Years ago, the main concerns about water for coffee were “don’t scale up your espresso machine,” “don’t make coffee with very hard water,” and “don’t use water that tastes or smells bad.” Times have changed; since the advent of the Barista Hustle water recipe and products like Lotus Water Drops, capable of independently manipulating water hardness and alkalinity, coffee enthusiasts have become much more interested in customizing water to enhance coffee flavor. 

Over the past few months I’ve been using Lotus Water Drops at home to make coffee and to learn more about the effect of water chemistry on coffee flavor. In this post I’d like to tell you about the drops, the standard way to use them, and a shortcut I use to discover the optimal water for a particular coffee.

About the drops

A kit of LWD contains four dropper bottles:

• Calcium Chloride (CaCl2)

• Magnesium Chloride (MgCl2)

• Sodium Bicarbonate (NaHCO3)

• Potassium Bicarbonate (KHCO3)

The Calcium (Ca) and Magnesium (Mg) contribute to hardness

The Sodium (Na) and Potassium (K) Bicarbonate contribute to alkalinity

(All references to ppm in this post refer to ppm as CaCO3 equivalent.)

For 450 ml of water:

• 1 drop Ca  adds  10 ppm hardness 

• 1 drop Mg adds  10 ppm hardness

• 1 drop Na  adds  5 ppm alkalinity

• 1 drop K  adds  5 ppm alkalinity

For one gallon of water:

• 5 drops Ca   adds  6 ppm hardness

• 5 drops Mg  adds  6 ppm hardness

• 5 drops Na adds 3 ppm alkalinity

• 5 drops K adds 3 ppm alkalinity 

Hardness and Alkalinity basics 

Hardness, also known as General Hardness (GH), is a measure of divalent ions (ions with a positive charge of 2+). Magnesium and Calcium make up the bulk of hardness in water, and, depending on their levels and ratios – and who you ask :0 – may add “sweetness,” “structure,” or flatness to coffee. 

Alkalinity, also known as Carbonate Hardness (KH), buffers acidity. Too little alkalinity, and coffee may taste acidic and unrefined. Too much, and coffee may taste chalky or flat. 

Note that the flavor effects of these minerals are not “linear” or always predictable. For example, I recently tested four LWD recipes using the same coffee, and the cups at 10 KH (low) and 70 KH (moderately high) “popped” and tasted better than the cups at 30 KH and 50 KH. At extremes, such as 0 KH or 150 KH, the effect of KH on flavor is more predictable. 

I prefer a little sodium in my coffee water because sodium counteracts bitterness. If you want to tame a bitter coffee such as a robusta or dark roast, adding extra sodium may help. If for some reason you must drink a dark-roast robusta, just dump an entire salt shaker in the mug after brewing. 

Alkalinity for filter coffee and espresso

When adding minerals to water, one can do something not usually possible with standard water-treatment systems: easily and radically change hardness or alkalinity independently of the other. Very hard water is not great for coffee making because some of the hardness will precipitate as scale upon heating the water, and scale can damage coffee machines. However, very high-alkalinity water can have positive effects espresso. 

Many coffee professionals agree that when making filter coffee, water alkalinity levels around 30–40 ppm yield reasonable levels of acidity. Given that alkalinity neutralizes acidity, and filter-coffee strength is approximately 1.2–1.4% TDS, to neutralize acidity in espresso at a strength of 10% TDS requires water with perhaps 7–8 times more alkalinity. With LWD or a jar of sodium bicarbonate, one can experiment with neutralizing espresso acidity for interesting effect. I doubt making espresso with KH of 200-300 ppm will become the norm, but I have found the results enjoyable and insightful. 

Protecting your machines while experimenting

Calcium can create scale but Magnesium cannot. Therefore, you can test high-hardness and high-alkalinity recipes by increasing Magnesium and bicarbonate without increasing Calcium beyond a certain level. To estimate the scaling and corrosion potential of a recipe, you can use this online calculator.

How to use Lotus Water Drops - the standard method

The traditional way to use LWD is to add drops to distilled (demineralized) water. If distilled water is not an option for you, reverse-osmosis water is the next best option, but one can add LWD to any water to increase its hardness or alkalinity. 

A couple of standard filter-coffee recipes based on distilled would look like this: 

Lance Hedrick’s Light & Bright recipe (60 GH, 25 KH)

To one liter of distilled or RO water, add: 

13 drops Ca

11 drops K

To one gallon of distilled or RO water, add: 

50 drops Ca

42 drops K

Rao / Perger recipe* (90 GH 42 KH)

To one liter of distilled or RO water, add: 

7 drops Ca

13 drops Mg 

8 drops Na

11 drops K

*the Rao/Perger recipe is the brainchild of Dan Eils, my partner and 3D printing expert at Litmus Coffee Labs

To one gallon of distilled or RO water, add: 

25 drops Ca

50 drops Mg 

30 drops Na

40 drops K

My Lotus Water Drops hack to reverse engineer your preferred water chemistry

Recently I was frustrated by the myriad possible water chemistries and decided to create a shortcut to finding what water chemistry would make the beans in my kitchen taste best. Using a surprising recent insight from chemist Samo Smrke that coffee tastes the same whether water minerals are added before or after brewing, I decided to brew a large amount of coffee using distilled water, split the brew into several equal portions, and add LWD to the brewed coffee. 

Here is a shortcut to zero in on your preferred water chemistry: 

1. Brew 900ml of coffee (you can do this by combining multiple pourovers, using one giant immersion, or whatever is convenient.)

2. Stir the brewed coffee well.

3. Pour equal 225ml portions into four cups.

4. Add a different combination of LWD to each cup. Each drop of Ca and Mg will add 20 ppm GH; each drop of Na and K will add 10 ppm KH)

5. Stir and taste (preferably blindly)

For example, I tried this recently to zero in on my preferred KH level for a coffee: 

• Cup one: 1 Ca + 2 Mg + 1 Na           (60 GH, 10 KH)

• Cup two: 1 Ca + 2 Mg + 2 Na + 1 K (60 GH, 30 KH)

• Cup one: 1 Ca + 2 Mg + 3 Na + 2 K (60 GH, 50 KH)

• Cup one: 1 Ca + 2 Mg + 4 Na + 3 K (60 GH, 70 KH)

Note that while KH drives acidity level, you may not sense a difference between levels as close as 10 KH and 30 KH. I recommend beginning with much larger differences, such as 10 KH, 50 KH, 100 KH, and 150 KH. Once the differences are apparent, you can challenge yourself with smaller variations in GH and KH. 

Lotus Water Drops for roasters

Any roasting company that sells coffee outside of its home city faces a dilemma: how to roast coffee to suit the variety of water chemistries its clients use. There is no easy answer to this. One option would be, of course to use a common/recommended water chemistry (such as the Rao/Perger recipe above) and to encourage customers to use similar water. Another option would be to use LWD to mimic a variety of common water chemistries customers are likely to use, and to roast in a way that yields good results for that spectrum of chemistries. LWD is probably the most convenient way to mimic customers’ water chemistries. 

Click HERE to for more information and to purchase Lotus Water Drops