Blog : coffee water

Water and Chemistry

Water and Chemistry

This article was originally written by Matt Campbell for the membership of Coffee Props.  Please visit www.coffeeprops.com to join the conversation and be a part of the community!

So much focus has been put on the coffee itself, and rightfully so. The grind size, consistency of grind, freshness and quality of the bean, roast quality and method of brewing are all important factors when considering the end result of your brew. Traditionally when we would talk about water we would be discussing water to coffee ratio, temperature of brew water, speed and type of infusion method, and filtration. While these factors are all important, recent studies have broadened our understanding of our water.

 

What can be so complicated? Water is H2O, right? Well, yes; and no, not always. Without getting too deep into the physics and chemistry of it all, water is made up of hydrogen and oxygen atoms, and the liquid we all know and love is capable of dissolving all sorts of other molecules. The makeup of water depends on a multitude of factors and conditions, and it is a complex array of chemistry and physics. Each water sample can react differently with its surrounding environment, and it is no different when we heat it and pour it over a bed of coffee.

 

It has been shown that magnesium (Mg +2) and calcium (Ca +2) are important to extracting flavor from coffee. These two atoms readily dissolve in water to create ions. These ions have a charge, which reacts chemically with flavor in the coffee to extract it into solution. Adding the sum of these two minerals together to calculate their abundance in parts-per-million (PPM) will give us an idea of general hardness, or GH.

 

On the opposing side of these ions are carbonate ions (HCO3 -1), which is more commonly referred to as the alkalinity or buffering agent (KH). This also contributes to coffee flavor, but it must be kept in check to prevent undesirable changes.

 

Although there are other minerals and ions in solution, the three mentioned above are the most important factors that impact flavor. These ions must be kept at the right level of hardness, but they must also be in proper quantities relative to each other. The preferred ration seems to be 2:1 in favor of the general hardness when the GH is around 100 ppm.

 

Believe it or not, that was actually a pretty dumbed down version of the whole story. Although these are just the basic facts, there is a whole textbook of information called, “Water for Coffee.” If you are they type that needs to know more, there is no more relevant and thorough information available. It isn’t exactly an easy read, but it is articulate and complete.

 

All this fantastic information has been made available recently, but now what can we do with it? Sure, we can purchase titration test kits and expensive filtration solutions to make the perfect water for coffee, but for the average household this is not a feasible option. Is all lost?

 

Not quite. The chemistry may be complicated to understand, but some very smart people have broken it down for us. Matthew Perger, WBC all-star and coffee guru has been dropping knowledge for us, so I will yield the floor to his recipe for perfect water:

 

Water Recipe:

 

Based on instructions from Matthew Perger, and the book Water for Coffee

Ingredients: Sodium Bicarbonate (aka baking soda); magnesium sulfate (Epsom salt); distilled water

NOTES:

  • Distilled water, spring water, and purified water are not the same. It must be labeled distilled for this to work.
  • The Epsom salts must be unscented, and read magnesium sulfate. MgSO4

 

INSTRUCTIONS:

 

To make concentrate:

  1. Add 8.6g baking soda, and 25g Epsom salt to 500g distilled water. This is your concentrate.
  2. Shake this concentrate until it is all dissolved.

 

To make perfect coffee water:

  1. Place 500g of distilled water into a clean glass container.
  2. Carefully mix 2.5g of CONCENTRATE into the distilled water.