Lotus Water Drops

Times have changed: with the advent of the Barista Hustle water recipe and products like Lotus Water Drops, which allow independent adjustment of water hardness and alkalinity, coffee enthusiasts have become much more interested in water customization to improve coffee taste.

In recent months, I've been using Lotus Water Drops at home to brew coffee and better understand the effect of water chemistry on flavor. In this article, I want to tell you about the drops, the standard way to use them, and a quick method I use to discover the ideal water for a particular coffee.

About the drops

A set of LWD contains four dropper bottles:

• Calcium Chloride (CaCl₂)

• Magnesium Chloride (MgCl₂)

• Sodium Bicarbonate (NaHCO₃)

• Potassium Bicarbonate (KHCO₃)

Calcium (Ca) and Magnesium (Mg) contribute to hardness,
while Sodium (Na) and Potassium (K) contribute to alkalinity.

(All values expressed in ppm refer to CaCO₃ equivalent.)

For 450 ml of water:

• 1 drop Ca → +10 ppm hardness

• 1 drop Mg → +10 ppm hardness

• 1 drop Na → +5 ppm alkalinity

• 1 drop K → +5 ppm alkalinity

For 1 gallon of water (≈ 3.78 L):

• 5 drops Ca → +6 ppm hardness

• 5 drops Mg → +6 ppm hardness

• 5 drops Na → +3 ppm alkalinity

• 5 drops K → +3 ppm alkalinity

Basics: Hardness and Alkalinity

Hardness (or GH – General Hardness) measures bivalent ions (with a 2+ positive charge).
Magnesium and calcium are the primary contributors to water hardness, and depending on their levels and proportions – and who you ask 😊 – they can add sweetness, body, or make coffee seem dull.

Alkalinity (or KH – Carbonate Hardness) acts as a buffer to acidity.
Too little alkalinity → coffee can be too acidic and unfinished.
Too much → chalky or flat taste.

The effects of these minerals on taste are not linear or always predictable.
For example, I tested four LWD recipes with the same coffee, and the cups at 10 KH (low) and 70 KH (moderately high) were more "lively" and flavorful than those at 30 KH and 50 KH.
At the extremes (0 KH or 150 KH), the influence on taste becomes more predictable.

I like to have a little sodium in my coffee water because it reduces bitterness.
If you want to mellow the bitter taste of a robusta or dark roast coffee, a little extra sodium can help.
(And if you absolutely have to drink a dark roast robusta, you can joke that "you can pour the whole salt shaker in the cup." 😅)

Alkalinity for filter coffee and espresso

Manually adding minerals to water allows for something impossible with standard systems: independent modification of hardness and alkalinity.

Very hard water is not ideal for coffee, as calcium can deposit as scale when heated, affecting the machine.
However, high alkalinity water can have positive effects on espresso.

Many specialists believe that for filter coffee, a level of 30–40 ppm KH provides a good balance of acidity.
Since alkalinity neutralizes acidity, and filter coffee has a concentration of ~1.2–1.4% TDS, espresso (with ~10% TDS) might require 7–8 times more alkalinity for the same effect.
With LWD or sodium bicarbonate, you can experiment with neutralizing espresso acidity for interesting results.

I don't think espresso with 200–300 ppm KH will become the norm, but the results can be pleasant and instructive.

Protecting machines during experiments

Calcium causes limescale deposits, but magnesium does not.
Therefore, you can test recipes with high hardness and alkalinity by increasing the proportion of magnesium and bicarbonate, without significantly increasing calcium.
To estimate the risk of scaling or corrosion, you can use a dedicated online calculator.

How to use Lotus Water Drops – the standard method

The classic method is to add the drops to distilled water (demineralized).
If you don't have distilled water, reverse osmosis (RO) filtered water is the next option.
However, you can add LWD to any water to increase its hardness or alkalinity.

Examples of standard filter coffee recipes (with distilled water):

Lance Hedrick's Light & Bright Recipe (60 GH, 25 KH)
For 1 liter of distilled/RO water:

• 13 drops Ca

• 11 drops K

For 1 gallon of distilled/RO water:

• 50 drops Ca

• 42 drops K

Rao / Perger Recipe (90 GH, 42 KH)
For 1 liter of distilled/RO water:

• 7 drops Ca

• 13 drops Mg

• 8 drops Na

• 11 drops K

(The Rao/Perger recipe was developed by Dan Eils, my partner and 3D printing expert at Litmus Coffee Labs.)

For 1 gallon of distilled/RO water:

• 25 drops Ca

• 50 drops Mg

• 30 drops Na

• 40 drops K

My Lotus Water Drops trick to discover the ideal water chemistry

I felt overwhelmed by the many possible combinations and wanted a quick way to find out what type of water made the beans in my kitchen shine.
Inspired by chemist Samo Smrke's recent discovery, which showed that minerals added before or after brewing influence taste in the same way, I decided to brew a large quantity of coffee with distilled water, then divide the beverage into several equal portions and add LWD directly to the brewed coffee.

Steps to quickly identify your preferred water chemistry:

1. Brew 900 ml of coffee (multiple pour-overs, a large batch brew, etc.).

2. Stir the coffee well.

3. Pour into 4 cups of 225 ml each.

4. Add different LWD combinations to each cup.

   • Each drop of Ca/Mg adds +20 ppm GH

   • Each drop of Na/K adds +10 ppm KH

5. Stir and taste (ideally, blindly).

Example:

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

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

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

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

Although KH influences acidity levels, the differences between 10 KH and 30 KH can be subtle.
I recommend starting with larger variations – e.g., 10 KH, 50 KH, 100 KH, 150 KH – then fine-tuning GH and KH once you perceive the differences.

Lotus Water Drops for roasters

Any coffee roaster selling outside their city faces a problem:
how to roast beans to suit customers' various water types.

There is no simple answer.
One option would be to adopt a recommended standard chemistry (e.g., the Rao/Perger recipe) and encourage customers to use similar water.
Another option: using LWD to simulate various common water types among customers and adjust the roasting profile accordingly.

LWD is probably the most practical method for recreating the water chemistry used by consumers. 💧☕

*reference: Scott Rao