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By: James Fairweather 13 July 2020
As the only ‘coffee guy’ in my group of extended friends, I tend to get bombarded with a whole host of coffee based questions. Which, I am more than happy to entertain… honest. In fact, one of the best things about my job is being able to share the knowledge I have to spread the word about the incredible work our amazing producing partners are doing all over the world.
The most common question I tend to get thrown my way though is… “What is the most important thing I need to make a bangin’ brew?” And although there are plenty of ‘things’ and a lot of different variables associated with brewing a mighty fine cup of coffee, I totally get it. Coffee paraphernalia tends to be expensive and unless you’re a bit of a nerd like me, you’re probably after a tasty cup of the good stuff in as little time, for as little effort and expense as possible. And for that reason the answer I always give is… “It’s all about a decent grinder!” Hand powered or electric. Doesn’t really matter. But it needs to ideally have burrs, blades are a no-no. (I’ll explain more about this later)
Ok, so “why a grinder?” I hear you ask. Well, if you have never compared pre-ground coffee against freshly ground to brew then you are in for a treat – you really will not believe the impact this has on the quality of your brewing experience and for that reason, grinding fresh should be top of your list when trying to improve your home brewing game. There are many variables that affect how your coffee tastes: time, temperature, brew device… But the most powerful tool in brewing better coffee, assuming you have top beans and decent equipment, is grind size. And this is down to the direct impact this has on extraction.
Without getting too technical, extraction refers to the process of transferring the flavour/aroma compounds from your coffee beans into your hot water. Water dissolves these compounds and these dissolved flavours make up virtually all you taste when you sip back on your freshly brewed cup of coffee.
Now, seeing as only around 30% of a whole coffee bean is soluble in water, it becomes necessary to break the bean down, unlocking these flavour compounds and making them more accessible. This is achieved by grinding the beans, effectively opening them up to extraction by exposing more of the bean’s surface area to water. So quite simply, the FINER you grind your coffee, the MORE FLAVOUR that is EXTRACTED into your water over the same period of time.
So, why don’t we just grind as fine as possible and extract all of the flavour the beans have to offer? Unfortunately, not all flavour and aroma compounds are the same and although some add desirable sweetness and fruity notes to your brew, others lend bitterness and astringency, which can lead to an unpalatable cup. And nobody wants a bitter beverage! To make things even more frustrating, these flavour compounds, both positive and negative, extract at different rates. Therefore, we need to control the degree of extraction taking place bu dictating the contact time between the coffee and water flowing through it. And the best way to do this is by grinding your coffee to the correct particle size for the brew method you are using.
Ok, so hopefully that makes a little bit of sense. Unfortunately this isn’t a one-size-fits-all approach though. There are a few more factors that affect grind size and these need to be considered before we end up achieving that perfect, well-balanced brew time after time:
1. BREW METHOD/TIME
Both are inextricably linked when it comes to grind size. Brew time is dependent on the method you choose due to the different amount of contact time water ought to have with the coffee grinds in each method. For example:
FRENCH PRESS is a form of immersion brewing, i.e. the grounds are steeped in water for a long brew time, usually around four minutes. A coarser grind counter-acts the ‘risk’ of over-brewing the coffee using this method by slowing down the extraction.
POUR OVER uses a filter and the brew time is dependent on how long it takes for the water to trickle through the grounds. So, how fine or coarse the grinds are will directly impact the time it takes for water to drip through. Think of a glass of sand versus a glass of pebbles: pouring the same amount of water through each, you’ll see that water takes longer to pass through the finer particles of sand. As a result, brewers which use filters are better suited to medium-fine grinds.
ESPRESSO has a very short brew time, typically just 20–30 seconds, and uses pressure to force water through even the most densely packed coffee. This makes it better suited to a finer grind size to present more of a barrier for the water passing through ensuring enough flavour is extracted in the short time the coffee brews for.
(Click on the following icons to find out more info on the associated grind size for each brew method in our guides.)
2. ROAST LEVEL
Different roast levels also have an impact on how quickly flavour can be extracted from coffee grinds. For example, expect extraction to be faster in dark roasts because the beans are more soluble. If you are buying specialty coffee this shouldn’t really be an issue, seeing as most specialty roasters opt for a light to medium roasting style. However, it is worth noting that it may be beneficial to grind slightly coarser for darker roasts, and slightly finer for lighter roasts.
As with all fresh perishable produce, the sooner coffee is consumed (after an initial resting period), the better it tastes. And the better it behaves when brewing. We advise to buy little and often so your coffee is as fresh as possible every time you brew. However, in times when you find yourself brewing coffee that may have been in the cupboard for a little longer than expected, you may want to tweak your brew recipe. This is because coffee’s flavours fades over time. In this case, many home brewers tend to grind finer; others prefer to up the coffee dosage and grind coarser to compensate. The first option will increase extraction; the second, intensity.
Ok, so earlier on I mentioned that it is all about burrs when it comes to purchasing a grinder. The reason for this being better grind uniformity and consistency. Regardless of what grinder you choose though, it is worth pointing out that uniformity in grinding will always be an issue to a varying extent. After all, we need to remember that coffee beans are a natural agricultural product, which will never break down into nice evenly sized pieces. Ground coffee contains a mixture of larger and smaller grind particles and these extract at different rates due to the difference in surface area. The amount of these “boulders” (larger particles) and “fines” (smaller particles) and their difference in size is determined by the quality of grinder you use.
The most inconsistent of which being a blade grinder… in fact, can you even call it a grinder?! Considering it’s mechanically similar to a food processor and very little grinding actually takes place. Instead, the blade chops and smashes the beans into pieces. And extremely uneven pieces at that. Increasing the likelihood of under-extracted boulders and over-extracted fines and leaving you with a brew with a muddled flavour and a recipe you’d struggle to recreate.
Step forward Mr Consistency… aka the burr grinder! There’s no comparison really. These are made up of two revolving abrasive surfaces (called burrs), in between which coffee is ground. The distance between the surfaces can be changed, which in turn changes the size of the grind. So you have more control over grind size and end up with a more uniform particle size. Much more so than a blade grinder! You also don’t get any issues with heat transfer from grinder to bean like you do with a blade grinder either, which can lead to deterioration in quality and flavour. Which no one wants…obvs!
So, in a situation where we have brewed a delicious coffee and are aiming to replicate the grind size that leads to this taste sensation, it makes sense to choose a burr grinder which is undoubtedly more consistent at producing reliable, uniform particles than it’s blade counterpart.
Hopefully this has given you a little insight into the huge role that grinding plays in helping to achieve a consistent well-balanced, tasty cup. We want you to get the best out of our coffee and this involves having the best possible experience when brewing it. It is important to reiterate that there isn’t really a universal approach in choosing the right grind size. However, as long as you have an understanding of the factors that can impact your brew and adjust your grind accordingly (using a quality burr grinder), you’ll be able to experiment and find the perfect grind suited to your personal brewing setup.
We may have only just scratched the surface when it comes to some of the mind-boggling science associated with grind size and it’s impact on coffee brewing but this should be enough information to set you off in the right direction on the path of great tasting coffee at home. Keep your eyes peeled and ears open on our social channels for more tips, guides and exciting developments in the coming months!
And if you are looking to add a grinder to your home brewing setup, we would recommend the following to get you started on the right path:
Rhino Hand Grinder (portable and sturdy – perfect for any setup be that home, the office, in a tent etc!)
Wilfa Svart Electric Grinder (if you want perfectly ground coffee at the push of a button)