Pressino wrote:Coffee itself contains minerals (including Ca and Mg...) so I would tend to think it won't make much difference if you DON'T add any extra calcium to the brew water, and it certainly would be a good idea to leave it out if your goal is to minimize scale in your machine. Just my opinion but more knowledgeable folks may want to correct me if I'm wrong.

alfredocalza wrote: Do you use Calcium instead? Isn't that bad for your machine? For what I have tasted, I feel like distilled water alone is more acidic. Mineral water (which probably contains lots of Calcium, is not acidic at all. The water that I make with magnesium sulfate and potassium bicarbonate is not as acidic as the distilled water, but still a little acidic. It also has a very slight bitter taste at the end, which I suppose should be because of the magnesium. Do you have a water recipie for espresso that I could try in order to get better results?

homeburrero wrote:Are you using magnesium sulfate or are you using Epsom salt? They both contain MgSO4, but Epsom is a hydrate that has a lot of water. If we assume you are using Epsom salt, then your recipe comes out to a total hardness around 58 mg/L and an alkalinity around 63 mg/L (in CaCO3 equivalents). Since the hardness is all magnesium it will not cause limescale. The alkalinity is more than sufficient for corrosion protection. It's within typical recommendations for hardness / alkalinity (see the chart here: Good references on water treatment for coffee/espresso .)

But I think you may have cloudy precipitation if you are mixing both the Epsom and the bicarbonate in one concentrate bottle. You can shake it really well before using. Or if you keep your two concentrates in separate different bottles it won't precipitate.


Chloride ion, like you get with calcium chloride, CaCl2, is corrosive, especially to brass and copper. You sometimes see CaCl2 recommended as a way to add some soluble calcium to your water, and you can do that for pourover, but it would not be good for use in an espresso machine.

Sulfate ion, like you get with magnesium sulfate, MgSO4, is far less corrosive. You often see Epsom salt in these recipes as a handy source of MgSO4. Epsom salt is readily available, dissolves nicely if you shake and stir a while, and should not create a scale problem at reasonable concentrations. A recipe with both sulfate and calcium, however, could produce calcium sulfate deposits, which are very difficult to descale.

Except for the recommendation to try CaCL2, I agree with other replies here. It's debatable whether you need either calcium or magnesium to extract a tasty espresso. You will find folks, including some very experienced coffee people that seem to have a taste preference for calcium, or for magnesium in their brewing water, but you won't find much agreement about that across different tasters and different coffees. Bicarbonate alkalinity is another matter though - you always want some of that to buffer acids and keep the water from being corrosive to your machine, and if you get too much it can dull the brightness of the coffee, especially in pourover. This dulling effect is much much less when it comes to espresso.



As to the main topic question here - What is the difference in flavor between Mg and Ca? I'll add my comments and some references FWIW.


The conventional wisdom has long been that you need some hardness minerals for optimum taste, but even that is not proven. One of the few controlled taste experiments on that was done by the folks at the Zurich University of Applied Sciences associated with the SCAE. You can get it from the members-only area of the SCA web site, and a freely available report can be found in the Winter 2016 issue of Cafe Europa, here : https://www.watertops.de/global/downloa ... _22-26.pdf .

The interesting takeaway from this study is that when they taste tested two different coffees in blind cuppings, with three expert tasters, at three different hardness levels, (where both hardness and alkalinity was reduced by a WAC resin decarbonizing softener) they did get some statistically significant results, but it was softest of the three that fared best. And that softest water was down at a GH:KH of about 52:22 CaCO3 equivalent - slightly out of the SCAE ideal brew zone recommendation. They did not try any water softer than that in their study.

There is also a commonsense argument from R. Pavlis, mentioned by Pressino in this thread: Since the liquid flowing through the puck is loaded with minerals, especially potassium and magnesium that comes from the ground coffee itself, any mineral that came in with the incoming brew water is a drop in the bucket. For example, a 30 ml espresso in an ash analysis contains about 25 mg of magnesium Even if you used a really hard 100 GH (CaCO3 equivalent) water recipe based on magnesium salts, the amount of magnesium ion that comes in with 30 ml of brewing water would be only 0.7 mg. Admittedly, the magnesium from the brewing water is all ion, and much of the magnesium from the coffee is likely bound or complexed to organic molecules. Also, the role that hardness minerals play in affecting extraction may happen primarily in the early wetting stage.

As to whether magnesium is better than calcium for taste, I think the old conventional wisdom was that calcium was somehow preferable. This is reflected in the 2011 SCAA water quality handbook, where it specifies an ideal calcium hardness and (on pg 36) warns about a high amount of magnesium hardness having a negative effect on coffee flavor. No supporting references or data for that. More modern conventional wisdom is the other way around, with unfounded claims about 'flavor enhancing magnesium' being commonplace. I think a lot of the modern pro-magnesium bias is due to the research paper by Hendon and Colonna-Dashwood and their subsequent 'Water for Coffee' book. The research paper, The Role of Dissolved Cations in Coffee Extraction did a number of binding energy calculations and concluded that "A compelling argument can be made for the favorable exchange of Ca2+ for Mg2+ to increase extraction yield, with no deficit to coffee flavor, and the additional benefit of removing the source of lime scale." But this effect on extraction yield with Mg rich water has been tested and not demonstrated in any refractometer experiments.


There is one taste experiment sponsored by BWT, and supposedly done by the folks at the Zurich University of Applied Sciences associated with the SCA. As far as I know this was never published as a paper, but a discussion can be found in the Winter 2016 Cafe Europa: https://www.watertops.de/global/downloa ... _22-26.pdf . In that experiment, they 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. That article lacks supporting data, statistics, even a named author, so must be taken with a grain of salt. There's some discussion of it here on HB: Calcium chloride vs. Magnesium sulfate