Conical Vs Flat Burrs – Which one’s best?

We’ve recently updated our ‘Buyers’ Guide to Coffee Grinders’. If you’re thinking about buying a new coffee grinder then we strongly recommend reading this article first.
conical vs flat burrs - which one's best?
There’s one part of the guide which we wish we could have wrote more on, but as we wanted to keep the guide fairly concise we decided not to (we didn’t want to bore you with too many details!). So I thought I would take this opportunity to write a blog post to expand on the issue.

The issue in question is about the shape of the burrs the coffee grinder is fitted with. Which one is best: conical or flat burrs? In the guide we wrote the following:

“The discs on burr grinders come in two different designs: flat burr and conical burr. It’s often said that the two different shapes influence the flavour profile in the resulting coffee. Flat burrs are thought to highlight the sweeter notes, such as chocolate, vanilla and caramel; whereas conical burrs are thought to highlight the brighter floral and fruity notes. However, this has not been substantiated; there’s no evidence (well at least not publically available) to support it, and so we recommend it shouldn’t influence your choice of grinder too strongly.”

I’ll be the first to admit that we’ve sat on the fence with this issue. But the truth is we’re not sure whether one design is necessarily better than the other. This is because it’s impossible for us to conduct a side by side test. There isn’t a grinder on the market (as far as I’m aware), that comes with the option of either flat or conical burrs, whilst the rest of the spec remains the same, and it would be unfair to compare grinders with different specs as any variations in flavour couldn’t be put down to the burrs alone. The only way to do a truly comparable test would be to build the two grinders ourselves – which understandably we’re not going to do.

The fact that there’s not a grinder on the market with the option of choosing the burr shape, suggests to me that the issue is far more complicated then just down to flavour. After all, if you could choose the flavour profile your coffee grinder highlighted, or even have the ability to swap the burrs and alter the profile depending on the coffee, or brewing method you’re using, then I would think this would be a strong selling point. I’m sure plenty of people would be willing to part some cash to buy such a grinder. I don’t think you can put this absence of such a grinder down to grinder manufacturers simply ‘missing a trick’, there must be more to burr shape than flavour profile.

I’m certain that the various grinder manufacturers, such as Mazzer, Macap and Mahlkonig, have invested a substantial amount of time and money into experimenting with different burrs shapes and know what affect, if any, the shape of the burrs has on the flavour profile of the coffee. But they’ve keep the results of their research private as this information gives them a competitive edge.

What can we learn from the grinder manufactures then? Well from a logical perspective, if they found that one burr shape was better than the other, they would surely deem it to be more valuable. If conical burrs were better than flat burrs, then grinders fitted with conical burrs would be more expensive, and vice versa. However, if we look at all the different grinders currently on the market, there appears to be no correlation in retail price and burr shape. Both types of burr shape are fitted in relatively cheap grinders as well as top of the range grinders. Again this would suggest that’s there’s more to burr shape than flavour profile.

relationship between burr type and retail price

Click image to enlarge

Personally, I don’t think burr shape can be considered in isolation. There are more factors to consider, such as motor power and speed as well as the size of the burrs. I’m not an engineer but I believe all these factors are inter-related; you can’t change one without the others. I’m not the only one to think this way either – check out this interesting blog post by Londinium Espresso.

So now you know why we’ve chosen to sit on the fence over this issue. Feel free to put us in our place if you think we’re wrong.