Water for Coffee, glitches in books

When experts tell you about water for coffee, their long presentation usually boils down to this message: "It's terribly complicated but what you should do is buy my filter system." 

From what I have studied (and forgotten) so far I have remembered that one needs active carbon in the filter to get rid of any unpleasant substances like chlorine and one needs to limit the amount of minerals in the water even though some are useful because they help extract coffee or at least make you taste the coffee better.  50-60ppm (parts per million) in minerals seems very good. A good filter takes out or replaces minerals that could build up as scale inside your espresso machine.

Also, a pH value that is around 7 (neutral, not acidic and not alkaline) is good to have and "pure" water, as in distilled water, sounds good but is actually the worst to have.

Book cover
Now there is a new book out, by Maxwell Colonna-Dashwood and Christopher H. Hendon and the title "Water for Coffee" sounds great. They cover much much more than you would expect, from nuclear fusion to homeopathy and it seems that mr Hendon wrote all the heavy stuff with Colonna-Dashwood adding enlightening remarks like "How cool is that?" in highlighted paragraphs sprinkled over the pages dense with formulas.

I hesitate to recommend the book though. Almost all of it is way over my head so I can't judge it but a few things that I do know about seem to be misrepresented in the book.

How much to warm up one gram of water?
The authors explain how water is remarkable in absorbing energy. They explain that 1L of water (1000cc, roughly 1000 grams) needs 1 calorie to raise its temperature by a single "degree".

They do not say what scale that "degree" is on, if it is Kelvin, Fahrenheit or Celsius.

I see that they almost get it right but not quite. It is like this:

  • The small calorie or gram calorie (symbol: cal) is the approximate amount of energy needed to raise the temperature of one gram of water by one degree Celsius at a pressure of one atmosphere.[1]

So it is one gram of water by one degree Celsius.  Not 1000 times as much!

If they had used a capital C, things would be almost correct but it makes you wonder what you can believe of what they say about details you can not easily verify. You might end up in a dangerous place.

Another very remarkable statement they make is about pressure. One generally extracts espresso at about 9 bar of pressure, which is a lot as one finds out when taking off the portafilter at full blast.

How to visualize this pressure?

Press hard

Diving deep into the ocean, the ear popping pressure increases with 1 bar per 200m according to the guys. 

So then, extracting coffee at 9 bar, the pressure would be equal to a depth of 1800m below the surface of the ocean! Down there the pressure is over 150 bar!! It's the deep sea level, at 5,900 feet people. 

If the authors were correct, one would need a nuclear submarine to produce a Nespresso. And we know that is not the case.

That is where I quit reading. There may be some good tips in the book, but you have to keep a margin in mind that whatever they say may have to be multiplied or divided by 1000 and then you're in the ball park.


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