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Flat vs Conical
About the differences between conical and flat burr grinders for coffee.
Published December 20, 2021
Daniel Hedlund
The Coffee Lab
@ KOC, Kenya
Daniel Hedlund
Expert@The Coffee Lab
If you want to start brewing your own coffee at home, then you’re going to need a coffee grinder to produce fresh coffee grounds from your beans. While you can buy pre-ground coffee that can be convenient and, in some cases, ideal to get started with while you are learning the ropes, it’s worth bearing in mind that pre-ground coffee does not stay fresh for very long, and even if you store it in an airtight container, the final taste of your coffee is going to be affected as the coffee grounds lose their freshness over time. Since whole beans stay fresher for much longer compared to coffee grounds, grinding them each time you want to brew coffee is a much more cost-effective method that will lead to better-tasting coffee overall.
When it comes to grinding your own coffee at home, it’s important to choose the right grinder for your needs. Blade grinders are easy to get hold of and cheap to buy, but the big problem with these is that they don’t offer a consistent grind, which leads to some parts of your coffee grounds being larger than others, ultimately resulting in some of the coffee being under-extracted while other parts of the coffee are over-extracted. Because of this, investing more in a burr grinder will be the best option for anybody who wants to get great coffee at home. Burr grinders offer a much more consistent grind, providing you with the perfect type of coffee grounds whether you want to make espresso, filter coffee, or French Press coffee. Along with this, this type will also typically offer more control over the grind and allow you to adjust it in small increments.
Which Type of Burr Grinder to Use
While it’s a generally accepted fact in the coffee industry that burr grinders are better compared to a blade grinder, the next decision to make is whether you should go for conical vs flat burr. A typical home burr grinder will usually have conical burrs, as flat burr grinders tend to be much more expensive, and are harder to come by as home appliances, unless you are willing to spend around a thousand dollars for one, although that is changing. However, there is no need to worry since both flat and conical burr grinder types will produce the excellent, consistent grinds that you want to make the perfect coffee for you. So, what is there to know when it comes to conical vs flat burr grinder options?
Conical Burrs
If you look inside most burr grinders, whether it’s a small hand grinder, a large electric grinder or even a higher-end batch coffee grinder that’s a part of a commercial coffee machine, chances are that you will find conical burrs, since these are the industry standard right now. This type of burr has an outer burr that is serrated, with a center burr that has a cone-shape, which gives these burrs their name. The center burr will spin when in use, while the sharp edges pull the coffee beans into the grinding area where they will be broken down into smaller grinds.
Due to the shape of the burrs, this allows for uniform grinding with a high level of control over the grind size. A conical burr grinder is shaped very efficiently, allowing for lower RPM grinding which, in turn, produces less heat that could impact the quality of the coffee beans throughout the grinding process. Overall, conical burrs are easy to maintain, and cheap to manufacture meaning that they are easier to obtain compared to other types.
However, what has caused a debate around conical burrs is the fact that they produce a bimodal coffee ground distribution. This means that if you were to grind coffee beans with a conical burr grinder and then place them under a microscope, there would be distinctly small and large particle sizes. This will happen on all grind settings with this burr type. However, the two sets of particle sizes are what we have become used to, and they have played a huge role in developing espresso and how we make and drink it over the past one hundred years. The smaller set of grounds, known as micro-grounds, will restrict the flow of water in the espresso basket, allowing the larger grounds a little more time to extract, resulting in a heavy and often silky body. However, by the time the large grounds have gone through a more balanced extraction process, the smaller ones will have over-extracted, with adds bitterness to the cup.
Conical burrs work best for making a stereotypical shot of espresso, which is intense, slightly bitter, and with a thick body. However, since the conical burrs do not provide a truly uniform, or unimodal distribution of the coffee grounds, the coffee is limited to this body and flavor realm.
Flat burrs were first seen in the spotlight at the World Barista Championships in 2013. At this time, some of the most talented professionals in the world of coffee were able to experience espresso like never before, and since then, the debate between flat vs conical burr grinder for espresso.
Pros and Cons
There are various different pros and cons of the conical burrs, including:
Pros:
- High control level
- Low noise
- Low heat
- Low energy
- Low cost
- Produces coffee with rich flavor and a heavy body
Cons:
- Limited possibility realm
- Bimodal distribution
Flat Burr Grinders
While flat burrs for espresso grinders are not a new thing, the realization of their potential is. Flat burrs are differently shaped in terms of flat burr vs conical burr grinder options. They come with two burrs shaped like donuts with razor-sharp edges, that face one another. When the whole beans are fed into the grinder, the inner teeth grab them and force them through to the outer part of the burrs, where there are more precise, frequent teeth.
Since the burrs in this type of grinder face each other parallel to the counter, there is a larger number of grounds that are retained between the sharp teeth. Conical burrs, on the other hand, don’t tend to have this issue since rather than being shot out from the sides, the grounds fall from the bottom of the burrs. Along with this, coffee beans tend to spend more time being ground with flat burrs compared to conical burrs, which leads to more friction and in turn, more heat generated. These grinders also require a stronger motor for spinning the flat burrs, producing a louder and more high-pitched noise in comparison.
While the additional heat, noise and energy used to grind coffee beans using a flat burr grinder might lead some to think that they are inferior, it’s difficult to be set on an opinion once you have tasted the difference in the coffee. This is due to the fact that flat burrs achieve unimodal distribution when grinding the coffee. When looking at the grounds using a microscope, there is only one grind size. This level of uniformity and precision means that a skilled barista can pull various different types of espresso from the classic, gritty and thick shot to a brighter, sweeter, and longer shot.
Flat Burrs Impact on Coffee Extraction
In general, most espresso drinkers prefer to drink a shot of espresso that has extracted between eighteen and twenty-two percent of the coffee beans into the brewed coffee. Under eighteen percent will leave you with coffee that is under-extracted, weak, and sour, while over twenty-two percent and you’re going to be left with coffee that is dull, bitter, and has a muddy flavor due to over-extraction. With flat burrs, there are no fine grinds from the bimodal distribution that will extract too quickly, allowing you to focus on just one size and extraction rate rather than worrying about balancing the sweetness of the larger particles with the bitterness of the finer ones.
The unimodal distribution that you can achieve with a flat burr grinder means that there is no bitterness from micro-grounds as would be the case with bimodal grounds from a conical burr grinder. Instead, it produces a very sweet, ripe flavor and allows you to pull shots that are two times as large compared to a classic espresso without ruining the taste. Without the presence of two different grinds, it’s possible to manipulate the flavor of the coffee in a way that until now was not possible. This has resulted in a completely new world of espresso body and flavor, providing an opportunity for baristas to become more creative in their work.
Pros and Cons
Flat burrs also have a range of pros and cons to be aware of. These are:
Pros:
- Higher percentage of extraction is possible
- Unimodal distribution
- Greater variability and creativity when making espresso
Cons:
- More energy
- More noise
- More heat
Conical or flat burr grinder choices might not be much of an issue for you if you just want to make a good cup of black coffee. And for the most part, a conical burr grinder will be the ideal choice for anybody who wants to make the ideal shot of espresso or espresso-based drinks at home.
About the author
Daniel Hedlund
Working with the Era of We initiative and loves knowledge sharing and a really good cup of coffee.
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