A month ago I was going along happily just brewing my coffee. Now, since I stumbled across your channel, I am sitting here looking up how to test the hardness of my water, running triangle taste tests, measuring the consistency of my grinds, and even home cupping. WHAT HAVE YOU DONE TO ME?

Making my morning coffee looks more like I'm cooking meth now

Laying in bed about to go to sleep but wishing I could just stay up and experiment with coffee all day.

Hello James, I think you have a very interesting experiment here. I am glad that at least some coffee experts are willing to test assumptions and shake (or break) old ideas! I believe the hard water bloom you observed has more to do with the pH of water than it’s hardness. This would be an easy one to experiment with, but first let me explain how I reached this conclusion. I am a chemical engineer and I have spent a considerable amount of time developing a process to convert biomass, such as wood, corn stover or bagasse, into more useful materials. Coffee (green, roasted, whole bean, ground, etc) is biomass too. All biomass contains basically the same stuff: cellulose, hemicellulose and lignin. There are other things in it, and to be sure in the case of coffee these other things are what makes coffee distinct and so flavorful. Yet, one-fifth of the mass of coffee bean is lignin. I did a series of filter-extraction experiments on lignin, which I had previously purified from woody biomass. It was clear that using water that was more alkaline in the extraction caused a dramatic blooming effect (swelling of grounds). In fact, a small increase in pH caused filtration to nearly stop (lignin became impermeable). On the other hand, neutral or slightly acidic water filtered through ground lignin without a problem. Lignin is a complex material that gives plant life its structural rigidity and protects it from the elements. I believe alkaline water makes lignin partially ionic, completely altering its filtration properties. Water hardness is not the same as water pH, but it is correlated, with harder water being more alkaline (higher pH). I would speculate that extracting coffee with hard water seems to increase blooming not because more CO2 is being pushed out of grounds, but merely because hard water affects the physical properties of coffee that have little to do with flavor. Indirectly, hard water makes filtration slower, which could lower the quality of the resulting cup of coffee. Cheers, love your videos!

Noticed James hiding his bandaged finger and now I can’t unsee just how well he hides it throughout the entire video. What a man!

James, the way you “set up” the brew during your ad was pretty cute. I would’ve enjoyed a bit more spoon sorcery, but this vid was still rad.

'...the next video on the channel will be the V60 video' *screams in disbelief*

As a control specifically for the bloom with harder water, you could bloom with softer water, and add the volume of harder water immediately after the bloom. Extraction between the two brews, and acidity of the total volume of water should be comparable, so then it's just the bloom.

A fairly sciency answer could be ionic strength I.e. in hard water there are generally more ions. My correlative hypothesis. During the blooming process some CO2 release from grounds becomes dissolved in the water prior to off gassing and some CO2 remains dissolved. The presence of other ions in the hard water cannot be displaced to gas and inhibit CO2 solubility making it off gas faster I.e bigger bloom. This could potentially explain the acidity change as well less dissolved CO2 could result in less formation of carbonic acid.

My old man worked in marketing for a coffee company in San Francisco in the late 60s right out of collage. They were making canned ground blended coffee, but the executives enjoyed drinking fresh ground single source coffee and blends to experiment with the flavors. My dad suggested they try selling little one pound bags of fresh roasted whole bean coffee so that customers could enjoy the same quality they drank in the office and he got laughed at. They told him the unwashed masses weren't sophisticated enough to appreciate coffee in that way. Now look how we buy coffee.... True story.

This is definitely one of your best uploads. The editing was superb, the soundtrack was beautiful, and the way how you threw in your ad in the "setup" process was genius. Proud to be a patron James, keep up the great work!

I liked this video for two main reasons, 1 - your style and apresentation are very pleasing to watch, good identity I always come back to the channel. 2 - When you apply the cientific thinking into the everyday situation you are making science at its finest, good job.

I started following your videos after you confirmed my position against swirling espressos. I am learning a lot with your work and curiosity. For the last three weeks, I watch one of your videos while I brew a pour over for breakfast. Thank you!

Another video with dope music from James the Demystifier

I love all the old footage at the start of this video

I feel like James Hoffman fills his videos with as much cinematic shots as possible and I love them

right off the bat James, hard water is going to affect PH which in return affects acidity, so there's part of the answer as to why one had more "acidic bite" over the other.

Love the nerdiness, love the imagery. Oh, and you should consider doing voice work, audio books, etc.

all the science and theories aside, brewing part of the video was so beautifully done. really enjoyed it :)

Love the intro of this new series! Our roastery is in a area of surprisingly hard water (for Dutch standards), but it is coming from high quality reserves of ground water. We filter (and soften) the water going to our espresso machine, but for pourovers, I have mixed feelings. Not all our origins necessarily benefit from using filtered water. But in our case we guess that the filtering is removing "nice" minerals and perhaps flattening out some coffees... but my guess is that we are fortunate and our tap water is high in magnesium and other minerals, but not in bicarbonates. Coming back to your experiment, as a business serving V-60's, we go frequently through the process of blooming and brewing with different waters due to logistics and rush periods. Mostly we refill the kettle with the 95C tap that goes through the filter, sometimes I fill it from the normal tap and let my bonavita do the heating (it doesnt fill nicely under the other tap ;-)). When doing multiples pourovers, I sometimes run out of water after rinsing filters and blooming (with hard water), and I quickly refill a kettle from the filtered tap. Even then, I personally dont notice an improvement. For delicate teas that's another story altogether and we only use filtered water.

Love the concept! This is like a deeper dive into coffee. I do know that type of water we use could affect brewing that is it. Heard of soft and hard water ('coz I purchased your book, haha) but never really understood it thoroughly. Looking forward to the next episode as always! 😊

almost relieved to hear after many years brewing with soft Edinburgh water and being vaguely concerned it never seemed to bloom like the youtube videos 😂 ... Great intro btw 👍

I tested this, James, and each time I scoured my press pot with metal cleaner so it was pristine without any oil residue, used separate clean metal filters + paper filters (I use paper as well as metal as the inclusion of paper cuts down on coffee "silt" and makes the cup more delicate to me), same extraction times, and the same bloom time. Hard water for the initial bloom makes a noticable difference, and as I don't like really acidic coffee, proved good to me. Also, bloom time matters a great deal...started out at 20 seconds...wasn't enough. Increased to 30, as well as stirring later on.

"Let's uhhh let's do that then" this is the English delivery that keeps me coming back every vid.

I definitely noticed bigger bloom/co2 with harder water. For example when I travel to USA there are very hard water in some states. Sometimes I have to downscale the amount of coffee I make in my Aeropress because it "blooms over". Inverted method: 16g coffee and 240g water works fine until the water is hard and I spill all over the kitchen counter...

I don’t know what a bloom is, so thanks for starting with that.

Love it. Everything: intro video, hypothesis, experiment, conclusions, the grand question "what if?". Thanks!

I am so excited for the v60 video!!!!

James - there's a cool phenomena you might want to unfold. Dripping a little cold water in, towards the end of a Greek coffee brew, produces a tasty white crema. I could never understand why. The same effect is also achieved through lightly flicking a spoon around the edges, at the end of the brew. Wish we could chat all day about Greek coffee prep but for now I think this may be a cool angle for your science series.

This makes sense because the acidity in coffee is probably reacting with whatever pH buffers that are contributing to the hardness of the water. Edit: Lack of acidity confirms my suspicions, the extra bloom is more than likely a byproduct of the acid-base reaction that is taking place with the coffee and buffer.

Hi James, awesome idea for a series. As a chemical engineer doing his PhD on delicate chemistry this series certainly blends my passion for coffee with my curiosity to discover the chemistry behind it. This particular video touches upon an issue I had while brewing. I live in Portugal in a region with typically softer water, but have been living for the last few months abroad in a region with clearly harder water. Although I didn't notice the difference in bloom volume, I did notice that brewing with harder water does tend to overextract and, additionally, mask the finer aromas of a particular batch of coffee. What is your opinion on this? Your brewing experiment here was certainly interesting, but what about adding a third brew with just hard water and compare the results? I'd love to hear your thoughts on this. Keep up the great work!

James, I think you should start with distilled water and add minerals to it creating some very hard water. Then mix that water with distilled water to achieve any ppm level you wish. Then you can test many different levels of hardness and compare. I use the following recipe: Potassium Bicarbonate @ 0.1g per 300 grams Distilled Water Magnesium Chloride @ 0.5g per 300 grams Distilled Water Calcium Sulfate @ 0.4g per 300 grams Distilled Water To just say use soft or hard water doesn't work for me, as there are too many variables. I have been using between 100 ppm and 150 ppm water to make espresso, using my Flair Espresso Maker and Kinu M47 hand grinder, and am pleased with the result. I find it amazing what one can feel when using all manual devices, as you don't get the feedback when using powered machines. I roast my own coffee, and even find differences in the espresso making experience because of the roast level or the coffee seeds themselves! With my tools I can dial it in very nicely, but there are still differences even when trying to do everything the same.

This is a great science outreach video!

Oh wow, we need more of this stuff. We have a lot of pieces of information that we kinda have to put together to see what REALLY makes difference in coffee brewing and other areas in general. So, thank you James! Keep it up

So happy to have read the description. Been waiting quietly and patiently for a V60 video for years!!

Im not even that interested in coffee, but hearing you talk about it makes it seem like the most interesting thing in the world. Love your enthusiasm.

This really shows the genius of the espresso machine: soft water, with the degassing taking place during extraction, but overcome by pressure to force the water close to the particle to extract a well rounded shot. It's like realizing that someone long ago ate the first artichoke and discovered the delicious heart, but you're still trying to figure out how to get all that hairy crap off of it first.

Making coffee at the high end is definitely part art and part science. However I am very impressed with James' analytical and critical thinking. His pursuit of excellence is very admirable.

I love the intro. Also the beautiful close up shots during the pour over, although I have to say, interfering with the blooming phase by swirling ruined what could have been such a beautiful sight.

So we go even more geeky now? Love it!

I primarily use coffee as a companion to certain things I like to eat with it, breakfast, pastry, etc. I use tap water with drip and our hard water does fine for that, I use a refillable Keurig cup when I need speed, and I have to use bottled water for that, so the latter for just drinking unless I'm pressed for time for using with food

Hey James, your videos are great!! I love coffee, and your videos are very informative, I watched your videos on blooming and decided I should give that a try with my percolator drip coffee and turns out it makes your coffee way better from a percolator dip style coffee maker. You should talk about that! Just interrupt the brew after just submerging the beans in hot water then let it bloom and continue your drip.

I am all for this series! Love this idea, thanks for the hard work!

Everyone: Please pour over video. James: ok, ok, pour over basics: Bloom... Oh boy...

The Hoffman effect is real. Can't believe I'm experimenting with hard water and soft water blooms now while most of my peers wouldn't know the definational difference even becuase neither did I.

I love the "nuclear physics" type opening. I like to think at this stage I have at least an OK grasp of cooking, yet making consistently good coffee in small batches continues to be a daily struggle :D

A collab between James Hoffmann and Peter McKinnon would be fire🔥🔥🔥 Both of you share the same love for coffee yet you both are so different.

Love this, can't wait to see more. The one feedback, i'd love to see them longer!

Did you hear about Water for Coffee: Science Story Manual book? Authors of this book made some research about how different ions in water change the way coffee extracts. There are also some vidoes on YT from authors' lectures.

I experiment with V60 all the time. First, I split the brew into 4 cups (one for each pour or "pulse"). By putting my bloom water in one (heated) glass vessel and each subsequent pour in another, I can test flavor at each stage and measure TDS. I've fussed with all manner of things. Increasing temperature each pour, for example, brings out more sweetness and aroma from some naturals grown at high altitude. Basic Steps: Preheat four individual glasses with boiling water (dump hot water right before brewing into each vessel) Brew one pour into one cup, Swap the next cup onto the scale while water drips through. Tare. Pick up the V60 and move it onto next cup just before adding next pour of water Repeat those steps until recipe is complete.

Hi, James! I tried to set up your experiment, but with one more cup: mix together hard and soft water. Same amounts like in cup with hard water bloom. Taste quite similar to cup with hard water bloom.

I'm going to love this series

Beware of the different is better phenomena. Interesting suppositions.

Hi James, really enjoyed this video but I have one major request for future experiments: please taste them blind! I cringed a bit when you explained the effect that the hard water was having and how it aligned with our preconceived notions of hard water brewing. In the future, if you were to taste the coffees without knowing which one was which, your stated results may be more indicative of the coffees' differences rather than our preconceptions. Thanks a lot and I'm looking forward to more of these in the future!

I'm only 10 seconds in and the shot of a guy gently wank1ng a coffee bag made my day :-) - 0:10

A great experiment and one that I’ve been wrestling with in rural Missouri in the states. I’ve noticed that I prefer my personal well water over the city water. So I experimented with distilled, Third Wave, City water, and Well Water. Now I water to do the same test while examining the bloom.

I love the cuts in the sponsor messages, where you add a new component for coffee brewing each time. Very cute and subtle.

The look of evil genius on his face when he proposes blooming with hard water and brewing the rest with soft water

Here's an idea! One of these episodes could be a collaboration with Cody's Lab or NileRed or someone of that nature, that would be awesome! Also...you might get a load of new subs, the amateur scientists who watch those video, I can guarantee, are avid coffee drinkers ;)

The coffee industry in 2030: all espresso machines have two water lines and shots are pulled using "hardness profiles"

Does more blooming foam actually equal better blooming? To me it just seems to say something about the foaminess of hard water. It's probably the same reason why you need more soap with hard water. Cursory google search suggests different surface tension.

Could dump the bloom water before brewing the rest. Really interesting video. I'd never thought about this. :)

1. Hard water bloom, hard water brew 2. Hard water bloom, soft water brew 3. Soft water bloom, hard water brew 4. Soft water bloom, soft water brew 5. Mixed water bloom, mixed water brew 6. Hard water bloom, mixed water brew 7. Soft water bloom, mixed water brew 8. Mixed water bloom, hard water brew 9. Mixed water bloom, soft water brew 10. Finished :)

Great video! It would make sense to taste the coffee blind though, to remove the possibility of unconscious bias.

LOVE LOVE LOVE this series!!!

James, you’re an absolute pro on-camera. I noticed a small bandage on one of your fingers. You carefully wrapped that finger inward for the entirety of the video, so it wouldn’t be a distraction to the viewer. I guess you want to give the audience consistency with your image? Whatever the reason, you’ve got me wondering what all goes into making such crispy, clean, professional content.

How does this channel not have at least 1mm subscribers? James is a legend.

I found this video at the top of the reaults for my search “coffee bloom phase”, and I’m really trying to answer “why bloom coffee”. Can you do a video on just this, or recut existing videos on this? I’m sharing the information with others and appreciate the thoughtful, composed, informative, and persuasive presentation of James’s videos

Now this is the type of content I've been looking for, will run some experiments!

James, my theory is that hard water contains sodium as well as sodium salts. This increases thermal conductivity of water. This is turn makes the bloom faster (gas release rate) because heat is transferred from the water to the grounds more efficiently. On the other hand, hard water does not produce or hold foam as soft water, so the CO2 bubbles that form the clusters of foam tend to rise faster and float over the water without mixing with it. This ends up showing a denser bubble cluster that floats over the liquid giving the impression of a higher gas volume at same ATM pressure.

Good experiment would be to compare: Bloom with hard water, then brew with hard water, Bloom with Soft Water, then brew with hard water, Bloom with Hard Water, then brew with soft water. Also might as well do Soft and Soft! So you got basically all the combos to compare. I guess you won't know what's really contributing to what (actually maybe you would?) maybe instead of doing a small bloom and larger pour, split it so it's 50/50 with a good minute pause or so between the bloom and main pour (which are now equal amounts). Then if Soft then hard is the basically same as Hard then Soft, you'll know it's probably the overall hardness amount contributing to the extraction efficiency and not the hard bloom specifically. I'm guessing that would be the case, and soft and soft would be under extracted tasting, where hard and hard would be over extracted. I found in general using higher mineral content (or at least using different Third Wave Waters, vs also pretty hard filtered Tap water) the TWW / Mineralized water made extraction more efficient so I had to lower temperatures to avoid over extraction.

I suggest seeing how the concentration of CaCO3 (Calcium Carbonate) affects the bloom of the coffee. When Calcium Bicarbonate ionizes it turns into a Bicarbonate ion which will probably turn into carbonic acid instead of CO2. On the other hand the Carbonate ion of CaCO3 has a higher likelyhood of turning into CO2. Forming of Carbonic acid from Bicarbonate ion HCO3- +H30+ ----> H2CO3 + H2O Forming of CO2 from carbonate ion CO32- +2H+ -----> CO2 + H2O *The Carbonate ion can also turn into carbonic acid Sorry if I wasn't clear when writing the reactions, I can't write in sub/super-script on a youtube comment

I love how you hid a V60 tutorial in here ... swirling the bloom, eh? ... you must have the older V60 papers ... you do! ... the fluff on those grinds is incredible

Every video's intro music just makes you wanna go watch Stranger Things 👌

Fantastic production quality, love watching your videos during my lunch-break

Actually did this type of experiment a while back. I use tap water typically, its a little hard but the TDS and mineral content is very good. I also purchased some of the third wave water stuff to try, out of curiosity. While the water did taste softer and a little tastier in my opinion and taste, it actually flattened out the coffee quite a bit, almost made it duller. It had a little bit of the prickly acidity that you mentioned with the soft water only brew but beyond that it just didn't taste as full. Course I could be just conditioned for the harder water at this point. The hard water just tasted fuller and had a larger range of notes. I will have to try the blooming with hard water and brewing with soft water some time. My real question is does it matter all that much the size of bloom when brewing?

I love your videos! Professional, lovely and practical! You are my coffee guru!

Can’t wait for more!!!

Finally get to see you doing a pourover. I have a no coffee from the late afternoon onwards rule, and those stunning visuals have me eager to run back to my V60 and brew a cup up. Thanks James.

I love coffee. I'm learning more and more.

You should make sure that all the water running through the coffee has exactly the same composition. So, same amount of bicarbonate in total. So if the water for the bloom is harder for one brew, the rest of the water for this brew should be accordingly softer. So in the end both brews contain the same "water".

Surely added bicarb would interact with dissolution of CO2, no? It would seem to make sense to also test with other softeners (citrate, borate if you're adventurous) and with distilled water.

We need a fast car chase in an urban European setting in an Italian sports car followed by a Bond like spy having coffee with a bad guy who uses coffee as a cover for his sinister activities yet the prep and serving and drinking of the coffee should be emphasized scenes like the pastry scene in Inglorious Basterds.

I’ve long speculated that the main benefit of blooming has nothing to do with the the gases coming off but simply getting all the grounds wet. If you do a pour over on dry grounds most of the water will go though before most of the grounds getting a chance to participate.

My god arent you the biggest coffee nerd on youtube. I love it

Weird Coffee Science topic recommendation: the fleeting magic of delicious non-specialty coffee. Why does some diner/donut shop/gas station coffee taste surprisingly good, when all of them are brewing with no particular concern for the taste?

I think we could learn a lot from beer brewing and their deep study of the water.

Okay James, I have an experiment for you to try. Something a bit out there. What if you roasted some single serving coffee sous-vide style? In this way you could even pre-grind (grind your beans before roasting) and “roast” them in their container (glass or steel or high temp polymer?) in an oil bath. A slow temperature ramp would ensure very even, consistent roasting, and proper containment would mean no loss of aromatics. Just make sure the CO2 pressure won’t pop the container you choose while submerged in hot oil. Could sous-vide coffee roasting become the next improvement vs. air roasting? Nerds like me want to know!

Work with Socratic Coffee. Their science + your delivery and audience = WWWOOOOWWW

Just a thought, (More like a rabbit hole) but I'm curious to see how the test of combining hard & soft water in different combinations throughout the brew can affect different factors like Density, Roast Level, Processing. Could lead to some interesting results.

YES! I have been waiting for a pour over tutorial from you for so long

This. I like this. Absolutely brilliant idea for a series and also community-involved activity.

I think doing videos like this is a great new direction for you channel. Very interested to see what you come up with next!

If you think the primary factor influencing the bloom is presence of bicarbonate, I would suggest making a series of bicarbonate concentration solutions using deionized water. This way you could focus specifically on that variable and see how close your final products come to what you experienced in your initial comparison. I would also suggest sending water samples off to a lab for content analysis to get a fuller picture of what is in your hard water source.

Love it. Thanks for starting this series!

My man, you should really consider doing documentary commentaries...your voice is so soothing!!

Take 1 campfire tin can coffee percolator add 1 whole egg (shell and all) smashed in the bottom of percolator. Add your desired amount of ground coffee to the egg mixture and stir this mess together within a couple of stirs you’ll have a nice coffee paste. Just add amount of water to conform to your expected cups of coffee. Place on campfire and perc until the desired color of coffee is reached. Remove from campfire and pour a delicious cup. The coffee grinds remain in the congealed glob at the bottom of coffee pot.

A shop where I worked made cortado-size espresso drink where the shot was floated over cold milk and simple syrup. The espresso floated in different ways across the many dairy and non dairy milks and milk temperature also played a role. I think it's probably a sort of basic matter of density and maybe fat content but I'd love to see you lay it out in this kind of video

It's always a pleasure to watch your video

Simply amazing watching your thoughts and experiments