I just came across some of Dr. Hendon's presentations on Water for Coffee v2. I never read the first version (only read some summaries and watched their presentations on the subject) and I don't know if v2 will be a book. There is some great stuff, a tighter/refined ideal brew zone and some water recipes.

LINKS:
Dr. Christopher Hendon - Physical and Chemical Considerations in the Production of Coffee on the Establish Media YouTube channel - What he later describes as the WfC2 video: http://www.youtube.com/watch?v=5KDQEufoxnM
The new graph for Water For Coffee v2 on the video is discussed at ~1:05:30

These slides I found online, from his presentation to the American Chemical Society: https://www.google.com/url?sa=t&rct=j&q ... 9777yb6hO4

You can find on YouTube his May 15, 2020 presentation for SCA, Systematically Improving Espresso: Math and Experiment, which has some WfC2 slides at the beginning: http://www.youtube.com/watch?v=B-iw2reuMlg


I have two questions on the new ideal brew zone and I was wondering if anyone knew the answer.

Is the top axis of the graph the (mg/L / ppm) scale you would use if you performed a traditional KH test on your water?


He plotted the three water recipes on the graph, but I'm assuming if you used a mixture of both epsom salt and gypsum salt, that results in 40mg/L of Ca2+ and 6 mg/L of Mg2+, then you would plot the mixture as if it was only 50mg/L of Ca2+, right?

You should def check out the videos!

Thanks!

Arch wrote:Is the top axis of the graph the (mg/L / ppm) scale you would use if you performed a traditional KH test on your water?

Yes. At this range of alkalinity, all the alkalinity is due to bicarbonate ion and you can easily convert between the two. Multiply the [HCO₃⁻] in mg/L by 0.82 to get the alkalinity in mg/L CaCO₃ equivalents). (Note: At very high pH this would no longer be true because the alkalinity would be caused by two different ions - [HCO₃⁻] and [CO₃²⁻].)

Arch wrote:He plotted the three water recipes on the graph, but I'm assuming if you used a mixture of both epsom salt and gypsum salt, that results in 40mg/L of Ca2+ and 6 mg/L of Mg2+, then you would plot the mixture as if it was only 50mg/L of Ca2+, right?

No, you would not want to plot it in units of mg/L Ca²⁺. Since it's a mix of two ions with very different masses you need to either use units of mmol/L of divalent ion, or better yet the familiar unit of CaCO₃ equivalents. (You could also use French degrees, German degrees, grains per gallon, mEq/L, which are other familiar units of chemical equivalence.)

For example, 40 mg/L of [Ca²⁺] is 1.0 mmol/l, and 6 mg/L of [Mg²⁺ is 0.25 mmol/L so you'd do best to plot it as 1.25 mmol/l of [Ca²⁺] + [Mg²⁺] , or plot it at 125 mg/L of CaCO3 equivalent.

It is often recommended to use some unit of chemical equivalence for hardness and for alkalinity. The easiest and most familiar of these is units of mg/L CaCO₃ equivalent. For divalent ions like [Ca²⁺], [Mg²⁺], and [CO₃²⁻] you can simply divide CaCO₃ mg/L equivalent by 100 if you want to know mmol/L. For univalent ions like [HCO₃⁻] you divide by 50. Using the same unit for both hardness and alkalinity helps you see at a glance how much of the hardness is associated with scale-forming carbonates. If you use the same units for both, your so-called 'temporary hardness', or potential scale forming hardness, is roughly equal to either the hardness, or the alkalinity, whichever of the two is lower.

More geeky discussion of hardness and alkalinity units can be found here: Good references on water treatment for coffee/espresso

I should have mentioned in reference to your question above about KH that all the KH kits and even the 'carbonate hardness' and the 'temporary hardness' kits I've seen on the market are doing a simple alkalinity titration - adding a known amount of acid to the sample and using a color indicator with an endpoint at around pH 4.3, which is a point where the last of the bicarbonate (HCO₃⁻) ion has reacted with the H⁺ to form H₂O + CO₂ .

Then the number of drops are converted to a chemical equivalence measure, typically mg/L as CaCO₃ or °dKH. This measures the buffering capacity, i.e., the total alkalinity of the sample, which in natural water at pH from around 5 to 10 is largely due to bicarbonate HCO₃⁻ .

I always thought by V2 Hendon meant he will release a new book or something
Anyhow, I have switched to Volvic for a few months and wondered why it took so long for me to look at water. I guess coming from a soft water area before I moved to a hard water area meant it was never a priority for me
Now I have moved to peak water jugs mostly because I really don't like dragging kilos of water up to my flat