Why Your Homemade Sparkling Water Goes Flat: The Science of Fizz

It’s a common and frustrating experience. You invest in a sparkling water maker, like the SodaStream Jet, eager for fresh, on-demand seltzer. You follow the instructions, press the button, and hear the satisfying “buzz.” But when you take a sip, the result is disappointing.

As one user, Christopher, described the experience: “the fizz fails to stay… It took me to give it around 10-12 pumps to have fizz… no matter how many pumps i give the bottle the fizz just does not stay.”

This is not a faulty machine. It is a failure to follow the laws of physics.

A home soda maker is a desktop physics laboratory. To get a good result, you must understand the two scientific principles it relies on: Henry’s Law and Carbonic Acid.

The “Fizzics”: Why Pressure Needs Cold

The entire “magic” of a soda maker is based on Henry’s Law, a principle of physical chemistry. The law states that the amount of a gas (CO2) that can be dissolved in a liquid (water) is directly proportional to the pressure of that gas above the liquid. * The CO2 cylinder contains gas under high pressure. * Pressing the button on the machine releases that high-pressure gas into the sealed bottle. * This pressure forces the CO2 molecules to dissolve into the water, creating a supersaturated solution.

But there is a catch: Gases are more soluble in cold liquids.

This is the #1 mistake users make. If your water is room-temperature, the molecules are moving too vigorously. They won’t “hold on” to the CO2. * Warm Water: Fails to dissolve the CO2 properly. You press the button 10 times, wasting gas, and the fizz escapes almost immediately. * Ice-Cold Water: The molecules are less energetic, creating a stable environment that can trap and hold far more CO2. This creates a dense, sharp carbonation that lasts.

Your machine isn’t broken; your water isn’t cold enough.

The “Bite”: Why You Must Flavor After

The second common mistake is adding flavor before carbonating. This has two bad outcomes, as noted by users. First, “when added [flavors] the fizz is not as strong.” Second, “carbonating a soda after you’ve already flavored it can end up making a huge mess.”

This is a problem of chemistry. The “bite” of seltzer comes from Carbonic Acid (H2CO3), which forms when CO2 reacts with plain water.

The syrups, fruit drops, or juices contain sugars, citric acid, and other “impurities.” These impurities get in the way of the CO2-water reaction. More importantly, they provide thousands of nucleation points—tiny, microscopic sites for the CO2 to form bubbles.

When you add flavor first, you are encouraging the CO2 to “bubble up” and escape the water, rather than dissolve into it. This wastes gas, kills the fizz, and creates the “huge mess” (a volcano of foam) as all the gas escapes at once.

The correct (and only) method is to:
1. Carbonate plain, ice-cold water first.
2. Then, slowly add your flavors (like the included fruit drops, fresh lemon, or “Apfelschorle”—a mix of juice and sparkling water popular in Germany).

The Machine: A “Razor Blade” Model

You must also understand the tool. The SodaStream Jet is a simple, non-electric machine. It’s an effective “convenience” tool, not a “lifetime purchase.”

Users note that its build can feel “flimsy” and that critical components, like the valve mechanism, are “plastic, not metal.” This is part of its “razor and blades” business model. The machine (the “razor”) is sold at a reasonable price, but you are locked into its ecosystem of proprietary CO2 cylinders (the “blades”). This is where the real cost lies.

Furthermore, this specific model does not have the features of older or higher-end units. As one user noted, “my last unit would make a ‘burping’ sound when it was fully carbonated… This unit does not make that sound.” You, the user, must decide how many “pumps” (typically 3-5 for a sharp fizz) are enough.

Conclusion:
Your soda maker is not magic. It’s a simple, manual tool that obeys the laws of physics. If your fizz is failing, the solution is simple: Use ice-cold water, and add your flavors after you carbonate.