To Burr or Not to Burr?

Any coffee nerd will tell you that in order to make a good cup, you need to have beans that are ground, not only to a particular size, but also a consistent size. If you’re making espresso, you’ll need a very fine grind, but for a drip coffee a medium grind is the way to go. But regardless, consistency is key. If you have grounds of different sizes, they will extract differently and affect your cup of joe.

Credit: GROSCHE

A fellow astronomer wrote an app that targets just this problem. How fine and how consistent are you grinding your coffee? I encourage you to check out his website for more coffee science.

I have two coffee grinders at home that I wanted to compare. A hand burr grinder, and an electric blade grinder. Burr grinders are designed to give you a more consistent grind size, since each bean only passes through the mechanism once; as opposed to blade grinders which just chop beans willy-nilly. America’s Test kitchen recommends pulsing blade grinders in 1-second intervals to get the best results. So does this actually work?

My two grinders. (left) a hand burr grinder, and (right) an electric blade grinder

For the burr grinder I’m using a $17 EZE Homegoods grinder, and for the blade grinder I’m using a $24 Krups grinder. In theory burr grinders should give a more consistent grind size than blade grinders. But are the 1-second pulses enough to make the results comparable? I went ahead and ground a few beans in each grinder and placed them on a paper sheet for imaging and added a quarter for size comparison.

Even without using the app you can already see that the blade grinder is producing smaller grounds than the burr grinder, even setting the later one to its finest setting. But this is also a question of consistency. I went ahead and loaded these images into the app to measure the sizes of each grain. And here’s the result:

As expected from looking at the images, the blade grinder is producing smaller grounds. But they’re also more consistent than the burr grinder! The sizes of the grounds from the blade grinder are from 0.2-2.0 cm2, whereas the burr grinder’s ground span 0.6-13.77cm2! That’s a lot of different sizes for something that’s supposed to be more consistent.

In conclusion. Even though burr grinders are supposed to be more consistent than blade grinders, using a blade grinder by pulsing it on 1-second intervals produced better results than a cheap burr grinder. Emphasis in cheap, my burr grinder is not a high quality one and I suspect that a decent quality burr grinder would be able to surpass the results from the blade grinder.

4 thoughts on “To Burr or Not to Burr?

    1. Thanks for pointing it out. I did mask out some of the ones near the center which were definitely clumping. But there might be more that I missed.

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      1. Ah ok nice, that would help. Another thing to keep in mind is that all grinders will have varying spreads vs grind size. It would be ideal to compare both with the same peak location, but I know that’s a lot more work. If you have a scanner, it can really help getting a more stable pixel scale too. Email me if you would like to spend a couple hours gathering more data, I’d be happy to help you. I also have codes to build much better PSDs with kernel density estimates and you can combine multiple CSV files from the app for better statistics. They’re IDL codes for now but I’ll eventually translate them directly in the grind size app. I’m happy to see another astrophysicist get into coffee geekery 😀

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