Homemade Tonic water syrup

When I (Matt) was a kid, I wanted to grow up to be a mad scientist. You read that right. Not a regular scientist, mind, but specifically a mad scientist. I grew up on a diet of black-and-white movie serials — such as Buck Rogers and King of the Rocket Men — bafflingly broadcast on Saturday morning BBC children’s TV schedules in the late 1970s and early 80s and each containing a resident mad scientist. There was something about the role that appealed. Was it the bubbling bunsen burners? The rakish lab coat? The crazy hair? Whatever the allure, I determined that that would be my life career.

Most Christmases, I’d receive a chemistry set which I would fall upon with an evil cackle and a twirl of my non-existent mustache. But although I did dip my toe briefly into a chemistry career, that wasn’t to be my life path. And yet, I’ve never lost that love of throwing a bunch of chemicals together to make something fantastic, and of course I still occasionally sport the crazy hair. And after all, what is cooking but another form of chemistry?

So today I’d like you to join us in the lab as we giggle madly and whip up a batch of homemade tonic (or more accurately, Tonic Syrup, to be mixed with club soda and your spirit of choice). Our version is based on a recipe that was first developed by mixologist Kevin Ludwig, which then went through a veritable hot-potato game of variations by several talented cocktail enthusiasts including Jeffrey Morganthaler, Jennifer McLagan and David Lebowitz.

The basic recipe (which is both simple and delicious), contains quinine (cinchona bark), citric acid, limes and lemongrass. But Nerds gotta nerd, so we made a few additions which we feel add depth and complexity. The end result is, in our minds, the perfect mix of sour, sweet, bitter and floral.

Is tonic water really a tonic?

The active ingredient in tonic water is the bitter chemical quinine, found in cinchona bark. Cinchona itself is a genus of plants growing primarily around the Andes in South America, and its bark has been used historically to treat malaria and other fevers. The British in colonial India were the first to combine the bitter tonic with gin to make it more palatable. (Note: you can combine most things with gin to make them more palatable.) Nowadays, commercial tonic water still uses quinine as a flavoring, but at quantities much too low for medicinal purposes. So you can claim that gin-and-tonic for health reasons if you like, but battling malaria is unlikely to be one of its benefits.

Most commercial tonics, even the fancy ones, lean heavily into sweetness, often with a slight citrusy tang and a mild bitter finish. It’s tasty stuff, but we wanted something with a little more punch (and without the high-fructose corn syrup and preservatives like sodium benzoate). You’ll notice that our version is not clear. In fact, we used blood oranges to add a beautiful blush to the the color. If you want a lighter colored tonic, stick with lemons and limes, instead of the mix of citrus we used.

This version of homemade tonic is effectively a concentrate, mixed at pouring time with club soda to dilute it and add effervescence. FDA regulations prevent us from claiming that it’s healthier, but we like to think, at least, that it’s a more authentic flavored mixer than the commercial variety.

Tonic Ingredients and FLAVOR NOTES

The key bitter flavoring in tonic is the cinchona bark discussed above. We found cinchona at Amazon (the 8oz bag will serve for at least 8 batches of this recipe) but you may have a good local source such as a drinks supply store. You’ll also need powdered citric acid. Citric acid is the same acid found in lemon juice, but it’s concentrated and shelf-stable, which helps to balance out the sweetness and helps the tonic last longer in the refrigerator (it will keep for months, if you can make it last that long).

We should note that you by no means have to include every single ingredient in your version, but each adds a flavor note that we enjoyed. Instead of just the traditional limes, we added a mix of citrus (blood orange, pink grapefruit, lemon and lime). Blood orange was mostly for its gorgeous color, so feel free to sub regular oranges. We wanted some warm, spicy flavors, so we added star anise, black pepper, and allspice. For herbal and floral notes, a little fresh rosemary, green cardamom and dried lavender. Of course, it wouldn’t be tonic without lemongrass and quinine (cinchona bark). You should be able to find most of the ingredients in a regular grocery store or asian market and, of course, the internet is your friend when it comes to the harder-to-source elements.

The recipe is very customizable and you could absolutely make it with just cinchona, lemongrass, and citric acid. So if you don’t have some of these ingredients, it’s okay! Your tonic will still be delicious. Feel free to play with any other flavors you have in your pantry — try fresh thyme or sage from the herb garden; juniper berries, coriander or fennel seed or bay leaf from the spice rack.

crafting your homemade Tonic

NOTE: Make sure you use a non-reactive saucepan as this is a very acidic mixture (So stainless steel, glass, or glazed ceramic is what you want. Avoid aluminum, un-lined copper and iron cookware). 

Once you have your ingredients assembled and prepared, the process is simple. Use a sharp vegetable peeler to remove the rind of all the fruit (you can also use a microplane zester to grate it if you like). Add all the peels to a pot filled with one quart of cold water. Juice the fruit and add that as well (don’t worry about pits, it will all get filtered). You should end up with about 1 cup of juice in total. NOTE: If you use only lemons and/or limes, reduce juice to 3/4 of a cup to prevent the mix from being too tart. 

Add all the rest of the ingredients (except for the sugar syrup) and bring it to a boil. Lower the heat to a simmer, cover, but leave it a little ajar so steam can escape. Let it simmer for 15 minutes, then turn off the heat, uncover it, and let it cool to room temperature. Pour the liquid and all the flavorings into a glass container with a sealable lid and refrigerate it for a couple of days. Give the jar a shake once or twice a day to get the most out of the infusion.

Next, make the sugar syrup by adding the sugar and water to a small saucepan and heat it, stirring occasionally, until it fully dissolves. Allow it to cool to room temperature. NOTE: You can make the sugar syrup up to a week in advance and keep it chilled in the refrigerator in a sealed container. You won’t need to use it until the tonic is ready to strain.

When the infusion is ready, place a mesh strainer over a large bowl and pour the tonic through it. Discard the solids. Then line the strainer with several layers of cheese cloth (you can also use a clean tea towel or coffee filters) and slowly pour the liquid through, back into the pot. If using the tea towel or filters, you will need to have some patience because it will drain quite slowly. Once the tonic is filtered, stir in the sugar syrup (if your syrup is very cold, straight from the refrigerator, it will take a bit of stirring to combine). Taste the tonic and adjust the sweetness, if desired. Transfer the tonic into clean glass bottles or jars, and refrigerate until you’re ready to use it.

Homemade tonic syrup will keep for several months in the refrigerator (though open the jars every so often to allow any trapped gasses to escape).

HOW TO USE homemade TONIC WATER SYRUP

Find our recipe below for a Gin (or Vodka) Tonic, and enjoy it as a refreshing chilled summer drink. Garnish it with a citrus wedge and a sprig of rosemary if you want. If you like a sweeter drink, add a little more syrup, until it tastes right to you.

If you’re feeling cheeky, try using bourbon instead. It tastes like a delicious and complex Old Fashioned. We loved it. The syrup is also flavorful and balanced enough that it makes a delicious mocktail, no spirits needed.

You can also use this concentrate as a flavoring for Gin-and-Tonic Pound Cake! You’ll find that recipe in Cork and Knife, our guide for cooking with alcohol.

Whether you’re a mad scientist, a normal scientist, or just someone who likes mixing stuff together in the kitchen, this is a great homemade tonic recipe and we hope you have fun with it. Cheers!