# Perfect Espresso Water Chemistry

## Summary:

Trying to formulate the perfect water for espresso brewing.

## Main Question or Discussion Point

Hey all,

I've come here to seek out some help creating the perfect espresso brewing water. I've done some research, and I think I've reduced it down to a chemistry problem. I'll be starting with distilled water and adding minerals, some 'hardness' and an 'alkalinity buffer.'

First, here's the target:
https://scanews.coffee/2013/07/08/dissecting-scaas-water-quality-standard/

target summary:
150 mg/L of total dissolved solids
approximately 50-70 mg/L of hardness, they mention calcium here but that causes scale build up in espresso machine. Magnesium sulfate seems to be a good substitute
40 mg/L alkalinity
pH of 7
10 mg/L of sodium

This video has served as a good 'baseline' for me to start at:

I immediately notice that this is water has 237 mg/L of TDS, and it has a little too much sodium:
(.185 L of alk buffer added to gallon) * (1400 mg/L concentration of alk buffer) * (.27 percent sodium by mass of NaHCO3) * (1 Gal / 3.78 L) = 18.5 mg sodium

A couple things I've learned while researching:
Sodium bicarbonate breaks down around 50C/122F, whereas potassium bicarbonate does not break down until 212F. Espresso brewing temperature is between 195F - 205F. The boiler stays 200F for long periods of time. I've read online, from not *necessarily* credible sources, that as sodium bicarbonate breaks down it can cause damage to the boiler of the espresso machine.

Magnesium sulfate might be better for the hardness of the water, as calcium leads to more scale build up in the espresso machine.

My thought is that I can use a dominantly potassium bicarbonate alkalinity buffer with a touch of sodium bicarbonate (maybe for 5 mg/L - 10 mg/L concentration), and I can use magnesium sulfate for hardness. My concern now though is to have the total dissolved solids equal 150 mg/L and keep the pH at 7 (and while worrying about 40 mg/L alkalinity? though perhaps this is intrinsic to keeping the pH at 7).

It's been literally 10 years since I've taken Chemistry. I vaguely recall that I'll need a balanced chemical equation and to do some conversions between molar mass and mass; however, I wouldn't really know where to start with the balanced equation..

NaHCO3 + KHCO3 + MgSO4 + H2O --> ?

And I'm not sure how to find the resulting hydrogen and hydroxide ion concentrations in order to balance pH.

Any help is much appreciated!

Borek
Mentor
This is not just about a single reaction equation.

I would start by deciding on substances which I would use. Then I would describe the system with several mass balances to control TDS an sodium, throw in equations describing the acid/base equilibrium of the system - and finally I would start playing with numbers. Some thing would be known immediately, others would require refining.

(note: water hardness is often reported in mg CaO, that doesn't necessarily directly translate into mg of magnesium)

WWGD
Gold Member
2019 Award
A general comment for Curious: Have you heard of gastro pubs? A relatively-recent trend on using chemistry in cooking in order to optimize flavor, general effect on food.

Which substances I want to use:
Sodium Bicarbonate, NaHCO3
Potassium Bicarbonate, KHCO3
Magnesium Sulfate, MgSO4 + 7H2O (just learned that epsom salt is heptahydrate)
Distilled Water, H2O

Not a single reaction equation... I'm not sure which reactions might occur, but my guess might be...
NaHCO3 + KHCO3 + H2O ---> Na(+) + OH(-) + K(+) + H2CO3 ---> Na(+) + OH(-) + K(+) + H2O + CO2(aq) ---> Na(+) + OH(-) + K(+) + H2O + CO2(g)

and

MgSO4 + H2O ---> Mg(+) + SO4(-) + H2O

and once I understand the products of those equations, I can write an equation on how they react together?
Na(+) + K(+) + Mg(+) + SO4(-) + OH(-) + H2O ---> NaSO4 + KSO4 + MgOH + H2O

Kinda guessing here based on my rusty knowledge of ions, dissociation and googling.

"Then I would describe the system with several mass balances to control TDS an sodium, throw in equations describing the acid/base equilibrium of the system"

I'm not sure that I understand you entirely, but may you mean a set of simple equations?
let x = mass of sodium bicarbonate
let y = mass of potassium bicarbonate
let z = mass of magnesium sulfate

x + y + z = 150
x * (.27) = 5 (anywhere from 5 to 10)

And maybe there's a way to associate these masses (maybe converted to moles) into the equations which inevitably need balancing, but I'm not sure how.

For equations decsribing acids and bases, I'm familiar with pH=-log([H+]) and pOH=-log([OH-]).. I'm not sure how to determine those by the end products (assuming my end products are even correct).

Right, I wasn't aware hardness was only for CaO. Regardless, Magnesium Sulfate seems like a good alternative.

@WWGD, I've heard of Gastro Pubs but I haven't heard that they use chemistry to enhance flavors. Interesting though. Guess I'll have to try one

WWGD
Gold Member
2019 Award
Sorry, I misspoke, it is not true for gastropubs in general; I really meant to refer to the general area called molecular gastronomy which deals with this.

Last edited:
jim mcnamara
Mentor
Beer companies routinely have this problem - to maintain constant results requires that water and all of the ingredients (barley, wheat, water, IBU of hops, whatever) are very closely monitored.

There is some equipment and software that very small companies can get to deal with the problem. Especially when the water source is the community system.

LaMotte (Brew Lab), Ward Laboratories are two companies that make water test kits. See if they meet your needs. <these two sites are not completely secure so our URL generating software biffs the link, sorry>

http://www.wardlab.com This link may not work correctly, so type $www.wardlabs.com$ lose the # # # # things

Lamotte sells kits for the entire beverage industry and home use, too. Same problem with our URL generating software here:
www.lamotte.com## may NOT be a valid link -- you type this as it appears.

Ugggh - this looks like a ransom note....

Tom.G
Don't know how potent it is, but Magnesium Sulfate is a laxative.
Be careful with the testing!

jim mcnamara
Mentor
IMO, the OP is using a backdoor approach. Beverage workers first choice is chemical additives that already exist in water. Distillation is an added cost. I'm told by the owner of a local brewpub.

Plus, subjective tasting also involves plant polyphenols and complex terpenes and metal complexes which are present in surficial groundwater - water in the top 150m or so of the water table. (Article link below)

Well water from different geographic sources/geologic formations tastes different for a variety of reasons, I'm sort of "shortcutting" the subject to keep it manageable. This varying taste thing is major bugaboo for companies like Coca-cola because it is difficult to maintain consistent taste with bottling plants all over a given country.

An example is Arsenic in groundwater, for which there are defined limits:
https://www.usgs.gov/mission-areas/water-resources/science/arsenic-and-drinking-water?qt-science_center_objects=0#qt-science_center_objects

Also using inexpensive distilled water from grocery stores may not be what you intend. The stuff meant for steam ironing clothing is certainly not usable in the lab for many kinds of analyses (Type I .... Type IV).

Ex: https://www.labconco.com/articles/water-type-difference