What minerals do I need to make coffee water?

For the simplest recipes, just two: Epsom salt (magnesium sulphate heptahydrate) for hardness and baking soda (sodium bicarbonate, not baking powder) for alkalinity. Some recipes add calcium chloride, magnesium chloride or potassium bicarbonate. Buy food-grade minerals.

Can I use tap water instead of distilled?

Not for these recipes: they assume a mineral-free start. You can, though, blend tap water with distilled water to dilute it, which moves hardness and alkalinity down together. Tap water changes with the seasons, so check it now and then.

Is DIY water safe for espresso machines?

Filter-coffee recipes aren't designed with boilers in mind. Third Wave Water sells a separate espresso profile to avoid scale, and research published by the SCA suggests espresso water should keep hardness low while allowing more alkalinity. Check your machine maker's water advice first.

How long does homemade coffee water keep?

Keep it in the fridge. Jonathan Gagné of Coffee ad Astra finds a gallon of distilled water turns bad after about a week out of the fridge, or a month in it, and suggests smelling it before use.

DIY Coffee Water Recipes: Epsom Salt and Baking Soda

Q: Is Third Wave Water the same thing?

It's a ready-made version: a stick of minerals you add to a gallon of distilled or reverse-osmosis water, in profiles for light, medium and dark roasts, cold brew and espresso machines. The company doesn't publish the exact amounts.

DIY coffee water means starting from distilled water, which has no minerals at all, and adding back just the ones that help coffee: magnesium or calcium for hardness and bicarbonate for alkalinity. It sounds fussy, but the simplest recipes need only Epsom salt, baking soda and a scale. This page gives the method and the best-known recipes, as collected by Jonathan Gagné on his Coffee ad Astra blog.

The short version

Start with distilled water, which is mineral-free.
Epsom salt adds hardness; baking soda adds alkalinity.
Make a concentrate: minerals plus distilled water to 200 g.
Dose 4 g of concentrate per litre of distilled water (16 g per 4 litres).
Aim for the SCA’s targets: hardness 50–175 ppm, alkalinity near 40–70 ppm.

What do you need?

Item	Why
Distilled water	A mineral-free base
Epsom salt (MgSO4·7H2O)	Magnesium, for hardness
Baking soda (NaHCO3), not baking powder	Bicarbonate, for alkalinity
A scale reading to 0.1 g or better	The amounts are small
A glass jar holding about 250 ml	For the concentrate; avoid metal

Source: Coffee ad Astra. Some recipes also use calcium chloride, magnesium chloride or potassium bicarbonate. Buy food-grade minerals, not lab or pharmacy grade, Gagné advises, and keep opened bags airtight. Epsom salt is the heptahydrate form; if your chlorides come in a different hydrate, the weights change.

How do you make coffee water?

Gagné’s method, which all the recipes below use:

Weigh the minerals for your recipe into a glass jar.
Add distilled water until the total weighs 200 g. This is your concentrate.
Let it degas. Leave it a few hours in a cool, dark place with the lid loose, stirring now and then. Warm water speeds this up.
Dose it: add 16 g of concentrate to 4 litres of distilled water, or 4 g per litre.
Shake the concentrate before each use. Some white deposit is normal and disappears once diluted.

One 200 g concentrate makes 50 litres of brewing water. Keep it, and the finished water, in the fridge.

Which recipes can you make?

These all make a 200 g concentrate, dosed at 4 g per litre:

Recipe	Epsom salt	Baking soda	Other minerals
Melbourne	2.9 g	1.0 g
World of Coffee Budapest	6.2 g	3.4 g
Barista Hustle simplified SCA	8.4 g	3.4 g
Barista Hustle	9.8 g	3.4 g
Matt Perger	10 g	3.4 g
Barista Hustle simplified Hendon	12.2 g	2.6 g
Barista Hustle Hard	15.4 g	2.9 g
Rao/Perger	5 g	1.7 g	2 g magnesium chloride hexahydrate, 2 g calcium chloride dihydrate, 2 g potassium bicarbonate
Dan Eils			5 g magnesium chloride hexahydrate, 5 g calcium chloride dihydrate, 5 g potassium bicarbonate

Source: Coffee ad Astra, citing Scott Rao, Matt Perger and Barista Hustle. The two-ingredient recipes run from soft (Melbourne) to hard (Barista Hustle Hard); more Epsom salt means harder water.

In Gagné’s blind tastings the Rao/Perger recipe came first, for a bright, well-balanced cup, with Dan Eils second. He found Third Wave Water’s classic profile very good for little effort, but preferred Rao/Perger. He hadn’t tasted most of the two-ingredient recipes when he published them.

Which recipe should you start with?

If you want two ingredients, start in the middle of the table, with the Barista Hustle simplified SCA or Matt Perger recipe, then move up or down by taste. If you can buy the chlorides, try Rao/Perger. Measure the result with an aquarium test kit for hardness and alkalinity if you want to check it against the SCA water standard.

Can you adjust water for espresso?

Yes, and you may need to. Espresso uses roughly a tenth as much water per gram of coffee as filter, so water with more alkalinity has less effect on the shot’s acidity, Marco Wellinger writes in the SCA’s 25 Magazine. Hard water, though, scales up a machine. Research he describes suggests espresso water can sit as low as 20 ppm hardness with up to 150 ppm alkalinity. A softening cartridge, which lowers hardness but not alkalinity, is the easiest way to get there.

What about ready-made minerals?

Third Wave Water sells mineral sticks: one stick per gallon of distilled or reverse-osmosis water, in profiles for light, medium and dark roasts, low acid, cold brew and espresso machines. It doesn’t publish exact amounts; it says its blends contain no chlorides and don’t build up limescale. Gagné measured the classic profile’s alkalinity at about 43 ppm, close to the SCA’s range.

Water and other guides

The SCA water standard: the targets these recipes aim for.
Water hardness for coffee: what’s in your tap water now.
Coffee grind size chart: dial in once your water is right.

DIY Coffee Water Recipes

How do I make my own water for coffee?