By Alexander J. Pandell, Ph.D.

There’s a dangerous trend in restaurant Champagne service—serving Champagne at cellar temperature, about 55-60°F, instead of cold, 35-38°F.

I’ve come across this practice at several well-known restaurants in Chicago, San Francisco and New York. To properly serve Champagne, one must thoroughly chill it before popping the cork to insure the maximum amount of carbon dioxide (CO2 or “the bubbles”) is retained by the beverage as opening a bottle that is at 55°F results in rapid loss of carbon dioxide and flat Champagne. The essence of Champagne are the bubbles. To lose most of the carbon dioxide by opening a bottle that’s not properly chilled is to defeat what Champagne is. Once opened it’s too late to chill the bottle because there’s very little carbon dioxide remaining!

The Chemistry. There are two factors that affect how much carbon dioxide dissolves in wine. First, the pressure of the carbon dioxide gas above the wine. The greater the pressure of carbon dioxide above the wine, the more carbon dioxide dissolves in the wine and the more bubbles are released when you drink the Champagne. This is Henry’s Law, which states that the solubility of a gas in a liquid is proportional to the pressure of the gas over the solution. The normal partial pressure of carbon dioxide in a bottle of Champagne is 4 to 6 atmospheres or 60-90 pounds per square inch (psi). This very high pressure is why champagne bottles are made of thick glass and have a cork that is wired down. The second factor is the temperature of the wine. The colder the wine, the more carbon dioxide dissolves in the wine.

What happens when a “warm” (48-60°F or higher) bottle of Champagne is opened? As soon as the cork is removed, the “pop” you hear is the carbon dioxide saying “good-bye sucker” and you have flat champagne. The partial pressure of the carbon dioxide drops from 6 atmospheres (90 psi) to 0.0003 atmospheres (0.0045 psi), reducing the solubility of carbon dioxide in the wine by a factor of 20,000 compared to what it was in the corked bottle, resulting in rapid loss of what carbon dioxide remains.

Here’s what happens when a cold bottle of Champagne is uncorked. (Cold refers to 35-38°F, which is the typical refrigerator temperature.) The partial pressure of carbon dioxide drops as before, but a significant amount of carbon dioxide remains dissolved in the wine because it is much more soluble in cold than warm Champagne. Voila! We have a steady stream of bubbles in our glass of Champagne as we partake in the consumption of this beautiful elixir of life!

What’s the best way to cool Champagne? Immerse the bottle (up to its neck) in a water-ice bath—a mixture of water and ice at 32°F– for at least 30 minutes. Placing the bottle in the refrigerator 24 hours prior to serving is also acceptable and a lot more practical. When I order Champagne at a restaurant, I have the server place it in an ice bucket with a slushy mixture of ice and water for 20 minutes before popping the cork to be sure the contents are cold. Once opened the bottle should be kept immersed in an ice bucket, not just placed on top of the ice.