How to Prepare Coffee Brewing Water? How to Use Baking Soda and Magnesium Sulfate in Coffee? Why Can't Espresso Machines Use Tap Water?

The Role of Water in Coffee Brewing

In the coffee-making process, colorless and tasteless water serves as the solvent! Coffee extraction requires it to bring out the flavor compounds hidden within the coffee beans. The deeper you delve into coffee brewing, the more you realize the importance of water.

We often see statements online like: "It's best not to use tap water for making espresso." This isn't because tap water isn't clean enough, but because it contains excessive trace elements. When water is boiled, these substances adhere to the kettle walls, forming scale that significantly affects both the coffee machine's operation and the coffee's taste. This importance extends beyond just espresso brewing—for pour-over coffee, water source selection is equally crucial! As FrontStreet Coffee often mentions, different water sources contain varying amounts of minerals. The presence of appropriate minerals helps extract coffee flavor compounds, while excessive minerals hinder this extraction, resulting in less-than-ideal coffee flavor. Therefore, when brewing coffee, we generally use soft water with lower PPM.

Understanding Water Quality for Coffee

What is soft water? Let's first explain what PPM is! PPM stands for Parts Per Million, a concentration unit representing the mass of solute per million parts of total solution mass. Generally, water quality is expressed in mg/L, which converts to 1ppm = 1mg/L. We can simply understand it as: the more trace elements in water, the higher the PPM. According to the World Health Organization's "Guidelines for Drinking-Water Quality," water with PPM above 200 can be called hard water, while below 200 PPM is soft water. Although most city tap water has PPM below 200, falling within the soft water range, for coffee brewing, the definition of soft water can be even more stringent! When PPM exceeds 140, the water becomes quite saturated, making it difficult to fully extract compounds from coffee! Even with all other parameters appropriate, under-extraction or over-extraction can easily occur. Therefore, tap water is generally not recommended for brewing coffee (unless properly filtered).

Optimizing Water for Coffee Brewing

To address coffee water needs, most people install filtration systems for their tap water to ensure excellent water quality. Of course, if you want to extract even more exceptional coffee flavors, you can also create your own brewing water like competition participants. The simplest method, as mentioned in FrontStreet Coffee's previous article, is to purchase water concentrate for mixing! Simply mix an appropriate amount of pure water (like Nongfu Spring or similar) with one packet of water concentrate and stir well. The only drawback is that it's slightly expensive.

There's also a more down-to-earth method, though it's more complicated to execute because you need to prepare: edible baking soda, edible Epsom salt (magnesium sulfate), and 3 bottles of 1L pure water (using 1-liter containers makes calculations easier). Epsom salt can be difficult to find offline, so it's best to purchase it online. The steps are as follows:

1. First, pour 1.68g of baking soda into one liter of pure water and stir well to dissolve! This creates a 1000ppm solution—our prepared "buffer solution" or "HCO3-." The buffer solution helps prevent pH changes in the solution. Since it has no obvious characteristics, we need to mark it for identification and set it aside for later use.
2. Next, take the second liter of pure water and add 2.45g of Epsom salt, stirring thoroughly to dissolve completely! This creates a "magnesium concentrate" solution containing magnesium ions. It's approximately 1000ppm—remember to mark it and set aside.
3. Finally, we can prepare the brewing water. Here we'll use the water quality requirements range proposed by SCA, with a total hardness range of 120-130ppm. Therefore, we add 40ml of buffer solution, 80ml of "magnesium solution," and 880ml of deionized water to complete our brewing water preparation.

The Impact on Coffee Flavor

FrontStreet Coffee brewed a pot of Ethiopian Kochere using both prepared water and Nongfu Spring water, and the results confirmed our expectations—there were significant differences between the two brews: The Kochere brewed with Nongfu Spring had bright lemon acidity, subtle white floral notes, and a black tea finish~ While the Kochere brewed with prepared water had fuller, rounder acidity and more pronounced floral characteristics!

So, there truly are differences between different types of water! We must not underestimate this ubiquitous liquid—the amount of substances it contains directly affects the taste of the coffee we brew!

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