I've begun formulating water for espresso by preparing saturated calcium bicarbonate using reverse osmosis water, a Soda Stream carbonator and food grade calcium carbonate powder.

Calcium carbonate is nearly insoluble in water. Simply adding it to water will not produce anything but slight calcification and a layer of undissolved material on the bottom of the water container.

Calcium bicarbonate exists only in aqueous solution. It is formed in nature when rainwater reacts with the carbon dioxide to form carbonic acid, which falls on the earth and comes into contact with rocks and soils containing calcium carbonate. The reaction of carbonic acid and calcium carbonate produces dissolved calcium in the form of calcium bicarbonate. This form of bicarbonate is the basis of temporary hardness. Increasing the temperature of the water drives off the bicarbonates, which precipitates as calcium carbonate scale on the inside of boilers, pipes and water heaters and so on.

A certain amount of mineralization, particularly in the form of calcium content, is favorable in the brewing of coffee and espresso. However, too much of it contributes to scaling and clogging of equipment.

Other minerals influence both coffee quality and machine life. LaMarzocco publishes a water specification for use with their machines to provide both optimal machine life and quality coffee.

In my own particular case, my city-supplied water is very hard. It also contains a high level of chlorides, which render it unsuitable even when diluted with distilled or reverse osmosis water. My home is equipped with a water softener and a small, under-sink RO system to provide purified and demineralized water. But no degree of blending results in suitable espresso water.

A simple solution is to produce a concentrated calcium bicarbonate water solution and use that for blending with RO water to achieve the desired amount of calcium hardness in water.

The production of calcium bicarbonate is easily achieved by introducing calcium carbonate powder into carbonated water. Carbonated water is readily purchased in grocery stores, but can also be prepared at home with a simple apparatus like the SodaStream Fizzi carbonator. The SodaStream is commercially available for about $70. It comes with a CO2 gas cartridge good for about 60L of water and a 1-L bottle for carbonating water.

Preparation is very simple:

1. Fill the SodaStream bottle with 1-L RO water from the home system.
2. Introduce 1.0g of food grade calcium carbonate into the bottle and shake to distribute.
3. Insert the bottle into the SodaStream device and press the carbonation button, following the manufacturer's instructions.
4. Cap and place the carbonated solution into the refrigerator overnight.

The result is a slightly cloudy water solution with a small amount of calcium carbonate powder present on the bottom of the bottle. Most of the powder is consumed in the reaction is now dissolved in the form of calcium bicarbonate in the water.

Measuring the solution at room temperature indicated about 700ppm using a simple pocket TDS meter.

The concentrate is then blended into a larger volume of RO water at about a 1:10 to 1:20 ratio and adjusted to arrive at the desired 50-70ppm (3-4 GPG) of calcium hardness.

EDIT: I have found that the strength of the concentrate can vary considerably. It is best to use a TDS Meter to titrate the mixed water to the desired hardness level. Adjust the temperature of the purified water (RO or distilled) to about 25c (77f) and measure it with a pocket type TDS meter. Add a small amount of concentrate solution, stir or agitate to mix thoroughly, take a reading. I'm targeting about 65ppm at standard temperature with the meter.

Confirmation of general and carbonate hardness and pH were made with API aquarium test kits and found to be in the desired ranges.

Costs:

$0.019 per gram Food grade calcium carbonate powder.
$0.25 per liter operating cost of the Soda Stream( based on 60L exchange CO2 tank cost of $15. )
$0.27 per liter cost of concentrate solution (cost of RO water not considered)

$0.0027 per liter of brewing water at a 1:10 blending ratio (cost of RO water not considered)

Apparatus costs:
$79 SodaStream
$129 undersink RO system ( big-box home improvement store, ranges from $129-$150 for similar systems).
$105 annually for RO filters and membrane cartridges. (note that the RO system is used for household purposes, not exclusively)

As the RO system use is simply part of the normal household water usage in my home, it is difficult to calculate the costs. With a daily capacity of 18 gallons and 6 month filter and 2yr membrane schedules one could suppose it 6500 gallons at about $0.016 per gallon. I don't think I use the full capacity at all and the filters are on a schedule vs. volume replacement. Figure it $0.02 per liter of finished RO water.

Makes my water cost about $0.023 per liter, (less than 9 cents per gallon) not counting amortization of apparatus and labor to maintain the system and do the blending.

Bravo Larry, impressive to see some out of the box thinking for espresso water.

I'm in a very similar water situation in soCal and will give your method a shot as I have all the tools minus the calcium which I'll soon pick up.

Thanks for making the effort.

Very cool solution for getting rid of everything except what's needed to make great coffee.

I take it you use the Mini's reservoir or a Flo-Jet system?

Funny timing of this as I've been wracking my brain hard this past week to try and determine what I would be doing.

Problem ::

We're on a salt-based softening system for our well water. We're about to buy an expensive RO system. I would ideally like to plumb in my machine via the RO line, but I'm obviously running into the same problem you are. I was thinking of adding the BWT Bestmin cartridge after the RO, but at $275 CDN + $110 adaptor, it's an expensive experiment. We would also like to remineralize for drinking water, so I think this might be my only solution.

If I end up using my machine via tank I will definitely be revisiting this solution! Thanks for the detailed write up!

I'm using the machine's tank. I'd love to plumb in, but so far, haven't figured out how to supply the machine with really suitable water.

It's really simple and after doing some internet searches, some other people have arrived at the same method to prepare water. I'm not sure what other minerals, if any, are desirable. Homebrewers have been into water chemistry for a long time and have some interesting ideas on water.

Nice post, Larry!

I've been doing much the same, and was using my Cuisinart CO2 spritzer (it was a gift) that I can no longer get cartridges for. Now I'm just skipping the CO2 spritz of my concentrate, and at my concentration It still seems to work as long as I give the concentrate a vigorous shake before adding it to my big jug.


FWIW:
My current recipe is lower in hardness than yours but has good alkalinity. I shoot for a final concentration of each salt, CaCO3, MgCO3, and KHCO3, at ~ 0.2 mmole/L. That gives me a calcium hardness of 20 mg/L, total hardness of 40 mg/L, and total alkalinity of 50 mg/L (in CaCO3 equivalent.) Even without CO2, that dilution is not cloudy and leaves no sediment at the bottom of my big jug. I make up a 67x concentrate and add one 45 ml shot of it to my 3 liter jug of pure water.

I love my soda stream. I have a 20lb CO2 tank connected to it. I haven't had to refill for more than a year at this point. It makes it insanely affordable. Your idea is really remarkable. I don't think I have your same needs, but I wonder what else having a carbonator opens things up for experimentation.

Interesting. The description of a very similar method can be found at http://grindscience.com/2015/08/making- ... pe-so-far/

napierzaza wrote:I love my soda stream. I have a 20lb CO2 tank connected to it. I haven't had to refill for more than a year at this point. It makes it insanely affordable. Your idea is really remarkable. I don't think I have your same needs, but I wonder what else having a carbonator opens things up for experimentation.

Poor man's whirlpool bubble baths

Besides, I like a nice cold sparkling water after an espresso.