Research & writing done by Chloë Sizer.
When we think about what constitutes a delicious cup of coffee, there are a few variables that vastly change our taste experience. Coffee origin, grind size and different types of equipment all have an impact on the final cup, but nothing is more important than the water we brew with.
The coffee we drink is predominantly water. For filter coffee, water constitutes about 98.5% of the cup and for espresso around 90%, therefore we should not underestimate the importance of water’s role in the extraction process. For simplicity's sake, the quality and usability of water for coffee is determined by three things: general hardness, carbonate hardness and undesirable compounds.
The composition of water is made up of a myriad of elements, the most important for coffee extraction being magnesium, calcium and bicarbonate. Each individual component affects what, and how many, compounds are extracted from coffee which heavily influence the overall flavour and cup quality. General hardness is essentially the amount of magnesium and calcium present in the water, and both can have a dramatic effect on water quality and composition.
When we look at the hardness of water, we are considering the balance of minerals required for optimum taste experience. Generally speaking, softer water will extract coffee differently than harder water, resulting in a delicate brew with prominent, yet potentially unpleasant, acidity. Harder water with lots of bicarbonate will make for a duller coffee with a muted, muddy flavour profile.
Where general hardness overshadows the effects of calcium and magnesium in water, carbonate hardness looks at the relationship the minerals have with bicarbonates.
They are used as ‘buffers’ to soften the acidity in coffee, but it is important to have the right balance. Too much bicarbonate and you run the risk of nullifying the pleasant acidity naturally present in coffee resulting in a chalky, lacklustre brew. Too little can cause your coffee to taste unpleasantly sour or vinegary - depending on the coffee!
The water we choose must also be clean, odourless and free of undesirable compounds which are present in unfiltered water. Where some minerals are necessary for coffee extraction, not all are going to make your coffee taste pleasant. Tap water can be the biggest offender in this category as it often contains elements that can compromise the quality of your brew.
Have you ever drank water from the tap and experienced that metallic taste? This is usually due to minerals that are either naturally present in bedrock or the result of corroding metal pipes. This is not to put all tap water in the same box. Water quality is much dependent on the source yet filtered water is still considered best for quality, taste and even equipment maintenance.
All this to say, there isn’t a specific standardised recipe for coffee water. The SCA (Specialty Coffee Association) provides an optimal scale range of 50-175 ppm (parts per million) general hardness with a respective 40-70 ppm carbonate hardness. Many professional and home baristas are now ‘building water’ from scratch to experiment and push the boundaries of coffee brewing as we know it.
You could argue that preference plays a big part in choosing the water that suits your coffee best and this is what makes water chemistry so exciting. I decided to conduct an experiment of my own to see if I could taste the difference different types of water have on brewed coffee and to see if there was any variation in people's preferences.
To do this, I initiated a blind cupping with three different types of water and measured the total minerality content with a TDS (total dissolved solids) metre. This is a super handy tool if you are ever curious about the water you want to brew as it can give a good indication of its general properties and quality.
The first water I chose was our cafe water which had a reading of 96ppm sitting comfortably in the middle of the recommended SCA range. The second was unfiltered Calgary tap water which had a reading of 187ppm outside of the range and is a typical example of ‘hard’ water. My third and final water of choice was the bottled, filtered water. I chose the brand Aquafina as I wanted to use a water that was on the softer end of the scale, coming in with a reading of 2.5ppm.
For the cupping, I wanted to compare two very different types of coffee to see if the different types of water would affect the taste, quality and preference depending on its variety and processing. The first coffee I chose is one of our exceptional releases, a red honey gesha from Monteverde located in Colombia. This coffee is well respected across the board for its pleasant acidity and balance of delicate flavours. I compared this coffee with a selection from our warmer coffees, the Ramiro Martinez, a washed Guatemalan known for its more traditional, smooth, easy-drinking profile.
The cupping itself was controlled by using the same temperature water (200℉) boiled the same time with each cup containing the exact same coffee weight, grind and water volume. Each coffee brewed for a total time of 4 minutes and was tasted both hot and cold to see if this had any affect on the flavour profile. I used the scale of low to high to determine each brew's acidity, bitterness and sweetness and asked a team of six volunteers (including myself) to evaluate.
Below is a condensed version of my findings:
For both the Monteverde and Ramiro coffees, I preferred the cafe water for overall balance of flavour.
The water from the cafe helped to highlight the exceptional acidity this coffee had to offer. It was bright and juicy and the more balanced of the three. The tap water had nothing to offer this coffee at all which is probably due to its hardness and high bicarbonate nullifying the acids needed to bring the coffee to life. This isn’t to say it tasted overwhelmingly unbalanced, but it was flat and uninspiring compared to the cafe and bottled water which both highlighted the coffee’s unique qualities. It is interesting to note the popularity of Aquafina. Personally, I found this brew to be pleasant, but it was highly acidic verging on the point of sourness which is probably due to the lack of buffer and its overall softness.
The overall consensus was that the cafe water created a better balanced brew suited to this type of coffee. The roasting profile for the Ramiro differs greatly from that of the Monteverde and as such, a bright acidity is not to be expected. Yet it is interesting to see the Aquafina highlight this quite intensely. The fact that two people chose this as their favourite shows how important a role personal preference can make when choosing a water to brew with.
Overall this cupping helped to highlight how different types of water affect coffee extraction, not just by numbers and readings but also taste and preference. The type of water we use is just as important as the coffee we choose. Think of it as akin to choosing flour to bake a cake: the higher the quality and balance of ingredients, the tastier the outcome. Yet water is not a one size fits all concept. Like choosing coffee beans, personal preference is most certainly at play when it comes to choosing your water profile.
If you want to experiment with water, it isn’t as inaccessible as you might first think. Building water from scratch is precise but still doable, but you would need a lot of different components like distilled water, minerals, and a scale precise enough to measure tiny quantities. Though it is a little bit of an investment, there is more room to trial different recipes to see which suits your coffee best. To make it more accessible, you can also purchase pre-packaged minerals such as Third Wave Water that you simply mix with distilled water. Though there’s less room for experimentation, it is an easy, quick way to have readily available water for brewing.
Remember, good things come with time and practice - the same goes for brewing coffee…with the addition of a lot of tasting!