under controlled pressure and temperature. The gas is typically pushed through a device called a carbonation stone, a porous surface that breaks the CO₂ into tiny bubbles, dramatically increasing the surface area where gas meets water and speeding up dissolution.
Once the water reaches the target carbonation level, it moves to the filling line. This is where things get tricky. If the carbonated water were simply poured into bottles at normal atmospheric pressure, the CO₂ would immediately start escaping. Instead, bottling lines use counter-pressure (or isobaric) filling technology: the bottle is first pressurized to match the pressure of the carbonated water, then filled, then immediately sealed. This keeps the fizz intact from the carbonator all the way to the cap. After sealing, bottles are packaged in conditions that minimize exposure to heat, light, and oxygen, all of which degrade carbonation over time.
How Much Fizz Goes In
Carbonation levels are measured in “volumes of CO₂,” which refers to how many volumes of gas (at standard pressure) are dissolved in one volume of liquid. Different beverages target different levels. Sparkling water generally falls in the range of 2.5 to 3.5 volumes. For comparison, highly carbonated sodas like Coke and Pepsi are carbonated to 3.5 to 4 volumes, which is why they feel more aggressively fizzy on your tongue.
The pressure needed to achieve these levels depends on temperature. To carbonate water to about 5 volumes of CO₂ at 5°C (41°F), for example, a University of Florida guide calculates a starting pressure of roughly 38 PSI. Lower carbonation targets need less pressure. Home carbonation machines typically operate at lower pressures and produce a lighter fizz than commercial systems, though multiple presses of the button can push carbonation higher.
Naturally Sparkling Water
Not all sparkling water gets its fizz from a machine. Naturally sparkling water comes from underground springs where the water absorbs CO₂ from volcanic activity or carbonate-rich rock formations deep below the surface. Brands like Perrier and San Pellegrino source from these springs. The FDA defines “sparkling bottled water” as water that, after any treatment, contains the same amount of CO₂ it had when it emerged from the source. In other words, the carbonation has to come from the earth, not a factory tank.
Naturally sparkling water also tends to carry dissolved minerals picked up during its underground journey. To be labeled “mineral water” in the United States, it must contain at least 250 parts per million of total dissolved solids and come from a geologically protected underground source. No minerals can be added after the fact. If TDS falls below 500 ppm, the label must say “low mineral content.” Above 1,500 ppm, it must say “high mineral content.” These minerals, things like calcium, magnesium, and bicarbonates, give naturally sparkling water its distinctive taste, which varies noticeably from brand to brand.
Sparkling Water vs. Club Soda vs. Seltzer
These three drinks are all carbonated water, but they’re not identical. Seltzer is the simplest: plain water plus CO₂, nothing else. It’s the closest thing to homemade sparkling water and has a clean, neutral taste.
Club soda starts the same way but includes added minerals and salts, typically sodium bicarbonate and potassium sulfate. These additions give club soda a slightly salty, mineral-y flavor and a subtly different mouthfeel. The minerals are added during production rather than occurring naturally.
Sparkling mineral water, as described above, gets both its carbonation and its mineral content from the source itself. The flavor profile depends entirely on the geology of wherever the spring is located. Tonic water is a different category entirely: it contains sugar (or sweetener) and quinine, making it closer to a soft drink than to sparkling water.
Making Sparkling Water at Home
Home carbonation machines like SodaStream work on exactly the same principles as industrial systems, just at a smaller scale. A pressurized canister of food-grade CO₂ connects to the machine. You fill a bottle with cold water, attach it, and press a button to inject CO₂. The gas enters the water under pressure, dissolves, and you have sparkling water.
A few things make a noticeable difference in the result. Start with the coldest water you can, ideally refrigerated for several hours. Cold water absorbs and retains more CO₂. Give the bottle a gentle swirl after carbonating to help distribute the gas evenly. And carbonate plain water only, then add flavoring afterward. Sugary or acidic liquids foam unpredictably under pressure and can make a mess or damage the machine.
Each CO₂ canister typically carbonates 40 to 60 liters of water, depending on how fizzy you like it. More button presses per bottle means stronger carbonation but fewer total bottles per canister. If your sparkling water tastes flat compared to store-bought, you likely need either colder water or more CO₂.