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Homemade Tonic Water Filtration

Today's post was written by Kevin Liu. We were having an email conversation about filtration- he uses a small-pore coffee filter that removes the bark bits when he makes tonic water and I thought that filter might also be good for removing charcaol after clarifying spirits- and I asked him if he'd share his information with us.

Kevin Liu is an editor at ScienceFare.org, a site about cooking with science. Kevin is obsessed with cocktails and science and he's always looking for new geeky ways to get drunk.  You should email him at  kevin@sciencefare.org. 

Take it away, Kevin!

Up until recently, cocktail geeks had few options for good tonic water.  The mass-market stuff uses high-fructose corn syrup, quinine extract, and citric acid and lacks both nuance and depth.  To make a really classy gin and tonic meant DIY-ing your own tonic water. As it would turn out, quinine is a controlled substance in the United States because in large doses it can heart problems, headaches, nausea, and birth defects, to name a few.

Let's not forget that quinine was first prescribed as a treatment for malaria and that gin was used to make it more palatable.  The stuff's no joke, and for that reason, quinine extract (the stuff used in commercial tonic) is not available for purchase.

To make your own tonic, you have to go to the source - Peruvian tree bark, or cinchona.  There are a number of places you can order the stuff from online.  I picked up a pound of it from the Pennsylvania Herb Company for about $30 shipped.  That's pretty steep from some bark, but a pound is a whole lot of tree - just 'sayin.  If you consider a four-pack of "gourmet" tonic water runs about $6... the economic benefits start to become apparent.

The big problem home tonic-makers often run into is filtration.  Powdered cinchona is almost impossible to filter out and the cut-up bark (which is what I used) inevitably contains some powdered material as well.  Cheesecloth and fine-mesh filters won't catch the particles and coffee filters clog quickly.

So I hacked some stuff together. I found a website that talks about really small pore-size (1 micron) filters for coffee.  The guy basically bought a polyester filter bag, cut rounds out of it, and jerry-rigged it into an aeropress coffee maker.  Why shouldn't the same thing work for filtering out cocktail stuff?  ...and it does!


Aeropress Coffee Maker

In the original article, the poster recommends substituting the polyester round for the standard paper filter - he files down parts of the aeropress to make it fit.  I didn't want to do this, so I just cut the polyester round slightly smaller than the paper filter and used the two in conjunction.  


Filter image by Kevin Liu
Filter image by Kevin Liu

The 1-micron filter caught the cinchona bark beautifully; at the end, the filter was a mass of brown gunk and my tonic syrup came out a lovely transparent, sediment-free brown.

The recipe I used was pretty simple - at this point, I just wanted to see if the aeropress could be used with this method as a proof of concept.  With this initial success, I'm planning to move on to more experiments with other flavors, plant materials, and filtration methods.


Filtered Homemade Tonic Water by Kevin Liu



Combine 20g cut cinchona bark with 1 cup water.  Heat to a boil, then simmer for 20 minutes.  The liquid should reduce/absorb into the bark such that you'll have about a 1/2 cup left.

Strain the liquid first through a fine-mesh metal strainer, then use the aeropress method described above.

Add between 110g and 220g sugar to the cinchona water.  Optionally, add water until you have 2 cups of product to make a 1:4 ratio syrup.

Recipe Notes

I used 220g of sugar to 20g bark and felt that the result was not bitter enough.  With that being said, tonic water desperately needs citric acid for balance (no, lemon juice won't cut it).  Since I didn't want to add any additional flavors to this batch, I really don't know how the ratios will work out in a completed tonic water.  The next steps will be to start adding lemongrass, citrus peels, citric acid, and allspice.  

But I will say that the tonic syrup as described above, 1:4 with soda water, makes a pleasant and sweet gin and tonic.  It goes best with an easy-drinking gin, like New Amsterdam.  A hefty squeeze of lime or lemon gives a nice balance.


Thanks Kevin for sharing your experiments! Has anyone else tried this method or something similar?

Note: Coincidentally, Jacob Grier shared his tonic recipe using a different espresso maker today.