6 Bar vs 9 Bar: The Impact on Espresso 

MUST READ: First, I've been reached out to by a university that has done this same test and have arrived at the same data. This will be published soon(ish) Some supplemental information for those not wanting to look at the data! There was no statistically significant difference between shot times or extraction yields between 6 and 9 bar. For tasting, other than the odd Alaka, the results were random. Qararo- I chose 6 bar thrice and 9 bar twice, Rui chose 6 bar twice and 9 bar thrice. Leona Tabi- We both chose the same cups identically- three 6 bar shots and two 9 bar shots. Alaka- We both chose 9 bar for each one, but I suspect this is separate from pressure threshold. Please leave a like and comment if you enjoyed! Or, if new to the channel, a subscribe would be awesome! Cheers and looking forward to chatting below!

Prediction: eventually, Lance will determine the ideal espresso is pour over

Lance dropping… bars. Ok, I’ll see myself out.

The Burr Man? Nooo…the Bar Man. Thanks for raising the Bar, Lance. I know creating this content can be a lot of Pressure. When it comes to the coffee community, I nominate you as the Group Head. 😬

Lance asking the questions that have real value for both home and professional coffee consumers. Thank you. Honestly I'm very happy you make videos and I found them.

“Vomitable” great word of the day.

Lance as an engineer and research scientist it’s fantastic to see your use of the scientific process to brewing better espresso. You have tremendous resources relative to most home baristas, so I really look to your testing to shed some light on what all these factors do! What’s crazy is that many people, including people around me in my community, get tripped up by their own biases and critical thinking to discern what can be objectively relevant data. Thank you for acknowledging what is tested data and understanding the limitations of what has been proven vs what is speculation

Data-driven coffee content is what every coffee channel should do. Thank you Lance

Keep chasing the dopamine, Lance. Keep pushing against assumptions and pressing into the data. You're a big encouragement to us all!

This was exactly the testing I was hoping to find a few months ago. Thank you for all your hard work, Lance!

FTR, when I started trying to figure espresso out, I found Lance and James early on. I've found many others now. Some very helpful. But still, it's Lance and James the produce content that continues to excite me.

Thank you !! I have learned a lot from all your videos. I also believe that flow rate of the puck is the most importance.

For once, a video saying that it's OK no need to change anything, what a relief!

Vindication! Last few weeks I've basically stopped worrying about pressure as a variable. As long as I'm hitting my ratios and times the pressure naturally trends to around 7-9bar anyway, and the results have been great. This hobby is fun.

I am just here to say i love these kinds of videos, keep it up!

Lance consistently dropping knowledge and relieving head aches haha. I can stop worrying about pressure now and remove one more variable to stress over.

Well, since my Apex has a 15 bar pump and no OPV, most of my shots start about 11-12 bar and go down from there. But I've definitely had the grind a bit too coarse a few times and started closer to 8 and averaged about 6. Tasty coffee basically every time. I appreciate all the work you do here. Also that white decent with the hummingbird looks absolutely phenomenal. Can't wait for my hummingbird to come in.

never thought i would out a coffee youtuber on Hoffman's level, but in recent times i have found myself going to your channel over his.. many thanks for all the info and gems... and ofc music.

Remarkable work, Lance.

FANTASTIC! Been SUPER wondering the answer to this question!

Awesome shirt man, also: is there a review on the Kafatek coming? Loving the videos!

That's why I love direct levers - I don't really know what pressure I'm pulling, the effort I have to make depends entirely on grind size, puck preparation and resistance during the shot and not the other way around. Great video!

Really raising the bar with these videos

TBH, this is something I've been very curious about. Thanks for the data as always!

Good info thanks Lance!

love your approach to coffee, this feels like a breath of fresh air compared to most ppl in this hobby. Just had an happy accident today while trying a new coffee. Got it too course the first time, pulled 40 out of a 15g shot in 14 seconds or so, looked awful with the open basket. But bc broke college student I won't waste coffee, tried it and it was actually quiet nice.

Again, breaking the internet! Another great video, Lance!

Great video as always! I'm starting to believe that flow rate is one of the most important independent variables. It's also much easier to visualize dialling variables (grind size, puck volume, etc) in relation to their impact on flow rate.

I've been waiting for this one ❤

As you mentioned Lance, I believe it's more flow rate that determines the best cup in terms of flavour. While anecdotal, I have been pulling 15, 13, 11, and 9 bar espressos on my pressure modded breville infuser for the last year and have noticed that the taste is best when the flow is a finer stream. Since the flow increases as the puck deteriorates, adjusting the pressure to maintain a finer stream appears to produce a better tasting cup. I do 21.5g in to ~50g out, preinfusion at 3-4 bars for 6 seconds (including ramp up time) and anywhere from a 34-54 second pull depending on the colour and flow rate. If the liquid is quite light or clear, I end the pull by dialing down the pressure to 3 bars over 2 seconds.

Great video Lance, I want to add that I'm pretty sure keeping the duration of most of the videos under 20 minutes will eventually help to get more views. Finding interesting 12-16 min. videos in the feed is synonym of CLICK 😜

Soooo Awsome! You two just made history. I don't know much about light coffee, people always say they're more difficult to extract but overextraction ruins taste. Is it possible a 2:1 ratio on lighter roasts is too much? You didn't have to drop in a set of nconsistent coffee beans, but you did and that's even more awesome. Your sacrifice for science is Well appreciated ❤

Great vid! Thanks!!

Thanks for sharing another awesome experiment. Did I understand you to say flow could have more impact than pressure?

The little bit about natural coffees was very helpful. Do you have any video that compiles that kind of knowledge about how beans work ? I’m roasting at home and kinda lost my mind over that dynamic lol

Awesome day ahead with a new video

Gonna set up a 9-bar ExDos profile on the Decent for tasting tomorrow morning. I pretty much only drink naturals, so we'll see how it goes. Also just correcting my subscription status to the channel. Thought I was, because I see everything you put out, but take my plus 1. I also used to live in Bordeaux, nice to see they've got a decent coffee scene sprung up.

I'm really loving this recent run of experiments. If I undertand correctly, the biggest difference observed here (with the Alaka) was perhaps due to a greater change in flow rate during the shot, correlated with a change in pump pressure. Intuitively, it feels like changes in flow rate during the shot would affect the representation, e.g., of early vs. late extraction products in the cup, which would presumably affect the balance of the shot. As a "first order" extension on this, it's not clear to me how a flat flow profile (let's call this a "neutral" representation of extraction products) would compare with, say, a flow rate that increases or decreases as the shot progresses (presumably favouring either early or late extractin products). Do you have a sense of how simple changes in flow rate like this would affect the shot?

Thanks Lance

Very inspiring... Its teach me alot

Waiting for this finally!!!!!

Thanks again for the video. I think it will be very interesting in 30 years when we look back at this time in coffee history. How much more will we learn. I feel like everything we “learn something new”, we learn there is so much more we do t understand. Coffee is hard.

Interesting experiment. I love the results. I think is hilarious that we're looking for empirical evidence in something so subjective as taste. We want to validate being "correct" in our preference, so human.

I might have missed this, but what temperature were you doing for these shots? Seems like they were a constant variable throughout the experiment. Thank you for your contribution to the community. As someone who is new, these videos have been utterly informative to my experience.

Great discussion about pressure vs flow rate! Soooo interesting. Thanks Mr Lance! I guess for systems that build pressure via compressed Co2/No2, or just air, things might be quite different? Anyone any experience?

Another great video from Lance, thanks! As a Flair user, I wonder how this impacts the direct lever machines. It is easy to realize with the Flair that trying to keep up the pressure (by applying more and more force on the lever) throughout the extraction is a bad idea, and will result in very harsh tasting espresso and mess all around. So a declining pressure profile is definitely the way to go. But do you want to keep the force on the lever constant? Or the flow rate, after the coffee actually starts flowing? Or none of these and ease up even more (or less) towards the end? These are exciting and meaningful questions.

Strietmann in the back. Yeaaaaaa. Gimme that review please !

Why to choose between 6 and 9 bars? Just use both - go up to 9 very briefly, then go to 6, gives best results for me 😅

Great analysis. I would be interested to validate your results by comparing 6 va 9 bars for each coffee by comparing effects on different grind settings, rather than holding that as a constant. Because then the flow rate should be varying and it would be interesting to see how that compares from coffee to coffee with 6 vs 9 bars.

oh why thank you so much. American James Hoffman 😂 I needed this test.

Very instructive, but it’s kind of your signature. Flow to puck degradation having more of an impact on final result than pressure does make a lot of sense. Out of personal experience this may be the reason why my manual shots (Robot and Flair 58) may be a step above my e61 ones, even though I rarely pay too much attention to gauge and tend to rely on puck feedback. Also, thanks for getting me to discover a French roaster that was not on my radar. Will try them for my next order.

I settled on 8 BAR adjusted OPV in my Gaggia Classic. Good middle ground and works very well indeed. Much better than OEM stock (~12.5 BAR)

Fully agree. I created a "preinfuse - bloom - 6-to-4.5bar decline" shot profile for my girlfriend. Just accidentally used that profile on an Ethiopia bean ground for 9 bars. Best shot I've ever had for that coffee.

This makes me feel like I’m not missing out on anything by not adjusting my OPV to 6 bar, and that’s great because I really didn’t want to mess around with that!

Nice test 👌 Question: since the last coffee the shots were so fast were you hitting 9 bar? On my machine shots around 20/22s do not go past to 7bar

This is why I love my Micra with very little customizability. Just solid shots, one after the other.

Do any espresso machines hold a steady 6/9 bar through the whole extraction time? On my BDB with 19g Pullman 876 basket it holds 9 for a bit then degrades to 3-6 bar for the remainder. Is this standard?

With the Nurri lever espresso machine, I get much better and higher extraction with very light coffee when I do a blooming shot with a pre-infusion of 6 bar then with 3 bar. The pre-infusion takes also longer time with 6 bar, 40 seconds and 25 s for the 3 bar pre-infusion. When the cup gets 1,5 gram of coffee (the pressure is down to 3 bar), I let go the lever for a 10 bar shot. Total shot time 60 - 80 seconds My theory is that this is due to the rapid increase in pressure that the machine can provide with a large amount of water.

Now I wonder if you used a scace to have 9 bar at the puck and 6 bar at the puck , whether that would send it over the edge and make a difference . I’m assuming it’s around 8 -8.5 bar at the puck with 9 bar showing on pressurestat . My double boiler rotary shows 10 bars on stat for 130psi on the scace.

Thank you. I am wondering what would be the results on a Flair between 6 and 9 bars.

badabum badabang! thanks lance & keep it up ✌️

A little OT: How do you change the pressure in Linea Mini R; just on the flow when pulling a shot or do you use a blind basket always? -A happy owner of Linea Mini R

Interesting, thanks for sharing! What about testing 1 bar and 3 bar shots??

Lance, do you have any recommendations about grinders (or burrs) for lever machines? Which set is better for Argos? Thanks

You skimmed by it but the quakers in natural coffees is interesting. It would explain why from shot to shot it can be inconsistent at times for my coffee, often naturals.

Not minding budget. Would you recommended the Bianca V3 or the new la marzocco Mini? Thanks!

Why are we showing the decent doing the shots, I thought it was linea mini r? Do you think that the relatively high dose could be a factor, ie maybe an 18g 6 bar might be better than 20g 9 bar? Thanks for the video, very interesting as I drop my pressure on light roasts to 6 because that’s what we are supposed to do.

Is there any difference in setting the pressure via OPV vs affecting it with just grind size? Like if you set the OPV to 9 bar but ground coarse enough to at least start at 6 bar? Thanks.

In the voiceover, you indicated that most of the tests were run using La Marzocco, but in the video, there was plenty of Decent DE1 B-roll. Did you do some testing with the Decent? If so, it seems like the speculation about puck erosion rates could have been proved out one way or the other with the graphs from the Decent pulls, the data would be right there.

Is there any logic in holding the cup directly under grouphead to capture the espresso stream at a closer distance? Apparently the diving gravity affects consistency?

With the 0.6 mm giclure I guess the water debit is more reasonable than the 0.8. I lowered the pressure to get 250gr/per second as the machine arrived stock with nearly 490gr/sec. Shots improved dramatically in taste.

Thanks, Lance... So, if the taste and extraction are indiscernible between six and nine bar, would we consider using a lower pressure to lessen the strain on the machine components, thereby prolonging the life of the machine? 🤔

changing baskets (types of flow) instead of changing grind size to get desired flow rates can also be interresting no ?

1) Am I understanding correctly that you think the 9 bar tasted better because of the increased flow around the end when the puck gave out? I tested this at home with a washed light roast from Peru (from Elm in Seattle, which was pretty good) and had the same experience: the 6 bar was "grittier" and harsher than the 9 bar, but I wonder if this is because 9 bar is extracting less overall (thinking of that volcano graph in the turbo shot paper) and therefore just has less flavor (not necessarily bad) 2) I have seen that Flat Max in the background a few times now and now you're using it for your experiments. Is a review forthcoming? Big thanks for your work, as usual

I wonder if we should be discussing water velocity as well. You touched on this slightly when talking about the differing flow rates between grinds and setups. Velocity is the 3rd factor when considering standard flow hydraulics, if you have 2 pipes, 1 is 20mm diameter and 1 is 40mm, both have 50 litres per minute @ 5 bar flowing through them, whats different? the velocity. the water must move faster in the 20mm diameter pipe. If a course and finer ground coffee both had 2 ml per second @ 9 bar flowing through them, surely logic indicates the finer grind would have to have higher water velocity occurring? Higher velocity is more turbulent and exerts more friction, perhaps it could also be disturbing a puck more, carrying more fines with it and altering texture accordingly.. All just speculation from an amateur coffee enjoyer and ex irrigation system designer haha. What do you think?

Nice video Lance ! So if I understand correctly, 9 bar seems superior because of the "artificial pressure decline " vs more constant flow in the 6 bar shots. So if you have flow control machine, the pressure seems to be useless ( between 9 and 6) . the flow profile is more important like doing a tappering profile ? I understand correctly ? 🤔

I would love to hear your thoughts on 11 vs 9 bar, and the potential impact on channeling, as so many machines come set well above 10 bar. Anecdotally, when I dropped my machine from 10.5 to 8, my consistency improved. I fully acknowledge that this could be confirmation bias.

For me it's all about getting in an appropriate pre-soak with perfect pressure profile for that precision flow rate. Just observing how changes to those profiles impact the extraction indicate how important flow rate really is.

Now let's say that my puck prep is not very good, or my grinder is not great - then could I hope to avoid some channeling with 6 bar? Also, you mentioned naturals being less consistent shot-to-shot than washed coffee - was that comment about Ethiopian naturals, or in general?

In recent videos you often say that traditional pump machines try to remain at a certain pressure but is that true? From other videos (I believe also yours) I got the impression that they just have a certain water debit and in relation to the puck resistance they top out at a certain pressure (which might or might not be reached for very different fractions of the extraction time). Trying to maintain 9 bars would however imply pumping harder as it drops and increasing the water debit which I think traditional machines without any electronic profiling don't do, right?

Hey Lance! Is there a video planned on the new technique of Coffee Waving introduced by the German Barista Champion Felix Hohlmann? It seems to have a pretty big impact on the tasting notes. :)

I think it's crucial to bring milk into this study. Over the years my favorite espresso shots that were pulled were all tasting incredibly sour in even just the slightest amount of milk. If I ground finer and pulled longer, the beautiful delicate notes I loved about that espresso were nearly gone completely in the black espresso. The only way I could pull an espresso shot with intense delicate notes that both never folded under milk and tasted incredible as a black espresso was lowering the bar pressure from my typical 7.5-8 bars I've been using for years across hundreds of coffees and pulling longer shot times (faster shot times like I had been using make light espresso in milk not taste sour, but they lack flavor character especially in milk with vst baskets and specifically my workflow, this could be unique). The lower I go, the more intense and delicate flavors remain. I go about as low of a bar pressure as possible before the espresso tastes sour in milk, then I'll go up about .5-1 bar higher just to be safe. This is how I dial in. Granted, I'm using vst baskets and pulling shots for over 1 minute often with about 12 seconds of pre infusion on my mavam. I'm also using hopper fed beans or full dose feeding with wanted retention in my grinder above the clump crusher. If I slow fed In my bentwood I would not be able to grind fine enough for my beans to run through the burrs. This is highly specific, but this has worked wonders for me. I also know a lot of other shops using the mythos and hopper fed (commercial) grinders where they've found that lowering the bar pressure pulls incredible shots for both black and white drinks. Many of which had been shocked by the change. I should say that with these modern baskets, I can pull shots that blend well with milk and show origin character even at just 12 seconds pre infusion and literally as fast as about 8 seconds of 4-5 bar pressure with my ssp brew burrs 😂 I think the modern baskets are much more of a different story with white espresso. Though I do prefer traditional baskets with longer shot times for both black and white drinks if I'm being critical on flavor, but it's MUCH easier to avoid using these techniques and just pull fast shots with modern baskets at one grind size for nearly all coffees. I'll take that small flavor sacrifice any day for a high volume bar. Just thought I'd share my experience with milk based espresso in regards to your video. Thank you for taking the time to do this test! I'm glad more people will know that bar pressure for black espresso doesn't matter as much. Maybe we can see this topic of white espresso discussed soon? 🤩

Finally the MAX SSW is on the show!!

Do you think it’s easier to dial in for 6 Barr in comparison to 9 Barr? I have a 1zpresso hand grinder for my home espresso setup and idk if I’m ready to grind my light roasts finer in the morning 😅

I’m confused about the shot times. As I understand it, the grind setting was the same for both 6 and 9 bar shots. According to the theoretical model from the paper “Systematically Improving Espresso: Insights from Mathematical Modeling and Experiment,” I think we should expect the flow through the puck to be faster at higher pressure, when grind is held constant. A more minor point, I think we should also expect EY to be higher for longer shot times, if yield is constant.

I wonder what this might mean for us manual pullers. How might purposefully changing flow rate during a shot affect quality?

I started brewing espresso at home a year ago with the Flair Classic and I have always had an easier time using 6 bars. I remember watching James Hoffman refer to using 9 bars as “brewing on hard mode.” Once I tried a lower pressure, I was able to get shots dialed in. Before that it was messy lol

Is there a coffee subscription you personally recommend?

Man, some breakneck speed on your releases lately

Was there a reason why you used the Linea Mini instead of the decent? Using the decent seems a lot more precise to me and you could monitor flow, pressure, temperature etc.

i feel like these findings suggest that my cafelat robot is really one of the best machines that allows you to adjust the pressure based on resistance and flow rate 'on the fly' which leads to less wasted shots... as you can still get decent shots even if your grind size is off by simply adjusting the amount of foce applied to the lever arms

What about pulling the shots at a lower temperature also 125.6F/ 52C Doesn’t that make for a sour shot?

Hi Lance, wouldn't it make sense to get a multi group machine for your tests? I'm sure you thought of it already, but just asking in case you didn't 😄

I'm liking this new series of videos. Now how to translate this to my Robot :)

Purely anecdote and not data of course but having owned a Decent for 18 months after playing around, I settled on dynamic flow-controlled profiles which always seem to give me the most consistent, pleasant results. It's almost impossible to make a sink shot with them.

I use gentle and sweet profile on my decent which is pre infusion than 6 par and decline to 3 give me a very good shot

Random Q: where do you get all these cool cups? I recognize the Fellow one, but the others...

I'm a little confused at first in this, regarding the previous findings from Cameron et al. I guess in your case, you kept the grind the same, just limiting the pressure from the pump, whereas for the Turbo, the point is to go coarser and faster, which leads to higher extraction? So in other words, they tried something else and showed you didn't need 9 bars for it, while here you just tested pressure (relatively) in isolation?

Great stuff!

And 11 bar ? When i did maintance on my ECM giotto the man adviced me to set it on 11 bar. Is this good or must I set it to 9 bar