COFFEE SCIENCE - How Grinder Speed Affects Extraction & Taste 

An interesting possibility is if RPM can expand the versatility of a burr enough to eliminate the need for multiple grinders, e.g., What’s the difference between Multi-Purpose at 1400 RPM vs. High Uniformity at 200 RPM?

Really thankful for this video. I've been wanting for someone to make a video on this for a long while, really happy to see you making one! Now I hope others make videos on this topic, too, so we can get more opinions. :)

Another excellent video. Thanks, as always, my friend.

Thank you this video. A topic that I have not seen much on YT. I have been social isolation for health and covid reasons and so not need a new grinder to make that even worst ;-) Keep up the good work, always appreciated !

For the next test it would be nice to do 300/800/1400 rpm on both conical and flat burrs and compare them side by side !

Thank you for this info. I appreciate it and the content you share.

Great vid as always! Would be interested to see how this changes by roast level. Perhaps, even a comparison between a dark, medium, and light roasts by low, medium, and high rpm, but that’s starting to get into crazy ANOVA territory lol

thanks for ur honesty in thinking basically no significant difference between high, medium or low grind speeds. if i were to come to this conclusion on some reviewer channels i'd be belittled and condescended upon despite making espresso since before some of the reviewers were born. not to mention getting attacked for expressing an opinion despite nearly 40 years espresso experience, brewing, roasting, rebuilding machines.

I actually wondered the same question about grinder rpm. Not to long ago, me and my friend tested this idea out with our grinders. We found that like you, the lower rpm had just slightly more mojo to it. Better crispiness, sweetness, and even aroma, higher rpm made the coffee have a different smell from the lower rpm one.

I haven't read the BaristaHustle piece, but the temperature differences make sense; the burrs producing more heat and friction for the longer grind time required by a finer setting. Very impressive and timely video for the coffee community at large. I really look forward to the times when I have to rewind in order to really wrap my head around the technicality of it. (Don't worry, it all congealed by the end).

Hey man, as always a very cool and interesting vidéo ! I have a recommandation for a vidéo, if you find this interesting, I would very much like to see a vidéo on the C40 but with measurments, datas, différents types of filters, expresso, etc... A late breakedown of the commandante c40 we can say. I have one my self and would find that very interesting to see how someone with your experience could analyse (compare?) the C40 and explain how to get the most out of it ! Thanks for reading ! Love your vids anyway, Peace Nil

Without reading the article on grind speed and output temperature, I would expect your result for several reasons: 1. Lower speeds get the grounds through the motor more quickly, meaning less heat transfer from the motor or burrs themselves (lower contact time) and less heat from the energy released by the breakdown of the beans (because fewer such shatterings/crushings are likely to occur as each bean passes through the burrs in less time). 2. Higher RPM leads to more fines, which have to have been broken more times and/or more energetically. If you performed this test after adjusting the grind settings to have identical brew time, then this might not have been as substantial a factor, but the video just says "mid-grind" and you've also said that the profiles of the resulting coffee followed the same "common wisdom" of the clarity/sweetness outcomes as with finer or coarser grind size. 3. Higher RPM means more energy in the moving burr because it's moving faster, thus collisions involving it will have more energetic debris. In this case, that debris is coffee in the process of being ground and it has nowhere to go but further into the maelstrom, and so the grounds will have endured several such collisions and carry the energy (and at 7x speed that's 49x as much energy) of those collisions with them in the form of higher exit velocity (which you'd already remarked upon) and temperature. Some fraction of that excess exit velocity would also translate into heat, but some of that heat would be lost to the air if those grounds bounced and it's unlikely to compare to the energy gained from the many collisions the coffee experienced between the burrs.

Dont have one yet but Im waiting for a P64 in the same configuration as yours. Excited to try out some similar experiments.

Once agin a great video that will help me get a running start on a new grinder that is headded my way soon.

Super interesting. Would love to see similar experiments with a hand grinder. Obviously the range of speeds you can get with a hand grinder would be much smaller but I'd be curious if there's much of a difference. I imagine consistency makes a difference there as well (I.e. do you speed up or slow down throughout the grind). Would be difficult to measure your speeds though.

I upgraded my grinder from 1-10 to 11. Next level.

Very interesting experiment. Thanks for doing it. Here's a question: what happens to your experiment if you pull espresso with a paper filter at the bottom?

Great video, I think grinder speed is interesting but adding the extra parameter to an espresso workflow just doesn't seem worth it. Ideally coffee grinder companies would offer RPM settings that either promote clarity, body, or a middle ground like the SSP high uniformity and multipurpose. But logistially I think I would prefer getting SSP high uniformity over a slower grind just because I'm impatient and feel like it would be a "better" upgrade for that type of brew.

Thank you for this interesting video. What dial setting corresponds to 800 rpm? 5?

Amazing breakdown. I've heard several people talk about the preference of a hand grinder when it comes to conical burrs stating the lower RPM reduces the amount of fines. That would seem to hold up with your findings.

Try making a video on all the different burrs. I wonder if they make a ceramic burr. I have a ceramic 54mm and steel for my baratza vario-w. The ceramic has completely different teeth patterns. Someone said “Less teeth maybe more crushing then cutting” so I switched my steel burr back to ceramic to get a more balanced cup vs bright/high clarity cup from the steel burrs. Currently using a ECM classika single boiler with PID and flow control and it’s been a lot of fun! Would love to try a p64 but for now the vario-w with flat 54 will have to do!

Did you get a chance to play with the RPMs with the Weber Key when you had it? Strangely some say the shot timing gets SLOWER (longer shots) with LOWER RPM which sounds like it has more fines at lower RPM (but by taste, it doesn't, since it still has higher clarity / cleaner results at lower RPM and maybe more body at higher RPM).

Thank you for experimenting and putting up some numbers. I wonder if your results would differ with a conical grinder. I chase body in my espresso, so I'm now wondering about how fast I can crank my hand grinder without hurting myself lol. Might be time for a drill :)

No many baristas do experiment on the rpm speed of the motor of the coffee grinder, this is interesting find.

Upcoming article from Jonathan Gagné's blog suggests that the trend "more speed gives more fines" depends on burr geometry: some burrs will behave in the contrary way while some others will not show significant difference.

It would be cool to have some collabs on these video's. Have 2 creators in the coffee world discuss these tests would be sick

Liked the video. I won’t lie, I’ve repeatedly seen written that “slower RPM means more heat” and I just don’t get it. Inevitably, the same kit grinding slower will take longer to complete grinding, so the energy to grind the beans will generated over a longer period of time, reducing the temperature increase. Your observation of fast speeds being hot and grinding slowly implies there’s a lot of stuff going on in there generating heat that isn’t actually contributing to the coffee getting ground. Whether this is the grinder itself generating excess heat or potentially the coffee itself pinballing around the chamber and not getting into the burrs.

love the nerdy data....

Spro I'm wondering what the rpm would be using a conical burr grinder to achieve the equivalent result to your 800 rpm for the most balanced espresso using flat burrs?

great video. Who'd a thunk an adjustable speed grinder is even a thing? Interesting results though. Seems you could extrapolate your findings to hand grinders which will likely in the 200 rpm range (or less), suggesting that hand grinders are a good thing for espresso and maybe a good thing for pour over if you like a bright cup.

Lagom recommends speed number 3 on the p100 for everything from espresso to filter. I think that's around 580 RPM? Not sure what their recommendation speeds are on the p64. Interesting tests! Thanks for the all the data.

What is the pour over dripper stand at 1:08 ?

I am wondering about RDT and clumping. I use a ROK Grinder and find it does benefit from RDT to minimize retention. BUT, the process does seem to increase clumping compared to no RDT. Even using one spiritual will have a small, but noticeable increase in clumps compared to no spritz. Has this been tested?

Hi, which scale model are you using?

I'm just a casual coffee consumer. Since grinder quality is rated primarily on coffee granularity and consistency the output on varying speed should likewise be priority. What would be interesting is measuring the heat generated on the burr and grounds and if the variation on heat if any has any effect on taste.

There is this thing called voltage regulator that can give you the RPM control for any of your grinder, it's inexpensive as well, flat burr grinder seems to get better results at 800 rpm and why not try it?

Great video! I think it would be interesting doing this but reversed: try to get the same-ish cup with different RPM but adjusting the grind and/or quantity of coffe, to see how that affects other factors, like retention and grinding time, among other thing that I might be missing out. It could also be useful in order to get a general idea of the coffee profile that a grinder has based on its specs.

A year later how are you feeling about these results? Anything you’d add? I’m getting a df83v which has a variable speed control and I’m trying to learn about how I can use the different speeds. I brew medium roast espresso generally drank as americanos. Thoughts?

What kind of SSP do you use?

Maybe this is just me but I would use variable speed to recreate the taste of hand griding. Hand grinding is about 120rpm with is close enough to 200.

So, is it possible to plug one’s grinder into a “Variac” type device?

Any differences you noticed with the roast level--light versus medium versus dark--related to RPM speed? Do certain roasts work better with certain RPM?

I have a Eureko Mignon (flat, 1400rpm) and Weber Key (conical, 30-150rpm). My 1:2 espresso has muted bitterness but more body from the Eureka, while the Key always give sweeter but less body shots

Timemore basic pro scale?

how was the temperarture of the coffee after grinding?

LMFAO! Extreme social isolation. You sir are hilarious.

It shouldn’t be counter intuitive that higher rpm increases heat - kinetic energy is proportional to velocity squared where as time is just a linear proportion

For the espresso, at same grind size, how the rpm affect the brew time? Does the lower rpm will make the shot faster or slower?

thx king

Do you think the results will be similar if you grind quicker or slower on a hand grinder?

"...those coffee nerds looking to take the next step into extreme social isolation." I feel attacked.

using my hand grinder, I will have to try grinding faster... lol (seriously, I have been contemplating connecting a hand drill to see what difference it makes in the cup)

did u measure acidity with a Ph meter?

You had to grind finer for espresso at 1400 rpm compared to 200rpm? higher speed= more friction= more heat, adding heat to beans means you have to grind finer (see the microwave heated beans experiment before grinding).

Extreme social isolation - with a wry smile.

Dark horse coffee!!

Waiting on the Acaia orbit which should be shipping with RPM adjustments. I don't think it'll preform much different than the P64 though. This month, it's Bunzilla month.

Wait, are you saying you changed the grind size for the espresso to reach the same contact time and yield? This test doesn't seem useful without knowing how you had to adjust the grind size based on speed. Is it possible the difference in extraction and flavor just comes down to the fact the you adjusted the grind size?

Nice topic, now I want try to change the RPM of my EK43, anyone try ? Otherwise I need to looking for a voltage reducer

With about a 1% difference, any explanation you give means very little because you can't tell if the result is statistically significant