Hey,

Currently, I'm mixing my water to 66ppm nahco3 (39ppm alkalinity) and 75ppm mgso4 (62ppm hardness).

I was thinking about using calcium chloride instead of half the magnesium sulfate so I'd get half the hardness from one and half from the other.

How would that affect flavour and extraction?

For pourover I think you can give it a try and see if it tastes better or worse. Not for espresso though - in an espresso machine you don't want that chloride for corrosion reasons.

There is a conventional wisdom that magnesium is preferential to calcium for extraction. I think a lot of that is based on this paper: The Role of Dissolved Cations in Coffee Extraction . That paper has to do with calculations of binding energies and not measurements of actual coffee extractions. Comparisons of refrectometer measures have not found a difference between Mg vs Ca in the brewing water.

There is one taste test experiment, sponsored by BWT, and done by the folks at the Zurich University of Applied Sciences associated with the SCAE. Ive not seen the paper*, but a discussion is in the Winter 2016 Cafe Europa - can be found here - https://www.bwt.com/en/-/media/bwt/glob ... _22-26.pdf.
In that experiment, they purportedly found significantly higher astringency and bitterness scores when the proportion of calcium to magnesium was high. Of course this was a cupping study of only one coffee (washed El Salvador Pacamera with a light roast) so you can't assume it's generally true for other coffees.

Here's a teaser snapshot from that 2016 Café Europa article:

From Charting Water for Better Coffee, Café Europa, Winter 2016


* If you have SCA membership, you might look for an actual research paper here: https://sca.coffee/available-research-members
Edit addition: Alas, you won't find that study there, even with members only status. This study apparently never was written up and published as a scientific paper.

Edited update - The magazine article is no longer available at https://www.watertops.de/global/downloa ... _22-26.pdf, so I corrected the link in the text above to a reprint pdf hosted by a BWT.

I have tried doing what you are thinking about in past. For some reason the calcium chloride stock got cloudy and funky smelling. I didnt really trust it much after that. I have not found the same issue with mag stocks....

I bought some CaCl2 and gave it a go. It wasn't as sweet and tasted a bit funky.

I think I'm gonna stick to Mg.

The problem for me with epsom salt is that sulphate in higher concentrations dosen't do anything good for the coffee, in fact it tend to result in a very disgusting after taste, so I always keep it relatively low.

I'll question the reliability of that paper, first it's sponsored/funded by a filter manufacturer who make ionexchangers who exchange Cl ions with Mg. secondly testing one coffee simply isn't enough to conclude anything. I have done multiple cupping and I just can't recognise the picture, I have found allot of coffee brewed with mg heavy water rather astringent more so then Cl water, while the latter being more acidic.

Would you care to further define "heavy"? What kind of PPM were you testing with mag vs. cal.

malling wrote:I'll question the reliability of that paper, first it's sponsored/funded by a filter manufacturer who make ionexchangers who exchange Cl ions with Mg. secondly testing one coffee simply isn't enough to conclude anything.

It is true that BWT sponsored the study, and they do push the "flavor enhancing magnesium" angle with their patented filter that replaces some Ca ions with Mg. But I don't think that's a good reason to completely discount the study, especially since I've not seen it. The Cafe Europa article is like many articles in the coffee press, which often oversimplifies or overstates a scientific study's results. I think the scientists at ZHAW are competent and would not bias a study towards a sponsor, so would withhold any judgement about that until I saw the study. My guess is that their conclusions would make the same point as yours - that this is just one taste test of one coffee. Also I'd like to see the data, as in how many tasters and the statistical significance of those scores.

To me, it is interesting to see that there was one case where tasters appeared to see a difference between Ca vs Mg ions in the brew water. I have always discounted that as very unlikely, based mostly on the fact that the Ca and Mg ions in the incoming water are a small fraction of the amount of Ca and Mg in the soup flowing through the puck that were dissolved from the coffee itself.

Edit addition: Except for that magazine article, as of Oct 2019 I've still seen no publication of that study. I tried finding it on the SCA site with member status to no avail, and don't even see it on Professor Yeretzian's list of projects, papers, and presentations at ZHAW (https://www.zhaw.ch/en/about-us/person/yere/) So I'm now more inclined to discount it as valid support for the 'flavor enhancing magnesium' hypothesis.

RyanJE wrote:Would you care to further define "heavy"? What kind of PPM were you testing with mag vs. cal.

I think it was 130-160ppm of CaCo3 equivalent.

http://grindscience.com/2015/04/making- ... additions/

I calculated "the formula" from the chart here. I'm not a chemist though...