There's been a bunch of discussion in this sub about custom coffee water over the last year or so. I stumbled across such a post and decided to give a hoon myself to see what the fuss was about.

I wrote about it on my blog at The Magic Roast. But before the mods delete this cos I threw in a link to my work, the full review is below. The link is to make sure authorship is clear, not to spam the sub.

TL;DR

• Water makes up ~98% of your coffee
• Minerals like calcium and magnesium affect extraction and taste
• Tap water is usually fine, but varies by region
• Custom water can tweak flavour, but it’s a niche upgrade.
• Most people can level up their coffee game by getting some scales first.

At least 98% of your daily filter coffee or long black is water. We don’t drink coffee, we drink coffee flavoured water. It stands to reason that the quality of the water matters.

The Apax Lab box set has 3 bottles of magic. Each bottle has a different combination of minerals like magnesium chloride, calcium chloride, sodium bicarbonate. Each combination has been designed to bring out a specific flavour note or texture from coffee. For example, the “Jamm” combination should make a cup of coffee richer and sweeter, while the “Lylac” will help to emphasise the floral notes in a coffee.

With the power of magic in your hands, there are two ways to use the concentrates:

1. Make your own brew water from scratch
2. Add drops directly to a brewed cup

Making your own water

Making your own bespoke water is where the most fun is. And it’s super simple.

Take some demineralised water and add the coffee minerals by following a recipe based on the coffee you want to make.

Lovely jubbly.

Demineralised water has 1 part per million (ppm) of minerals in it. Tauranga tap water (where I live) has about 35ppm. The Apax Labs recipe for the ‘washed coffee’ will give you brew water with around 150ppm minerals.

Adding it directly to a brewed coffee

Even easier than making your own water is adding a few drops to a cup you’ve made using regular tap water.

Brew a cup, add a drop, stir and drink.

Can’t get much easier than that.

Does it make a difference?

Yes.

When using custom brew water, the difference is subtle, but noticeable. The coffee is different in all the right ways compared to tap water, but not hugely so. The key difference is around the fringes of taste, things might appear more sweeter, or more balanced.

The results are more noticeable when adding minerals to a brewed cup of joe. It’s sort of like adding salt and pepper to your hot chips.

Does it make it better?

This is a harder question to answer, as ‘better’ is so subjective.

I have been experimenting with two different coffees, using the ‘washed coffee’ water recipe and comparing them to a straight tap water brew.

While they were different, they were both very good. Each version had something in it that I really liked, but I didn’t really prefer one over the other.

I think the minerals really shine is when you add them to brewed coffee. While the changes are more subtle per drop, overall the minerals do allow you to take a bad cup and make it good or, or take a good coffee to great.

Who should use custom water?

I think there are four groups of people who would really benefit from playing with water chemistry:

1. People with tank water or water collected from their roof.
2. People with really awful tap water (looking at you Taranaki).
3. People entering into coffee brewing competitions, like the AeroPress Champs.
4. Coffee geeks.

Who shouldn’t?

You. Tap water is good enough for your daily coffee.

I have a heck of a lot of fun playing with water chemistry, because I fit into the coffee geek camp.

But for 99% of people who brew a coffee every morning, this is superfluous.

What’s the verdict? Is it any good?

• Does water chemistry matter? Yes
• Will most people notice? Probably not.
• Should you try it? If you’re a coffee nerd.
• And if you are a coffee nerd, are the Apax Labs minerals good? Yes.

Are you a coffee geek?

Let me know if you’ve tried custom water. Super keen to hear how other people are using these sorts of nerd tools.