When it comes to carbonation, temperature makes all the difference.
When we recently evaluated home seltzer makers, we noticed that the instructions for all of the models recommend starting with cold water rather than room temperature or warm water. Curious about this guideline, we tried carbonating water at 32 degrees, 68 degrees, and 140 degrees. The results surprised us. The 32-degree water turned out incredibly effervescent, with small, long-lasting bubbles, while the 140-degree water was barely carbonated. The 68-degree sample sat right in the middle of these two extremes. A review of some scientific literature confirmed our observations: Water at 32 degrees can hold five times more carbon dioxide than water at 140 degrees.
Why the drastic difference? Unlike solids, which become more soluble as the temperature of a liquid increases (for example, it’s much easier to dissolve sugar in hot liquids than in cold), gas is harder to incorporate into warmer liquids. That’s because when gas gets warm it expands and dissipates, so there is less of it available to be dissolved in liquid. So for the fizziest homemade sodas and seltzer, always use ice-cold water.