homeburrero wrote:To Buckley - did you shake and aerate the sample real good before testing your water mix? If not, that might have affected your pH and alkalinity numbers a little.

No. I just used a casual aquarium pH test kit and that was not mentioned in the directions. Also, the kit's upper limit is 7.4 and it states that that limit will appear even if the actual pH is higher than 7.4, so I do not know the actual pH. I am thinking that shaking would only affect the volitile components, carbon dioxide and ammonia. I think that the former would be in equilibrium readily and that the latter would be nonexistent. Please bear in mind - and this will affect your calculations - that Zerowater and distilled water are slightly acidic. The Zerowater I started with was variably 6.3 - 6.4 pH.
As far as the two-ampoule packaging, I am not up on my chemistry sufficiently to presume that putting everything in one package would force precipitation but I wonder if GCW is listing all of its ingredients? After all, what governmental agency or individual is going to bother to send GCW through a gas chromatograph?

BT

If the SCAA profile is available THIS may help to calculate the amount of common salts to add RO water to get you close. I use it all the time for homebrewing beer, but never thought about for brewing coffee. Something I may have to look in to...

Thank you. I will look into it...
BT

You're welcome!

FWIW, here is a recent and an older thread from two different homebrew forums with discussion on "building" coffee brewing water from RO.

http://www.homebrewtalk.com/showthread.php?t=519983
https://www.homebrewersassociation.org/ ... ic=22274.0

We can definitely help you build coffee water but the topic on hand deals with the gcw.

The only thing I struggle with is calculating pH. I have a meter but it always seems off the charts

brianl wrote:We can definitely help you build coffee water but the topic on hand deals with the gcw.

Yes. Last time it came up on HB was here: Water formula I think a lot was discussed there but never arrived at a simple formula for adding pickle crisp and baking soda to distilled in order to hit SCAA standards. Even though it's a bit off topic, I'll bite and provide what I think is a formula below.

brianl wrote:The only thing I struggle with is calculating pH.

Same here. I did Henderson-Hasselbach calculations for blood chemistry ages ago in biochemistry classes, but not even sure they apply here. Dang CO2 enters into the equation, which affects the bicarbonate/alkalinity as well as the pH.



Off Topic stuff follows:
What would I add to distilled in order to get close to the SCAA target of:
Calcium hardness - 68 mg/l (as CaCO3) (= 27 mg/l Ca++)
Alkalinity - 40 mg/l (as CaCO3) ( = 49 mg/l HCO3-)
Sodium - 10 mg/l (OK if less than 30 mg/l)
TDS - 150 mg/l (75 - 250 mg/l OK)
pH - 6.5 - 7.5

So doing a crude calculation, and using just calcium chloride* and baking soda, I came up with the following, using yet another of our beer-brewing brother's handy calculators:


From calculator at http://www.brewersfriend.com/water-chemistry/


Note that we are talking 10 gallons here, juts half a teaspoon of baking soda does 10 gallons!

Alas, this calculator also doesn't try to do the pH calculation. I'm guessing it might come out on the basic (high side) of the SCAA ideal. That's OK, since we have a chloride level of 47 mg/l and we don't want to worry about corrosion. The TDS should come out in the ballbark since we are adding 6.3 grams of stuff to 10 gallons, which would be about 165 mg/l, and in practice would be a smidgen less because of some HCO3 converting to CO2/H2O.

If I were doing this (making coffee water out of minerals and distilled) I think I might go with a bit less Ca++ and add some Mg++. SCAA water spec doesn't say anything about Mg, but some believe it to enhance the extraction better than Ca++.

P.S.
I did try out the nice speadsheet that Fred (MerlinWorkd) provided but couldnt get it to behave on my Mac's Numbers app

*Note: The calculator app doesn't specify what form of CaCl2 it expects, but the Ca++ concentration comes out right if you assume that it is pure dihydrate, i.e. 2 H20 molecules are associated with each CaCl2. Pickle Crisp I believe is dihydrate CaCl2.

Ooops got a little carried away, apologies for the OT...

No need at all for apology - I think we all appreciated your posts, and they were closely related even if not specific to GCW.

oh wow. that calculator is great. I only have Potassium Bicarb in my possession but might have to get more to experiment!

I made espresso water yesterday (source tap water is 160TDS with 140 GH that is mostly calcium and some magnesium as is filtered through the Berkey which doesn't change any of this composition). I add Distilled water with a ZeroWater filter until the TDS comes down to 50ppm. At this point the hardness is around 34-40ppm. I then add drops of my 10% strength potassium bicarb solution to raise the TDS to 100. The resulting GH stays at 34-40ppm but the alkalinity (kH) is raised to about 60-70ppm. I thought about trying to reduce the KH but would rather be more alkaline for the copper boilers.

This is all eyeballing chemistry but I'd love to be able to make it based on a recipe. I always found the SCAA standards to be interesting as the alkalinity/hardness/ph are all interconnected. Therefore, keeping the hardness at 70ppm while the alkalinity is at 40ppm. or maybe I'm missing something basic. I'm sure my potassium bicarb raise the alkalinity too much and i'd be better using something else to stay above 50ppm KH without dropping my TDS or adding hardness (usually when my hardness is at 50 or lower the alkalinity drops to around 40ish).

The brew water is just straight filtered water.

This post:

dilin wrote: Water recipe from Five Senses:

https://s3-ap-southeast-2.amazonaws.com ... recipe.pdf

For a more in-depth read,
http://www.fivesenses.com.au/blog/2014/ ... -on-coffee

For those who are really interested, I can post up the journal paper later.

HTH.

Was originally posted here, and it caused a new discussion on the topic of 70/30 water. So I moved/merged dilin's post and four or five subsequent posts related specifically to 70/30 Water over there: 70/30 Water