How to get the best from your coffee - Water Chemistry

I recently published my first book as an ebook, and figured I would start writing a series of blog posts to dig into more details as well as discuss some of the things that I talk about in it.

Just so you know, I will be doing limited printings soon as well. I personally love the feel of a book in hand, and am sure some of you do too. Working out logistics on printing and distribution are a whole new thing for me, but print books are around the corner.

So to start off, I want to look at the ‘Water Chemistry’ portion of my book, which is essentially half of Brewing Fundamental 1.

When it comes to water chemistry, you won’t ever hear me say that I am the expert on the subject. I do of course have my own experiences and opinions on it though. In the book I specifically mention a ratio of 2:2:1 magnesium:calcium:bicarbonate if building your own water. This is a simple ratio, and I find it to be expressive of well roasted and well produced coffees. Does that mean that other ratios of minerals cannot work? Certainly not! The fact is that I have yet to find any consistent correlation between the necessity of wildly different water chemistry based on a coffee’s roast, or its basic nature. So to give any sort of definitive suggestion on water components to always use would be irresponsible of me.

In getting the book together, I did look to someone with a much deeper knowledge of water than myself; Maxwell Colonna Dashwood. He gave me a lovely quote to use, which we unfortunately were not able to insert in its entirety. Here is what he said:

“Water - the cradle of life, and more importantly the key to a great cup of coffee. 

A cup of coffee is made of water and dissolved coffee solids. sounds simple. 

However, water is an incredibly complex topic, So complex that scientists still don’t fully understand it. You will have tasted the impact of this complexity in coffee many times, often you taste it through a confusing and frustrating coffee making experience. 

You ask yourself “ Why does this coffee taste so different?” You make the same coffee with the same equipment, brew recipe and technique and the result is almost un recognisable. 

The likely culprit is the water

Coffee is so challenging as there are so many variables that affect the cup profile and it can be hard to disseminate them. Waters full impact however often seemed to go un recognised with other variables being blamed for the cup quality differences. However as brewing scrutiny and knowledge has developed waters impact has become a pillar of cup quality. 

There are several concepts and measurements to consider in water. Essentially we are interested in both the waters extraction of the coffee and its management of those extracted compounds. The water composition that you start with - your brewing water - will both impact what you extract from the coffee and perhaps more surprisingly it will affect how those extracted favours are presented in the cup. 

It is also important to note that the minerals themselves have a varying intensity of character and flavour also.  

The minerals to watch 

It is widely acknowledged that you require a few key minerals in the water to aid extraction and cup quality. Research suggests that Calcium and Magnesium have a high binding energy, meaning they will alter the coffee compounds extracted. Water needs a balance of positively and negatively charged ions and both of these are positively charged and called cat ions, so the water will need other compounds for balance such as sulphate which is called an an ion. 

Calcium is the more common influential cation in most waters occurring naturally around the world. 

Watch the acidity disappear

Without doubt though, the biggest impact on the coffee flavour profile is the buffering capability of the water which is linked to the bicarbonate content of the water. The buffer seeks to stabilise the PH of the liquid. Coffee is mildly acidic and the buffer cancels out the acidic compounds by turning them into the non acidic version of themselves called a conjugate partner. 

The thing about the buffer is it can change the cup profile dramatically after extraction. A really easy way to see this is to brew a cup of coffee and then drop a tiny pinch of baking soda 

(sodium bicarbonate) and watch all of the the acidity in the flavour profile disappear.

Measuring the water 

Traditionally the TDS of a given brew water would be measured and used as the metric. This metric is roughly indicative of the water’s hardness, but ultimately it doesn't tell you which minerals are making up that hardness. titration drop test kits are the easiest way to understand the different components in the water

The Right Water 

The kicker is there is no “right” water. There is a a rough ballpark that the speciality coffee industry can agree on as being desirable, however things get very complex as essentially coffees are roasted to taste best with the water being used in the quality control feedback loop at that particular roastery. 

 I personally have different preferences based on the coffee and its flavour profile. Very soft waters can benefit a low acid high floral coffee, as all the aromatics can shine. However with a fruit forward coffee this kind of water will likely present as sour. 

Then there is brewing methods. The big difference is between espresso and filter coffee. We discuss water composition typically in parts per million. However we use much more ofthis water to make filter than espresso. This means that the espresso actually has far less of those minerals relative to the coffee compounds. 

With this in mind it appears that espresso can benefit a higher concentration of minerals than filter coffee. The challenge here though is the very minerals that can help balance the cup can also cause scale in the espresso machine. 

In Summary, we definitely have more to learn about water and the answers will likely never be simple as stare contributes to the most varying and subjective element of coffee - the flavour profile. 

Water is now, and rightly so, recognised as playing a vital and unavoidable role in coffee quality and flavour.”

I feel that I said a few similar things when initially writing my book, but he does seem to be getting closer to correlations between a coffee’s nature and the water that works best with it. I really appreciate the time he took to write this for me!

FYI, he is in the midst of launching his PEAK Water jug, so be sure to check it out. It sounds like pre-orders are available now if you missed out on his Kickstarter campaign.

Of course I don’t want to forget my friends at Third Wave Water for water knowledge. They generously helped me with a few things, least of which was the filter magnifications and photography! Their product is a great solution for home or small scale brewing use as well. The spec of their product is as follows:

Magnesium ~90 TDS or mg/L

Calcium ~50 TDS or mg/L

Sodium ~10 TDS or mg/L

Alkalinity of 0 or ~0 KH

PH of ~6.6 This can be difficult to measure b/c most PH meters need a bicarbonate to accurately measure, so if a PH meter is giving a crazy reading is giving a useless measurement)

I have found it to make very tasty brews as well, though it is of course a bit different from individual mineral manipulation.

Another thing that I find timely is that James Hoffman just released his newest video series called “Weird Science”.

This video is interesting to me, as it begins to discuss the nature of water minerals and their interaction with coffee. The video is quite brief unfortunately, but I think he does what he does best: Bring questions to the viewer’s mind.

From here there are a lot of questions to ask indeed. Does a different mineral composition influence how much we may want to extract? Does the roast style have an influence that can be overcome? Is the coffee’s age less of an issue if we can hard bloom to remove excess gas?

I can always speculate, but most of these questions need thorough testing to find the real answers. And of course, as always, every coffee will behave differently.

In conclusion of water chemistry, this is a hot topic, but a very complex and difficult one to provide answers for definitively. It is also one of the least controllable elements of a real-world coffee service environment, especially ones with a high volume of drink sales. For that reason I do suggest that cafes find a good and consistent source, with regular filtration maintenance, and work on your other brewing parameters to create the best expression of your coffee.

Hope this creates more clarity on water chemistry! I will dig into more soon. And if you haven’t yet, check out the book!

Posted on July 24, 2019 and filed under Blog.