Building Brew Water
Once you understand that water is most of the cup, the logical next step is to stop hoping your tap is good and build your own to a known target. The recipe is always the same shape: start from near-zero water, distilled or reverse-osmosis (RO), which is a blank slate with almost no TDS, then add back a controlled amount of minerals to hit a chosen GH and KH. This gives perfectly repeatable, competition-grade water anywhere in the world, independent of local supply.
#The Two Building Blocks ⚗️
Remineralization needs a source of hardness (calcium and/or magnesium) and, optionally, a source of alkalinity (bicarbonate) to buffer. The two most common DIY salts:
| Salt | Adds | Role |
|---|---|---|
| Epsom salt (magnesium sulfate, MgSO₄·7H₂O) | Magnesium → GH | Brightness, extraction, fruit |
| Baking soda (sodium bicarbonate, NaHCO₃) | Bicarbonate → KH | Buffering, balance, tames sharpness |
Some recipes add calcium (e.g. calcium chloride or food-grade calcium sulfate/gypsum) for body. The headline rule from the chemistry note holds: keep GH at or above KH so extracting minerals outweigh buffering ones.
#Two Approaches
DIY concentrate method: dissolve your salts into a small, strong "stock" solution, then dose a few millilitres of each concentrate into a litre of RO/distilled. Cheap, precise, infinitely tweakable. Commercial sachets: products like Third Wave Water, Lotus, Aquacode, or Perfect Coffee Water are pre-measured minerals you tip into a fixed volume: zero math, less control. Both start from the same blank RO/distilled base.
#A Worked Example 📐
Here is a classic, widely used Barista Hustle–style two-concentrate recipe targeting a balanced profile near the SCA ideal (~68 ppm GH, ~40 ppm KH). All weights are food-grade salts into distilled or RO water.
Step 1. Make two concentrates (per 1 litre distilled water each):
| Concentrate | Salt | Amount |
|---|---|---|
| Hardness | Epsom salt (MgSO₄·7H₂O) | 2.45 g |
| Buffer | Baking soda (NaHCO₃) | 1.68 g |
Step 2. Build a brewing litre:
| Into 1 L distilled/RO, add | Volume of concentrate |
|---|---|
| Hardness concentrate | 10 mL |
| Buffer concentrate | 10 mL |
Resulting water (approx): GH ≈ 68 ppm, KH ≈ 40 ppm, TDS ≈ 110–150 ppm, squarely in the target box.
Adjust to taste: more hardness concentrate for a brighter, more extractive water that flatters light roasts and juicy acidity; more buffer to soften a sharp, sour cup or to suit darker roasts. Always weigh salts on a precise scale and store concentrates refrigerated.
#Why Bother, and the Caveats ⚠️
Never brew with bare RO or distilled water: its near-zero mineral content extracts poorly and tastes hollow, and some sources note it can leach metals from equipment. It is a base, to be remineralized first.
The payoff is total control and perfect repeatability: the same water, every brew, so when you change grind or ratio you know the water held constant. For brewers who don't want to mix salts, the practical middle ground (good filters and the right bottled water) lives in Filtered, Bottled, and Tap Water.
#Continue Reading
- The SCA Water Standard: the target most recipes aim for
- Water Hardness and Alkalinity: the GH/KH logic behind the salts
- TDS and Mineral Content: verifying your build landed on target
- Filtered, Bottled, and Tap Water: the lower-effort alternatives
- Water for Coffee: back to the water hub