Water, Pt 1 — Alkalinity, hardness and why it matters

James Harper:

Good water for coffee. Water makes a noticeable difference to the flavor of coffee. We all know if you want great coffee flavors, you gotta have good water for coffee.

But figuring out good water for coffee? It's hard. It's complicated.

But today, I'm giving you a guide. A simple walkthrough guide to help you get great water for coffee. Now, if you know me, this is not the sort of episode I would ordinarily make on Filter Stories.

But I decided to make it because I had this wake-up call when my friend and fellow podcaster, Lucia Solis, she has her own great podcast on coffee processing and fermentation on the farm. She and I were chatting on Zoom.

Lucia Solis:

And we're just, I just had my first sips of my first coffee of the day, so I'm just barely booting up.

James Harper:

FYI. And we've been chatting a lot recently, because we're planning to release a series on coffee farming next year. Stay tuned for that.

But during those chats, she mentioned how the water on the farm where she lives in Guatemala, that water had suddenly made her coffees taste bad.

Lucia Solis:

My partner, Nick, and I, we were preparing our coffee. And we've been having this coffee for a long time. We're very familiar with this coffee as part of our background.

We produce coffee, as well as get to taste coffees from all over the world.

James Harper:

So you live on a coffee farm in Guatemala.

Lucia Solis:

That's correct. I live on a coffee farm in Guatemala, and we have been producing coffee here for three different harvests. And we're doing quality control on this coffee.

I know this coffee really, really well. And one time when we were trying this coffee, it just tasted so off. It tasted chalky.

It tasted flat. And I was like, this is not our coffee. This is not the coffee that I remember, that I recognize.

I didn't know what was going on. And then Nick mentioned, well, let's look at our water. And so that's when we decided to go down the rabbit hole of water.

And I was just sharing it with you because I felt so embarrassed in that, you know, coffee is mostly water. We know it's incredibly important. And even me, a coffee professional of 10 years, had not solved this water problem.

James Harper:

A Q grader.

Lucia Solis:

Q grader. Last Q grader. Wow.

And I had not solved this problem. I hadn't stabilized this variable. And then when I was looking at it, I was like, but now where do we go?

James Harper:

By the way, a Q grader is someone who's specially certified to objectively assess coffee quality. But anyway, this here was my wake up call. Wow.

If Lucia is struggling to figure out what good water for coffee looks like on her farm, I just couldn't imagine how many other people are struggling too. And the thing that's crazy, I couldn't really believe was like, a simple guide for good water for coffee doesn't exist anywhere on the internet? As far as Lucia could find, no.

Tell me about, how did you go about figuring out what was the best water for your coffee?

Lucia Solis:

That's a great question. Because I, yeah, it's like, I know this is not good, but I don't know what is good. So I have this vacuum.

I have this emptiness. And so the thing that I always do is, okay, let's listen to more podcasts. Because that's my favorite way to get information.

I'm much more of a podcast person. So then, of course, I started listening to all of the podcast episodes that I could find that mentioned water. And I had lots of information.

I was flooded with really cool facts, but I didn't know what to do in my kitchen right now.

James Harper:

And I got to say, I felt, when you told me all that, I felt kind of ashamed myself. Because I had made an episode about water for coffee.

Lucia Solis:

And I listened to that too.

James Harper:

Right. And it didn't help you at all with this question, right?

Lucia Solis:

I was still lost. Yes.

James Harper:

This is the crazy thing. It's not just podcasts where there's this vacuum. Because after you told me that, I also went on the internet to try and find like a good, simple guide for figuring out how to get good water for coffee.

And I couldn't find one. All the guides like immediately swamped me in complexity. And I'm like, hold on, hold on.

It doesn't have to be that complicated. Because I know what the right answer is. Because to make my episodes about water for coffee, I had to dive down into the science myself.

And after spending hours speaking with the world's leading coffee scientists, chemists at BWT, my partner sponsor for this episode, going to visit their factory in Monsey, Austria, doing coffee water tastings in Copenhagen, and doing water analyses in their offices in West Germany. Like I know what the answer is. And I'm going to just tell you what that answer is in this episode.

Lucia Solis:

Awesome. I really need to know this. Okay, James, how are we going to do it?

James Harper:

Okay, so the end game here is I want you to be able to know what is in your tap water, and then how to treat that water to get it to where you want it to be. But first, to get there, I have to explain the two things that really, really matter when it comes to water for coffee, right? And that is the alkalinity of your water and its hardness.

Lucia Solis:

Yeah, and I think that's definitely what's been missing is that we get so distracted by how interesting it is. But we forget that we don't have a foundation. So we're like jumping off the deep end, but we have nowhere that we were jumping off from.

And so I think that being able to talk about the basics, it's the thing that will actually make a difference.

James Harper:

Absolutely. Now, let me explain to you my plan here in a bit more detail. So in the first half of the episode, I'm going to explain to you how alkalinity changes coffee's acidity.

And that matters because, you know, we in specialty, we love acidity. And then I'm also going to explain to you how the hardness of your water really matters too, because it affects how quickly lime scale builds up in your espresso machine boilers, or your kettles, or your brewers. And if it gets out of control, it could be expensive to fix.

So in the first half of the episode, I'm going to explain those two concepts. And then in the second half, I'm going to show you how you can measure the alkalinity and hardness of your tap water. I'm then going to show you what the SCA, the Specialty Coffee Association, recommends is like good water for coffee.

And then I'll explain to you like what you can do to treat your water. But I can't explain how you should treat your water until we've gone through all these steps.

Lucia Solis:

Sounds great. Can't wait.

James Harper:

I'm James Harper, and you're listening to Filter Stories, the untold stories hidden in a cup of coffee. And this is my third series on the science of coffee. And Lucia, would you like to say the tagline?

Lucia Solis:

Sure. A journey into coffee's hidden microscopic secrets.

James Harper:

All right, Lucia, let's kick into things. First up, I want to explain to you the concept of alkalinity, how alkalinity kills acids in your coffee, and why that's not a good thing for, you know, you and me who like to drink specialty coffees. First up, I'm going to show you how your coffee changes when you increase the alkalinity.

Now, Lucia, you're a former winemaker, so I'm sure your cupboards are full of chemicals.

Lucia Solis:

I feel like that's a judgment on my personality, but yes, yes they are.

James Harper:

Do you have something in your cupboard called bicarbonate of soda, also known as baking soda?

Lucia Solis:

I absolutely do. Yes. Also because I have animals and I need that neutralizing power of baking soda for cleaning.

Right.

James Harper:

Okay. So Lucia, it's morning for you. You have a cup of coffee in front of you.

Can I ruin your coffee for you, please?

Lucia Solis:

Oh, I was not prepared for this. This is my vulnerable first cup of coffee in the morning. I am not prepared to ruin this coffee.

And I have to tell you that the coffee that I'm drinking is particularly beautiful. It's a coffee from Kenya that we did as part of our fermentation workshop. So this is a coffee that we have made, that I made with my own hands, that we have brought back to Guatemala.

And we have like a precious little stash that Nick is like roasting on demand because we love the acidity. I love the brightness of a Kenyan coffee.

James Harper:

Great. I can't wait to ruin it for you. All right.

So I want you to sprinkle in just a little bit of baking soda. And what that's going to do is increase the alkalinity of your coffee.

Lucia Solis:

Well, I'm going to take one more good sip. Okay. All right.

I have my baking soda right here.

James Harper:

Put a pinch.

Lucia Solis:

Yep. Oh, this hurts. All right.

There's a pinch in there. I'm going to stir it in.

James Harper:

Okay. What does it taste like?

Lucia Solis:

Wow. That's gross. That's gross.

Hold on. I'm going to pull my partner Nick in. He's our helpful assistant.

And he just tried it as well. And I'll just describe his face is just despair. His face is just fallen.

Nick, what do you taste?

Nick:

It tastes like old coffee. Wow. Like it tastes like old diner coffee that's been sitting in a hot carafe for two hours.

Whoa.

Lucia Solis:

Flat, stale. Okay. I'll take one more sip for science.

There's no more fruit left. So this coffee was bright and had a lot of fruity characters. And now there's nothing.

There's nothing left. It's just like brown water. It just tastes like lukewarm brown sock water.

James Harper:

So I ruined your coffee, Lucia, because I wanted to show to you how important acidity is in your coffee. When you added that baking soda, you increase the alkalinity of your coffee. And what that's done is reduced the acidity.

And that's how big a difference acidity makes in our coffees. As soon as we don't have acidity, all those beautiful notes of berries, fruits, they disappear. For you and me who love specialty, acidity is great for coffee because it interacts with aromas to give us the complexity that we love in our coffees.

And now you're tasting how bad it can be when you remove that acidity. That's why for us specialty coffee lovers, the alkalinity of our water really matters. We want water with low alkalinity because we want the acidity.

Lucia Solis:

But James, what is alkalinity?

James Harper:

Ah, okay. Good question. So the concept of alkalinity was explained to me by the coffee scientist Samuels Marquet.

Samo Smrke:

He said it's how strong one solution is able to neutralize an acid. So if water has high alkalinity, it means that it will neutralize the acids in our coffee.

James Harper:

And I think to better explain it, let's first imagine water which has almost zero alkalinity. So imagine we had a glass of very soft water. This is water which has very little stuff dissolved in it, okay?

So let's say you brewed your Kenyan coffee with this water. What would happen is that you would extract the citric acids out of the beans into your water as you brew it. And yeah, those citric acids would make your coffee acidic.

They'd be floating around. And then when you taste it, ooh, that's acidic. But let's say, for example, that your water had a lot of stuff dissolved in it.

It was hard water. Now what you find typically in hard water is actually the same stuff you added to your coffee. Hydrogen carbonate, which used to be known as bicarbonate, hence bicarbonate of soda.

So yeah, hard water has a lot of hydrogen carbonate, which is the same stuff that you added when you added baking soda. And what that hydrogen carbonate does is it attacks acids and neutralizes them.

Lucia Solis:

Interesting.

James Harper:

Right? So let's say, you know, you're brewing your Kenyan coffee with this very hard water, which has a lot of hydrogen carbonate in it. What happens is as you extract the citric acid into the water, the hydrogen carbonate comes along and bam, neutralizes it.

And so these acids, which would have made your coffee acidic, they've been destroyed. And so your coffee isn't acidic anymore. And so the amount of hydrogen carbonate in the water, that is alkalinity.

Water with a high alkalinity has a lot of hydrogen carbonate. And that means you can have a lot of acids in your coffee, but along comes that hydrogen carbonate and boom, destroys them all.

Lucia Solis:

Right. So I get it. When adding the hydrogen carbonate to my Kenyan coffee, I understand that all of that additional alkalinity was kind of binding and neutralizing my acidity and my coffee tasted terrible.

But this was an extreme example. We were adding a whole pinch, you know, something I bought at the grocery store. Is this what's actually happening in our tap water?

Could there be that much hydrogen carbonate in our tap water affecting the coffee?

James Harper:

No, not as much as you put into it, but tap water can still have a lot in it, right? To the point where the flavor of the coffee will change.

Lucia Solis:

So how much could it change it?

James Harper:

Pretty dramatically. And I know this because I put it to the test. I did a taste test in Copenhagen where I looked at local tap water from Copenhagen, which is really, really hard and contrasted that same tap water, which had been through a BWT filtration system to remove a lot of hydrogen carbonate.

So basically this is a comparison of two waters with very different levels of alkalinity. Tap water has very high alkalinity, the filtered water, very low alkalinity. And the differences in acidity were crazy.

Tell me more. Testing one, two, three, testing, testing. Okay, so last year, World of Coffee, Copenhagen.

I'm at the BWT stand and we've organized a water tasting with a world barista champion.

Boram Um:

My name is Boram Um, born and raised in Brazil.

James Harper:

I had the privilege of meeting Boram Um, who himself is a coffee producer like yourself. And he had two coffees he wanted to test.

Boram Um:

I brought coffees from our two farms.

James Harper:

And we're going to try Boram Um's coffees with local tap water and the BWT filtered water. And then we invited lots of roasters.

Boram Um:

I'm David from Shanghai, China. I'm Mohamed from Sustain Coffee.

Lucia Solis:

I am Oran Seletar.

Nick:

And coffee educators. I'm Denis. I'm a coffee trainer and part of the quality team from Belco.

And judges.

Andrew Tolley:

My name is Andrew Tolley. I am a left Q grader, a sensory judge in the Barista Championships Brewers Cup.

James Harper:

And they all very kindly lent me their time to taste the same bag of beans, ground up, but with different waters served.

Andrew Tolley:

So what did they say? How big were the differences? Between B and C, it's quite stark, particularly in the acidity.

James Harper:

You know, everything was anonymized. Nobody had any idea what the waters were, what the coffees were. And what everybody said was how coffee C, which was the filtered water, right, which had a low alkalinity, as in it had lots of that hydrogen carbonate taken out, was beautifully acidic.

Andrew Tolley:

To C, you get this sort of much higher intensity of acidity.

James Harper:

Yeah, so C, the acidity went way higher.

Boram Um:

On cup C, you can see that super high acidity coming out. Very citrusy, very lemony, very juicy.

James Harper:

And then the Copenhagen tap water, coffee B, right, this is water straight out of the tap, which naturally has a lot of hydrogen carbonate. It has a very high alkalinity. It was the same coffee, but the acidity was gone.

To B, you get that mellow.

Lucia Solis:

The second one was a little flat.

Boram Um:

B is more muted. B, you can just see everything muddled and muted. Really hard to find acidity and the characteristics of the coffee.

Lucia Solis:

Okay, wow. So I can hear, I can see that tap water can make quite a difference in the flavors that people are perceiving, especially tap water that's hard is even worse for the flavors and that it can just kill the fruitiness, the acidity. But this makes me think that maybe we want zero alkalinity, that we want to get to very soft water.

So could the answer be that we just, for me on the farm, should I just be removing all of my alkalinity?

James Harper:

No, because there is such a thing as too much acidity. I don't know if you've ever tried a coffee with super, super soft water and the acidity was almost like mouth puckering, super sour. It's just overpowering.

Lucia Solis:

Yeah, I think at the time I didn't realize it was because it was super soft water, but I do remember that distinct feeling of trying a coffee that was just so acidic. It was completely out of balance. First I thought it was the coffee and then later I realized, oh no, it was using really soft water.

James Harper:

Right, yeah. So this is just like Goldilocks. You don't want too much alkalinity because it kills all the acidity, but you don't want zero alkalinity either because then the acidity is too sharp.

What you want is like that perfect Goldilocks middle ground, just the right amount. So Lucia, that's the flavor side. We're done here.

We're now moving on to how water affects equipment.

Lucia Solis:

Wait, wait, wait, wait, wait, James. We're moving on already? We haven't talked about minerals at all.

I read so much about minerals. What about our magnesium content? What are we going to do about that?

James Harper:

Yes, minerals definitely matter, but anybody in the water world would argue it doesn't matter as much as alkalinity. Alkalinity is like the major thing we want to get right first. The biggest thing.

Minerals have a much more subtle effect. What I'm trying to do in this episode is get you big strides into great water for coffee, and minerals are just not going to move the needle as much as alkalinity.

Lucia Solis:

Well, that's actually a huge relief because I'm not over here trying to become a water expert or a water nerd. I just want to have good tasting coffee. So if you tell me that minerals are something that I can kind of put on the back burner and just focus on my alkalinity, I think that's a win.

That's a win. Happy to hear it.

James Harper:

All right, coming up next. The other really important concept we need to understand for water for coffee, and that is the hardness of our water. All right, so we've just looked at how the most important thing in terms of the flavor of your coffee is the alkalinity of your water, which is like how much hydrogen carbonate there is to neutralize the acids.

Lucia Solis:

Yeah, and you want to have it really low, but not zero.

James Harper:

Yeah. Now, the second really important concept is the hardness of the water. And this matters because hard water produces lime scale.

And that's bad for our coffee equipment because it gunks it up, makes them less efficient. It can stop them from working and sometimes expensive to fix. So Lucia, how do you make your coffee?

With a kettle?

Lucia Solis:

I do. I have an electric kettle.

James Harper:

How's it looking? Is it looking a bit gunky, a bit chopped up, a bit white?

Lucia Solis:

I would say no, but I would also be embarrassed to show it to you.

James Harper:

Go on, show it to me.

Lucia Solis:

I think there is some residue, some chalky residue at my kettle, yes.

James Harper:

I can show you my kettle and you'll see the same thing. I live in Berlin, notoriously hard place for water. So your kettle, my kettle, they both have lime scale.

Now, lime scale is formed when water, which is hard, as in it has a lot of stuff dissolved into it, this hard water has two specific things in it, calcium and hydrogen carbonate, which is also the thing that kills acidity, as we've heard earlier. So what happens is that when we boil water at high temperatures, calcium and the hydrogen carbonate, they react together. And before these things were just swimming around, you know, dissolved in the water, but at high temperatures, they fuse together and become a solid.

They become lime scale and they get stuck to our kettles. Now we'll see, you know, our kettles, they don't look too bad in the grand scheme of things, but like, can I show you how bad lime scale can really get? Like if you boil hard water a lot and you just let that lime scale accumulate and accumulate, can I show you like the worst case scenario?

Lucia Solis:

I don't know, James. Last time I trusted you, you made me ruin my coffee. I don't know about the second time.

James Harper:

Rainy day, the Austrian mountains all around us with the clouds whispering in between. So back in September, I went to Montse, Austria to BWT's production facilities. And you know, I got a tour of the factory floor, you know, where they make all their water filtration kits.

And then in a side room, they showed me the testing they do. Get out! It's like someone shot it with a bullet.

Yes. It's cracked and exploded. Yeah.

And there's one specific test they do. This is a real life test. Where they basically boil really, really hard water for days on end to simulate what would happen to an espresso machine boiler that's like boiling super hard water for years on end.

And it's already completely covered in calc. You know, those images of the Titanic when it's like lying on the bottom of the sea?

Lucia Solis:

I am a child of the 90s. I was a young girl. Of course, I'm very familiar.

James Harper:

So remember those scenes where the submarine goes down to like the bottom of the sea to see the Titanic today? And we see like the metal railings all like gunked up and slimy and like this thick layer of corrosion. These boilers look like that.

And in fact, what's that thing that flopped? Something has flopped off. There was this like piece.

Wow. What I would call a limescale like snake.

Samo Smrke:

Limescale.

James Harper:

So literally, it's like a snake.

Samo Smrke:

Yeah.

James Harper:

Like the limescale is so solid. It's literally turned into a snake that's just like detached itself and swimming around in the water. Yeah.

This is crazy.

Lucia Solis:

Ew. That sounds really gross. But is that limescale, I mean, that's being bound in like in the machine.

So it's not actually getting into my coffee. So is it harmful for us? Is it harmful for us to digest it?

James Harper:

No, the good news is it's not harmful. It is really bad for your machines in that it'll make your boilers much less efficient, which is bad for the environment. Of course, you need more energy to like heat up the water.

It's expensive to fix, but it's not going to kill you.

Lucia Solis:

So we don't have to panic.

James Harper:

No need to panic.

Lucia Solis:

But what can we do about it?

James Harper:

So like I explained earlier, limescale is formed when you have calcium and hydrogen carbonate reacting together at high temperatures. So to stop them from coming together in the first place is to never boil water. Always drink cold coffee.

Lucia Solis:

Ah, well, I can do that. I live in a hot place. That's fine.

Everybody, okay, wait, wait. Solution one is first move to a hot location so that you can only drink cold coffee.

James Harper:

That's right. Yes.

Lucia Solis:

Gotcha. So we need to change our preferences and make sure we stop liking hot coffee.

James Harper:

That's the easiest solution.

Lucia Solis:

Good advice. All right.

James Harper:

But if you're going to be a stick in the mud and keep drinking hot coffee, then solution number two, reduce the total hardness of your water. And you do that by reducing the amount of calcium and hydrogen carbonate in your water.

Lucia Solis:

So you're saying zero calcium and hydrogen carbonate in the water?

James Harper:

No, not zero, because water that is incredibly soft, you know, where it has very little dissolved in it, it is actually corrosive. It could corrode the metal boiler in your espresso machine. It'll corrode the parts, the pipes moving the water around.

Lucia Solis:

I don't personally have that problem because I'm not making espressos at home. But if I were, I'm really glad that I know that this is an issue. And actually, I've already told friends that have espresso machines who are using like distilled water, that they're about to ruin their machine.

James Harper:

No, you use distilled water in espresso machines?

Lucia Solis:

Yeah.

James Harper:

That's going to corrode them.

Lucia Solis:

That's what they thought they were supposed to do. He's like, I thought I was supposed to use distilled water. He knew that he had to do something special.

So yes, we've already saved one person in Ohio from ruining their espresso machine.

James Harper:

That's wild.

Lucia Solis:

They were using distilled water.

James Harper:

This is going to be a check for like $1,000. I mean, you've really saved them a lot of money. So what your friends need actually is like the thinnest of thin limescale linings in their espresso machine boiler.

Lucia Solis:

Okay, so I don't want too much because that's a problem. And if I have none, that's a problem too.

James Harper:

Exactly. Again, it's like that Goldilocks thing. You don't want water which has too much calcium and hydrogen carbonate because that'll come out as limescale.

You don't want zero because a little bit of limescale can actually protect the metal from being corroded. You want that sweet spot in the middle. You want water that's just a little bit hard.

Lucia Solis:

Okay, James. So where I'm at now is I understand that I want some alkalinity in my water because if I have zero, then my coffee is totally out of balance and too acidic and harsh. And I've also learned on the other end that with limescale, that there is a protective element to it.

I also want a little bit of that to protect the equipment, but not so much that it causes a problem.

James Harper:

Exactly.

Lucia Solis:

But the thing that I'm still struggling with, James, is that these words are too vague for me. Everybody's little bit is different. So how much is too much?

How much is too little?

James Harper:

Don't worry, Lucia. In the next episode, I'm going to take you into how you can measure the hardness and alkalinity of the tap water and then what you can do to get great water for coffee.

Lucia Solis:

Sounds good.