Cocktail Queries is a Paste series that examines and answers basic, common questions that drinkers may have about mixed drinks, cocktails and spirits. Check out every entry in the series to date.
Making your first forays into the world of mixed drinks, you’re bound to come across varieties of carbonated water sooner rather than later. They’re essential in the world of mixology for infusing a sparkling, effervescent quality to drinks with names like “fizz” or “spritzer,” being used in a variety of situations when something like sparkling wine just wouldn’t taste right. They tend to be light and unobtrusive, perfect as a background element to “lengthen” a drink and reduce its ABV, but can also be flavored to fit a particular cocktail profile. Learning to stock the right varieties of carbonated water in your home bar is basically a “day one” lesson of any aspiring home bartender.
But they can also be a bit confusing. Is “club soda” really a different product than seltzer? Or sparkling mineral water? And what exactly makes “tonic” so different? Here’s a simple guide to what each of the terms implies.
Tonic is the most unique and distinctive of carbonated waters, and by far the easiest to identify from taste alone. It is sparkling water that has been infused with both minerals and quinine, a powder isolated from the ground bark of the cinchona tree. Quinine has a distinctly bitter, mineral flavor, which is balanced in almost all commercial tonic waters by added sugars or sweeteners. This gives tonic water a balance between bitterness, somewhat resinous notes and corresponding sweetness, which pairs very well with liquor such as gin in the ubiquitous G&T. Tonic waters may contain genuine sugars, while “diet” or zero calorie versions use the same sweeteners present in commercial soft drinks. Several varieties of commercial tonic syrups are also produced, which allow a drinker to customize their preferred level of quinine flavor.
Tonic water was invented by British naval officials in early 19th century India, who used quinine powder as an anti-malarial, but found the bitter taste difficult to swallow in purely powdered form. The powder was subsequently combined with carbonated water, with added sugar, to create tonic water. Gin was presumably introduced into the equation shortly thereafter, creating one of the world’s most enduringly popular mixed drinks. Modern tonic, it should be noted, is much milder and less intense as far as the bitter quinine is concerned than the historical version.
The word “seltzer” implies pure, carbonated water with no additional additives or minerals. For decades, that’s what the term largely meant to consumers—a pure form of carbonated water—although the modern boom of flavored seltzers (La Croix and co.) that have gained popularity as replacements for sugary soda, not to mention hard seltzers, have given the term a new connotation.
In its base form, however, traditional seltzer water (such as La Croix Pure) is simply water + bubbles, and that’s it. This can make it a good choice in mixology when only carbonation is desired, but it’s arguably less commonly used for this purpose than club soda (which we’ll talk about next).
However, the ready availability of so many different flavored seltzers gives drinkers a wide range of ways to infuse new flavors into their drinks without worrying about additional sugars or calories. For example, a grapefruit seltzer water can be swapped into a paloma recipe for the traditional grapefruit soda, creating a lighter and crisper version of that tequila-based drink. In the end, it’s just a matter of taste.
Club soda may seem like the same thing as pure seltzer water at first glance, but this is water that has been enhanced by the manufacturer with additional minerals. As in seltzer, it is infused with CO2, but club soda is also commonly infused with minerals such as potassium sulfate, disodium phosphate, sodium bicarbonate and sodium chloride.
That last one, sodium chloride, is better known as good old-fashioned table salt. That doesn’t make these “salt water” by any means; nor will they taste noticeably salty to most palates. Rather, the minerals simply round out the flavors of these waters and are intended to give a little boost to the flavor profile of the drinks they’re mixed into. That makes club soda the go-to for many bartenders when it comes to adding bubbles in mixed drinks or cocktails, and the expected addition for classic mixed drinks of highballs like the scotch ‘n soda.
If you see “soda” as an ingredient in a cocktail recipe, they’re talking about club soda. Could you substitute seltzer? Sure, but the results may be slightly more flat in terms of flavor, depending on your own palate as much as anything.
Finally, we have sparkling mineral water, a category that is very similar to club soda, with one major difference: The minerals here aren’t being added by the manufacturer. Rather, mineral water by U.S. definition is water with mineral content that originates at the source—which is to say, the body of water already contains these minerals from the ground. This includes popular sparkling mineral water brands such as Perrier and San Pellegrino. As with seltzer, some of these brands are likewise available in flavored variations, which have their own cocktail applications.
In its base, “pure” form, however, sparkling mineral waters can often be expected to have a slightly more unique flavor than most club sodas, owing to their relatively higher levels of mineral content. Flavors will vary from brand to brand, depending on the source of each water, and many of these brands also tend to feature higher levels of average carbonation, which can make them distinctive. You may want to experiment with several brands of sparkling mineral water to see which one suits your palate best.
Jim Vorel is a Paste staff writer and resident liquor geek. You can follow him on Twitter for more drink writing.