DIY Tonic Water: Use It for Personalized Gin and Tonics All Summer Long

Memorial Day may not fall on the solstice, but it still signifies the beginning of the summer season. With it comes a bounty of fruits and vegetables, picnics, and plenty of afternoons spent grilling outdoors. And even if our Bay Area summer days come interspersed with plenty of cloudy ones, we can still celebrate like the rest of them. The best way to do so? Switch your drinking habits over from dark spirits to light, refreshing gin, served with bubbly, refreshing homemade tonic water.

If you take a look at a bottle of Schweppes tonic, you’ll likely see three ingredients: water, corn syrup, and quinine. It’s easy to do better than that at home. Start with the quinine. Most commercial tonic manufacturers use chemically-produced clear quinine in their tonic water, but the bitter flavor originally comes from the ground bark of cinchona trees. Today, cinchona bark is sold as a natural herbal remedy and can be found through most online and brick-and-mortar herb shops. It’ll turn homemade tonic water a golden brown color, but otherwise has the same effect as the commercial variety. To offset the bitter flavor of the cinchona, we’ll add cane sugar (instead of corn syrup) as well as citric acid and the complementary flavors of citrus and lemongrass.

The easiest way to make carbonated tonic water at home is to first make a sweetened tonic concentrate. This viscous liquid will keep in the fridge for an extended period of time and it can be diluted with as much seltzer water as you’d like upon serving.

Most of the recipes for tonic water I found online called for simmering the aromatic mixture in water for close to half an hour. This method makes a tonic concentrate that is extremely bitter, blunt, and intense. I found that I liked tonic that was “cold-extracted” much better -- the flavor of the citrus really shines. Plus, it’s also a tiny bit easier!

To begin, gather one orange, lemon, and lime. I like to use organic citrus here because we’ll be using the zest. If you can’t stomach the cost of organic limes right now, be sure to scrub the exterior very well. Use a vegetable peeler to remove the zest in large swaths, leaving as much of the white pith behind as possible. Transfer the zest to a 1-quart glass jar. Halve the peeled citrus and squeeze the juice into the jar. I like to use a levered hand-juicer to make sure I get out as much juice from the fruit as possible.

Next, chop the lemongrass. Remove the first outer layer or two until you reach an unblemished layer. Trim off the really fibrous top 6 or 8 inches of the lemongrass, as well as the bottom 1 inch or so of root. Discard. Cut the remaining lemongrass into rough chunks, about 1/2 inch long. Add these to the jar with the citrus.

Cinchona bark is sold “cut” or in powder form. I like to use cut bark because it has a clean flavor and it is easier to strain out of the mixture than the powdered form. You’ll find that the bark pieces are sold in various sizes, so it is best to weigh out the bark instead of using a volume measurement. I like to use one ounce, which (using my cinchona bark) measures out to around 1/4 cup. Add this to the jar as well.

If you have a favorite flavor of gin that you’re planning on drinking with the tonic, you can consider adding spices to pair with its botanicals. For example, if you like a juniper-forward gin such as Aviation, you could add a few juniper berries to the jar. Or perhaps up the citrus flavor of the tonic by adding coriander seeds. Allspice and cardamom are also common additions. Personally, I like to keep the tonic a blank slate in order to use it with a wide variety of gins, so I don’t add anything else in the way of flavorings.

Once you’ve got all the flavor elements in the jar, cover the mix with 2 1/2 cups of water. Close the jar, give it a shake, and place it in the fridge. Forget about it for three days.

At some point over those 72 hours, make concentrated simple syrup. This extra-thick syrup will be used to sweeten and thicken the tonic concentrate. Heat 3 cups natural cane sugar (I like its richer flavor, but feel free to use regular granulated instead) and 1 1/2 cups water in a medium saucepan over medium-high heat. Once the mixture comes to a simmer, reduce the heat and stir gently until all of the sugar dissolves. If you’re using natural sugar, the syrup will be brown. That’s okay.

Remove the syrup from the heat and whisk in 1/4 cup citric acid. This tart powder is used as both a preservative and a flavoring agent for the tonic. It adds a bit of pucker to the final concentrate. Also add a big pinch of kosher salt to balance the flavor. The citric acid and salt should dissolve easily in the syrup with a few good whisks. Transfer the syrup to another 1-quart glass jar, let it cool to room temperature, and then refrigerate until the cinchona mixture is ready.

At the end of the steeping period, taste a small spoonful of the cinchona mixture. It should be bitter, of course, but should also taste of citrus and lemongrass. If you think the flavor is weak, you can let it steep a little longer in the fridge. Be careful though -- you don’t want it to be too bitter. If you like the flavor, it’s time to strain.

I like to use a fine-mesh strainer lined with coffee filters to ensure that I get out every last bit of cinchona residue from the tonic. Help the straining along by wetting the coffee filters before adding the cinchona mixture. You’ll probably need to add the mixture in batches, unless you have an extra-large strainer. It will take several minutes for all of the mixture to seep through the filters. Be patient.

Once everything is strained, discard the solids. Pull out the citric acid-filled simple syrup and add it to the cinchona mixture in stages. Since we’re adding the syrup last, you can control how sweet you’d like the final tonic to be. Add all of the syrup for an extra sweet tonic, or hang back a little for a dryer result. Taste as you go, keeping in mind that you will be diluting the concentrate with seltzer water for serving. I added about 2 cups of simple syrup, bringing the total amount of concentrate to 4 cups. Give everything a good whisk to ensure that the sugar is well distributed in the cinchona mixture.

At this point, the tonic concentrate is ready to go. You can serve it right away or transfer it back to a (clean) 1-quart glass jar and refrigerate for up to two months. To serve, you’ll want to add seltzer water. I have a home soda maker, but you can also use store-bought seltzer or club soda to dilute. I like to use equal parts tonic concentrate and seltzer, but if you’d like a more subtle drink, you can dilute further to a 2:1 ratio of water to tonic. If you’re making just one drink, you can mix it right in a highball glass. (It’s pretty.) Otherwise, mix the tonic and soda up in a pitcher before serving. To make a gin and tonic, start with 1 to 2 ounces of gin in a highball glass filled with ice. Top with tonic water and a lime wedge.

Recipe: DIY Tonic Water

Makes 4 to 5 cups, enough for 8 to 16 cups tonic water
Note: Cinchona bark and citric acid are available online at Mountain Rose Herbs or at Lhasa Karnak Herb Company in Berkeley.

Ingredients:

• 1 orange
• 1 lemon
• 1 lime
• 4 cups water
• 1 stalk lemongrass, chopped coarse
• 1/4 cup (1 ounce) cut cinchona bark
• 1–2 tablespoons additional herbs and spices, such as allspice, cardamom, or juniper (optional)
• 3 cups natural cane sugar
• 1/4 cup citric acid
• 1/8 teaspoon kosher salt

Equipment:

• Vegetable peeler
• Cooking scale
• 2 (1-quart) glass jars with tight fitting lids
• Medium saucepan
• Fine-mesh strainer
• Coffee filters
• Whisk

Instructions:

1. Remove the zest in large strips from orange, lemon, and lime (leaving the white pith behind), then halve and juice fruits. Combine the zests, juice, 2 1/2 cups water, lemongrass, and cinchona bark in a 1-quart glass jar. Refrigerate until the flavors have melded, about three days.
2. Meanwhile, make simple syrup by combining the remaining 1 1/2 cups water with the sugar in a medium saucepan. Bring mixture up to a simmer over medium-low heat until the sugar has dissolved. Remove the saucepan from the heat and whisk in the citric acid and salt. Let cool to room temperature and refrigerate until the cinchona mixture has finished steeping.
3. After 72 hours, strain the cinchona mixture through a coffee filter-lined fine-mesh strainer into a large bowl. Rinse out glass jar.
4. Whisk simple syrup into the cinchona mixture until thoroughly combined. Transfer tonic concentrate back to glass jar and store in the refrigerator for up to two months.
5. To dilute and serve, combine tonic concentrate with plain seltzer water at anywhere from a 1:1 to 2:1 ratio of water to tonic. For a gin and tonic, combine tonic water with ice and 2 ounces gin in a highball glass. Serve with a lime wedge.