What's a good ppm alkalinity level for coffee brewing water?

[Silver_Is_Money]

For 1.3 grams of baking soda added to 4 gallons of RO the pH computes to:

MW of NaHCO3 = 84.0066 g/mol

1.3 g/84.0066 g/mol = 0.015475 moles of NaHCO3

4 gallons = 15.1416 Liters

0.015475 moles / 15.1416 Liters = 0.001022 molar HCO3- concentration

Log(0.001022) = -2.9905

pKa = 10.329

pH = 10.329 + -2.9905 = 7.34

Edited to correct the molecular weight of baking soda.

 

[Silver_Is_Money]

I made a batch of coffee using water from our under the sink RO unit and a batch with the same RO water plus baking soda adding ~51 ppm of additional alkalinity. No other minerals added. Drinking them side by side at the same temperature I'm noticing little to no discernible flavor differences between them sans for slightly less acid bite for the batch that received the baking soda. If anything, acid reduction alone (plus some added sodium) is actually making the baking soda coffee ever so slightly less flavorful and more dull tasting than the straight RO coffee. This was highly unexpected. To my pallet none of the rich chocolate like flavors I received from the baking soda plus other minerals coffee are derived from the addition of baking soda alone.

The difference in make-up was 2.2 Liters of RO plus 0.19 grams of added baking soda vs. 2.2 Liters of RO only.

 

[Silver_Is_Money]

In all honesty I'm barely discerning the acidity difference, and if this had been done as a blind taste test I may well have failed to pick the odd coffee out.

 

[Robert65]

Well, it seems you're approaching a general truth, that "natural" waters make better coffee than deionized water. Which is more or less conventional wisdom, WRT coffee, tea, baking, and cooking in general. A moderate level of many minerals will probably be beneficial, but specifics may not be terribly critical, as long as the water itself is palatable -- which some well water isn't. (In fact deionized water doesn't even make good tasting drinking water, IMO.) My hypothesis.

 

[Silver_Is_Money]

OK, this might be better (???):

pH = pKa + log(molar concentration)

pKa1 for Ca(OH)2 = 11.57

log(0.00102) = -2.99

pH = 11.57 + -2.99 = 8.58 (which is nowhere near as scary as pH 11.01)

But then there is also pKa2 = 12.63... Hmmmm????

I'm still thinking about this pH determination matter (where is AJ when I need him?).

pKa1 (11.57) is strictly associated with the release of the first of two OH- ions from the Ca(OH)2, and pKa2 (12.63) is strictly associated with the release of the second of the two OH- ions. Therefore if the molar concentration of OH- is 0.00102 for the case of both ions being liberated, it is half of that for each individual OH- ion, or 0.00102/2 = 0.00051 molar.

For the first OH- ion release we get:
log(0.00051) = -3.292
pH = 11.57 + -3.292 = 8.278 pH

For the second OH- ion release we get:
log(0.00051) = -3.292
pH = 12.63 + -3.292 = 9.338 pH

The upper limit for the pH is 9.34, and the lower limit for the pH is 8.28, and the reality is likely to fall somewhere between these two extremes (presuming of course that this general method is even related to the correct method to begin with, which it may well not be). Their average comes to 8.81 pH, but somehow I doubt that averaging is how the correct answer is to be calculated. Calling @ajdelange for assistance here. And also welcoming anyone else who can show how this pH is properly to be calculated.

 

[Silver_Is_Money]

Of course I could just go out and get 4 gallons of Clearwater Systems RO water and add 0.57 grams of pickling lime to it, stir well, and then take the pH reading of it with my new (and still not yet out of the box) pH meter. That might tell me something.

I can't use my under the sink RO unit for such precision science, because my RO's TDS is well above the typical TDS of Clearwater Systems RO.

 

[mabrungard]

Well, it seems you're approaching a general truth, that "natural" waters make better coffee than deionized water.

That’s a generalization that only a few water sources can claim. Many sources have too much alkalinity and that’s a detriment to many beverages.

 

[Robert65]

That’s a generalization that only a few water sources can claim. Many sources have too much alkalinity and that’s a detriment to many beverages.

By natural I just meant mineralized, that some minerals are necessary, as opposed to deionized. That probably also applies to most beverages. I should have worded it differently.

 

[Silver_Is_Money]

New morning, new test. This time I've mineralized 4 gallons of our under the sink RO with 1 gram each of CaCl2, CaSO4, MgSO4, and baking soda. By cutting the baking soda from 1.3 grams to 1.0 grams I'm attempting to compensate for the alkalinity present within our homes mediocre RO water vs. high quality Clearwater Systems RO water.

I'm presently sipping on coffee brewed with straight RO water from my under-sink RO unit, while also sipping on coffee made from the above described mineralized RO water. The brews were made as equally otherwise as I could make them.

The bottom line is that the mineralized under-sink RO water coffee has most (but not quite all) of the delicious rich chocolate character that I remember from the earlier premium quality Clearwater RO with minerals coffee, and the straight RO batch tastes flat, dull, and empty by comparison. It basically tastes "watery" or "weak", as if it needs perhaps 20% to 25% (as a first guess) more beans. But I know that I weighed both 12 cup coffee pots beans out to be the same to within a fraction of a gram.

The only difference I note is that since our home RO unit starts out with what I'm presuming to be ~20 ppm alkalinity, I'm not detecting any of the acrid acidity of the straight Clearwater RO based coffee, the source for which which has almost zero alkalinity. Apparently around 20 ppm alkalinity is totally sufficient to alleviate the acidity issue. But with no chocolate qualities, and also no acrid/acid qualities, the home RO unit sourced coffee has literally no character going for it and thereby "hopelessly weak" is all that can be said for it. It is the worst coffee of all. And it is also what my wife and I normally drink.

I'm now thinking that I didn't go quite far enough in cutting the added alkalinity of my under-sink RO water, and that for this water about 1/2 to 3/4 gram of baking soda added to 4 gallons of our RO should be plenty. It may even be that it doesn't need baking soda to boost its alkalinity at all, since I'm not detecting acidity in the coffee made from it.

I should state that our under-sink RO unit is being fed from 377 ppm alkalinity (softened) well water, and that is why I initially presume that it has somewhere around 20 ppm (or more, could it be 25-30 or higher ppm?) of alkalinity.

 

[aeviaanah]

New morning, new test. This time I've mineralized 4 gallons of our under the sink RO with 1 gram each of CaCl2, CaSO4, MgSO4, and baking soda. By cutting the baking soda from 1.3 grams to 1.0 grams I'm attempting to compensate for the alkalinity present within our homes mediocre RO water vs. high quality Clearwater Systems RO water.

I'm presently sipping on coffee brewed with straight RO water from my under-sink RO unit, while also sipping on coffee made from the above described mineralized RO water. The brews were made as equally otherwise as I could make them.

The bottom line is that the mineralized under-sink RO water coffee has most (but not quite all) of the delicious rich chocolate character that I remember from the earlier premium quality Clearwater RO with minerals coffee, and the straight RO batch tastes flat, dull, and empty by comparison. It basically tastes "watery" or "weak", as if it needs perhaps 20% to 25% (as a first guess) more beans. But I know that I weighed both 12 cup coffee pots beans out to be the same to within a fraction of a gram.

The only difference I note is that since our home RO unit starts out with what I'm presuming to be ~20 ppm alkalinity, I'm not detecting any of the acrid acidity of the straight Clearwater RO based coffee, the source for which which has almost zero alkalinity. Apparently around 20 ppm alkalinity is totally sufficient to alleviate the acidity issue. But with no chocolate qualities, and also no acrid/acid qualities, the home RO unit sourced coffee has literally no character going for it and thereby "hopelessly weak" is all that can be said for it. It is the worst coffee of all. And it is also what my wife and I normally drink.

I'm now thinking that I didn't go quite far enough in cutting the added alkalinity of my under-sink RO water, and that for this water about 1/2 to 3/4 gram of baking soda added to 4 gallons of our RO should be plenty. It may even be that it doesn't need baking soda to boost its alkalinity at all, since I'm not detecting acidity in the coffee made from it.

I should state that our under-sink RO unit is being fed from 377 ppm alkalinity (softened) well water, and that is why I initially presume that it has somewhere around 20 ppm (or more, could it be 25-30 or higher ppm?) of alkalinity.

Can you post grams per gallon of minerals for treated water? I’d like to check if I get similar results. I get 4ppm out of my RO

 

[Silver_Is_Money]

Can you post grams per gallon of minerals for treated water? I’d like to check if I get similar results. I get 4ppm out of my RO

Mineral quantities are listed within the post you quoted.

 

[Silver_Is_Money]

I'm back to 11 being the correct pH for 4 gallons of RO water with 0.57 grams of added calcium hydroxide. Please ignore any of my posts to the contrary within this thread. And 1.3 grams of Baking Soda added to 4 gallons of RO water results in a pH of 8.27. See this online calculator for verification with respect to both minerals: http://www.aqion.onl/reacs/new/232404

Despite the vast disparity in these two minerals resulting water pH's, their alkalinities are equivalent.

 

[bierhaus15]

I've futzed around with coffee water chem for a few years now and have my water dialed in for the coffees I prefer; lightly roasted and high acidity Africans, lactics, and S. American stuff like Geshas. Kalita and V60 pourovers. I also make a pretty good espresso on my Flair, but it can be inconsistent. That said, I generally try to keep alkalinity below 60 and limit the amount of sodium and chlorides in my water. Generally, higher ALK can be overcome by increased Ca/Mg extraction and S04. Some general findings:

Ca - heavier, creamier mouthfeel, can be dry/earthy in high amounts
Mg - crisp, smooth, highlights fruitier character
Na - bitter, flat character > 20 ppm
Cl - sharp, dull, bitter above 30 ppm
S04 - crisp, bright, dry, fruity

The principle ions for coffee extraction are Ca and Mg, although too much of either are not ideal. Sweet spot for calcium hardness for my process is around 45, and I prefer more Mg/S04 to accentuate sweet-high acidity flavors; berry, tropical fruit, ect. For darker roasts and French-Italian style espresso, I've found the opposite to be ideal; higher Ca, Cl, Bicarb for improved body and reduced acidity.

My general profile for balanced, medium-acidity coffee with good mouthfeel is:

Ca-19, Mg-29, Na-11, S04-113, Cl-16, Bicarb-58, ALK-45

All said, water does amazing things for coffee, but it won't make badly brewed or roasted coffee that much better... and grind consistency is still key.

 

[Buckeye_Hydro]

Our commercial coffee customers typically shoot for about 50 ppm TDS for coffee brewing water. An inline calcite filter is sometimes used as well.

 

[mabrungard]

Russ, what are they adding typically to achieve that TDS? There are many ways to raise TDS.

 

[Buckeye_Hydro]

What I see most often is use of a blending valve that mixes permeate with de-chlorinated feedwater. Can be custom blended to a desired end TDS with use of an inline TDS meter.

 

[The_Bishop]

New morning, new test. This time I've mineralized 4 gallons of our under the sink RO with 1 gram each of CaCl2, CaSO4, MgSO4, and baking soda. By cutting the baking soda from 1.3 grams to 1.0 grams I'm attempting to compensate for the alkalinity present within our homes mediocre RO water vs. high quality Clearwater Systems RO water.

I'd like to thank you for posting this. I've been screwing around with building water for coffee for a while, and getting somewhat frustrated. I was dosing my RO water (4 TDS) very simply with CaCl and Sodium Bicarb, as I figured that the chloride would give the coffee that full/round flavor. However, the mix noted here has really transformed the cup. Been brewing a cup at a time with an aeropress inverted. One of these days I need to upgrade my grinder, but I'm having a hard time justifying the cost when my capresso infinity has been working so well.

 

[The_Bishop]

In the spirit of further experimentation, I decided to come up with a slightly different profile.

In one gallon of RO water with a 4 TDS reading:
.25g Gypsum
.20g Calcium Chloride
.25g Magnesium Chloride
.3g Baking Soda

Ends up with a water profile of:
Calcium:34 Magnesium:8 Sodium:11 Sulfate:37 Chloride:57 Alkalinity:55

I'm hoping the lowered sulfate and added chloride will take a hint of the 'sharpness' out of the coffee, possibly enhance the 'chocolate' aspect of it.

I've also retired my capresso infinity grinder. It's shot, makes tons of fines. Never realized how bad until I actually examined some of the ground coffee up close. I have a hario hand grinder I used very briefly before I bought the capresso, it's now back in service until my baratza virtuoso shows up. The hand grinder, set for the same grind size as the capresso, is far more consistent and has far less fines. While I'm happy about the better coffee I am far less enthusiastic about the hand grinding part of the caffeine ritual now.

 

[Silver_Is_Money]

In the spirit of further experimentation, I decided to come up with a slightly different profile.

In one gallon of RO water with a 4 TDS reading:
.25g Gypsum
.20g Calcium Chloride
.25g Magnesium Chloride
.3g Baking Soda

Ends up with a water profile of:
Calcium:34 Magnesium:8 Sodium:11 Sulfate:37 Chloride:57 Alkalinity:55

Let us know how it turns out with this profile.

 

[The_Bishop]

Sitting here sipping this as I type.

The coffee definitely has a softer mouthfeel. Chocolate notes are more prominent, but in balance with the fruitiness. The sharpness I thought might be contributed by the higher sulfates is definitely softer. Overall it's pretty good but I will probably cut back the baking soda on the next gallon. It might be because I'm so used to a more acidic bite to the cup, but it seems almost a little too smooth.

 

[Silver_Is_Money]

I think the next 5 gallons of RO that I modify for coffee use will get the following addition:

2.8 grams of CaCl2.2H2O (I.E., the dihydrate state of CaCl2*)
1.5 grams of Epsom Salt
1.4 grams of Baking Soda

*Note: For fresher CaCl2 at a presumed 95% purity level, this would become ~2.2 grams of CaCl2

 

[The_Bishop]

That should be interesting, let me know how it compares taste wise with the higher concentration of chloride.

 

[mabrungard]

I recently used a formulation of half gram of gypsum, calcium chloride, epsom, and baking soda per gallon. Essentially double the dosage suggested by Larry and it was pleasant. I’m getting the impression that coffee water content is forgiving. But I do feel that having sufficient alkalinity is probably important.

 

[The_Bishop]

Wow, that's a bit of an eye opener. Would think with the sulfates in the 125 range it would be very dry.

Might be worth talking about how the coffee is being made. I've been brewing inverted aeropress with a relatively fine grind, so full immersion.

 

[The_Bishop]

My Baratza grinder finally showed up.

My god, what an eye opener. What a difference a grinder makes. No fines, very consistent grind. Same coffee, same grind size, same weight of coffee, same water. Only difference is the grinder. Cup is 50% better.

 

[The_Bishop]

I think the next 5 gallons of RO that I modify for coffee use will get the following addition:

2.8 grams of CaCl2.2H2O (I.E., the dihydrate state of CaCl2*)
1.5 grams of Epsom Salt
1.4 grams of Baking Soda

*Note: For fresher CaCl2 at a presumed 95% purity level, this would become ~2.2 grams of CaCl2

Did you ever try this out, and how was it?

 

[Silver_Is_Money]

Did you ever try this out, and how was it?

I haven't tried it out yet. My wife likes coffee made from our RO water. But then I must note that our RO water (starting from a well with 720 ppm Total Hardness, and 377 ppm Total Alkalinity as CaCO3 per Ward Labs) weighs in at about 35 ppm alkalinity.

 

[The_Bishop]

Hmm. Maybe next time I run out of water for coffee I'll give it a shot.