Folks, please be mindful about posting copyrighted material without permission. I've removed said post.

I'm going need you to remove your image link here.

Absolutely, positively, NO.

You need to understand the complete context in which it was written which evidently, you do not, even given your accomplished educational CV.

I'll leave it to others . . . no offence Tom C.

Eric makes a good point, it would be perfectly acceptable to post an equation. I just don't want to see the thread derail into the same debacle we've had with a particular refractometer manufacturer.

I'll defer everything else from here to Dan.

I am sorry erics and TomC, but our stipulations are very clear on the inner front cover.

To reiterate:
Copyright © 2015 by Maxwell Colonna-Dashwood and Christopher H. Hendon.
All rights reserved. No part of this work covered by the copyright may be reproduced or used in any form or by any means - graphics, electronic, or mechanical (including photocopying, scanning, recording, taping, photographing) reproductions - without permission of both of the authors (M. Colonna-Dashwood and C. H. Hendon).

*****************This very clearly states that you cannot scan any part of the book and reproduce it online. You are free, of course to talk all you want about the book, include equations, because of course you can derive those yourself. But you included my typesetting, and my prose that accompanied it is a violation. First of all, the IP belongs to Maxwell and I, and secondly you don't have the license to publish, even with no financial benefit, the type face used.***************************

I am appreciative of your interest in our work, and I encourage you to email me if you'd like to discuss anything further, or any specifics relating to content of the book.


Regarding other people's comments about page 24's content:
What seems to be the problem?
Whilst water is not an ideal gas (obviously), static pressure does not really apply to water. Your espresso machine pumps at, for instance, 9 bar. But this is not 9 bar of something tangible because I can achieve the same effective pressure by simply modulating the aperture of the pipe. The only thing you can actually measure and that is actually determined is the flow rate of the water out of the group.

Far from being constant, the static pressure of an incompressible fluid will adjust instantaneously (well, at the speed of sound) to applied forces. Consider a closed rigid cylindrical vessel, filled with water, whose top side consists of a weighted piston, free to move in the cylinder. Place the whole apparatus in a vacuum chamber. The pressure of the water will equal the weight on the piston divided by its surface area. It has to be, it's providing the equal and opposite reaction which stops the piston falling.

Apologies for causing offence, the comment was meant as a light hearted criticism of an otherwise outstanding book. My espresso this morning, brewed with some salts added to an otherwise uninspiring bottled water, to bring it into your ideal brew zone, was excellent - the most balanced and full extraction I've had of that particular coffee - and for that I thank you and Maxwell.

Ah yes, indeed! I suppose that we went for a simplification here to illustrate that if course you can pressurize water (I.e. A hydrolic piston) and the energy associated with this change in volume (or lack thereof) makes water ideal for such an application: under large amounts of pressure not much volume changes. In other words, potential energy increases, but per molecule the material is vastly the same. If you then open the pipe the kinetic energy of each water molecule increases with potential decreasing. I suppose I just think of this problem as 'where is the energy stored' and, whilst not physically correct, the idea that the piston is elevated (assuming no load besides the piston to make things simple) then the potential energy is indeed stored in the piston (as it is elevated). I absolutely acknowledge that this is not strictly correct but it makes the discussions with people about pressure in an espresso machine - what they ultimately care about - more tangible for the untrained. I am pleased to hear that you read it in such detail with a sceptics mind. This is not offensive but rather the ultimate compliment!

Regarding your coffee this morning: awesome! What coffee was it? Who roasted it?

It was an Ethiopian, Liya Guji roasted by Rave. I have tried a few brews now as well and am beginning to see a consistent picture of a massive fruit hit, but some undesirable artifacts also. I've exchanged emails with Maxwell, as I mentioned earlier in the thread, and this was very helpful but can I make a final sanity check on your units, particularly Ca vs Mg? If I had a solution containing 1 mmol/L each of calcium, magnesium and bicarbonate ions it would be at GH=80,KH=61 on your figure yes? Ie the calcium and bicarbonate as their actual weight and the magnesium scaled up by 1.5ish. (This is not what I'm using for brewing.)

Perhaps the discussion on pressure would be best elsewhere. However, I should point out that water stores very little energy by virtue of its (static) pressure. Since the volume change is tiny, it takes very little work to pressurise it in the first place. This is why large pressure vessels are normally tested with liquids first - if they fail there is only the gravitational potential energy of the fluid to be dissipated, which just leaves a puddle!

Ta!

Edit: For the benefit of anyone following this thread, it might help with the context to give the composition of the water I've been trying. As mg/L it's

Calcium 18
Magnesium 70
Sodium 12
Bicarbonate 40

plus lots of Chloride and Sulfate, and a bit of Nitrate, to make it all add up.

Maybe I just need to read more of the book, but I'm having a hard time understanding how GH and KH relate to what stats my local water quality report gives, which are:

pH, standard units 7.59
Alkalinity, mg/l 24.52
Hardness, mg/l 4.81
Sodium, mg/l 13.9

The junky little handheld meters usually say between 30-40ppm TDS.

edit: I see that Alkalinity is KH and Harndess is GH. I also see that all water I've used has been closer to "point C" as per the book. Very curious!

Ok... looking at Water for Coffee, I'm reminded of the 70 30 water that was discussed about a year ago?

My notes for 70 30 water were to add to distilled water:
0.264g/gal baking soda
0.227g/gal epson salts

And with regards to Water for Coffee (not to be mistaken for a synopsis; I barely have an understanding!) add:
0.287g/gal baking soda
4.779g/gal epson slats

Looking forward to trying this out soon.

endlesscycles wrote: And with regards to Water for Coffee (not to be mistaken for a synopsis; I barely have an understanding!) add:
0.287g/gal baking soda
4.779g/gal epson slats

Looking forward to trying this out soon.

Not sure you really want to try that as that will result in extremely high sulfate levels in your water. At least double check the recommended formula before proceeding.

According to my quick calculations 4.8g of Epsom salt per gallon = 1.27g per liter. Epsom salts are magnesium sulfate (MgSO4). By molecular weight it is approximately a 1:4 ratio of Mg to SO4. So that means you are getting approximately 250mg per liter (250 ppm) of magnesium and 1000mg per liter (1000 ppm) of sulfate. That seems really high for both.

According to what I've read anything above 250 ppm of sulfate is very corrosive, particularly to copper which just so happens to make up a lot of your average espresso machine. For this reason LM recommends a maximum of 50 mg per liter of sulfate. Also, at those levels in drinking water sulfate can cause a laxative effect, so you may experience diarrhea. Fun stuff!! Chloride is also very hard on espresso machines, particularly stainless steel, and can cause corrosion problems, so you will want to pay close attention to that as well.

The goal is to find the right balance between water that yields a good tasting extraction but is also safe for equipment and human consumption.