Can someone just check my idiot-level mathematics here? I'm slightly losing it.
I'm trying to work out how to make the 70/30 water directly into five gallons of distilled, rather than by making concentrates.

The recipe says to make two 1000ml concentrate bottles with 14g of sodium bicarbonate in one, and 12g of magnesium sulphate in the other.
Then take 5ml from each to add to 1000ml of fresh distilled water.

So that's 0.5% of the concentrates going into the main mix. Which means 0.07g of bicarbonate and 0.06g of magnesium.

Five US gallons is 18,927ml, which is therefore 18.927x more than 1000ml.

0.07g x 18.927 = 1.32g
0.06g x 18.927 = 1.14g

So, if I just put 1.32g of bicarbonate (I'm going to try potassium since that is what I have) and 1.14g of magnesium sulfate in five gallons of distilled water, does that work out correctly?

Yes.

Even at 5 gallon capacity it would think it would be very difficult to accurately measure out 1.14g of something. You must have better scales than me!

Shojin wrote:Can someone just check my idiot-level mathematics here? I'm slightly losing it.
I'm trying to work out how to make the 70/30 water directly into five gallons of distilled, rather than by making concentrates.

The recipe says to make two 1000ml concentrate bottles with 14g of sodium bicarbonate in one, and 12g of magnesium sulphate in the other.
Then take 5ml from each to add to 1000ml of fresh distilled water.

So that's 0.5% of the concentrates going into the main mix. Which means 0.07g of bicarbonate and 0.06g of magnesium.

Five US gallons is 18,927ml, which is therefore 18.927x more than 1000ml.

0.07g x 18.927 = 1.32g
0.06g x 18.927 = 1.14g

So, if I just put 1.32g of bicarbonate (I'm going to try potassium since that is what I have) and 1.14g of magnesium sulfate in five gallons of distilled water, does that work out correctly?

If your using potassium bi, then you actually need a little bit more than their recipe. Where their recipe using sod. bi. would call for 14g, you would swap 16.8g of potassium to get the same 42PPM alkalinity. OR, if you use 14g, you will just end up with 35ish PPM alkalinity.

Kind of splitting hairs really.

Thanks for that - I'll adjust accordingly.

1.59g potassium bicarbonate
1.14g magnesium sulphate

Does anyone know what the hardness and alkalinity is of the recipe that TWW uses?

They say they use the following for one gallon :

Espresso 1500mg
Magnesium Sulfate 1050mg
Calcium Citrate 300mg
Potassium Bicarbonate 150mg

So for example, does that mean a TWW mix would have 5.25 grams of magnesium sulphate in 5 gallons (5x1050mg) vs the 1.14 for 70/30.
And the Potassium Bicarbonate would be only .75grams vs the 1.59 grams. How would one convert these amounts into the final hardness and alkalinity figures?

So the resulting values between the two would end up quite different I am guessing and I was trying to compare the end results of the two. Maybe I am trying to figure out where TWW fits on Pat's chart here:

Good references on water treatment for coffee/espresso


Thanks in advance for sharing your knowledge.

CarefreeBuzzBuzz wrote:So for example, does that mean a TWW mix would have 5.25 grams of magnesium sulphate in 5 gallons (5x1050mg) vs the 1.14 for 70/30.
And the Potassium Bicarbonate would be only .75grams vs the 1.59 grams. How would one convert these amounts into the final hardness and alkalinity figures?

Yes. Compared to 70/30, TWW would have about half the bicarbonate and over 4x the Epsom (magnesium sulfate heptahydrate)

Taylor Minor has said that his magnesium sulfate is indeed ground epsom (the heptahydrate), and if we assume that his calcium citrate is the tetrahydrate the calculations give you:
magnesium hardness: 113 mg/L as CaCO3
calcium hardness: 42 mg/L as CaCO3
bicarbonate alkalinity: 20 mg/L as CaCO3
sulfate ion: 108 mg/L

And that would put it on that chart somewhere around 155 for total hardness and 20 for total carbonate/bicarbonate alkalinity. (I assume that any acid buffering from calcium citrate would have neglibile effect on total alkalinity.) **

** Edit addition: After thinking and looking at the pKa values for citric acid, and considering what Taylor Miner has said about his alkalinity measures, I think the calcium citrate would affect a standard alkalinity test titration by about 14 mg/L as CaCO3. I base my estimate on 300 mg/gallon of the calcium citrate tetrahydrate (0.14 mmol/L) and figure about 2 protons per mole of the triprotic citric acid has reacted when the titration hits the pH 4.3 endpoint of a standard alkalinity titration. So you could place that TWW espresso water at 155 : 34 on the hardness vs. alkalinity chart. But if scaling is your concern, the alkalinity of 20 mg/L is the proper value to go by. When you start adding odd things like calcium citrate to a water all the usual assumptions about the predicted effects of an alkalinity measurement go awry.

Pat,

thank you I really appreciate your response. That is really interesting where this comes out then on your chart. It's somewhat of an outlier sitting low on the alkalinity, high on the hardness but in your light green no scale zone. Both those values outside of the SCA Acceptable Range on both but within the SCA Adequate Brew for alkalinity. So I guess it's a matter of taste so long as it's not scaling your machine.

I kinda see why people seem to gravitate to an easy method so long as they don't have scale given the long list of other variables that impact the taste of coffee.

Michael

I have used the Bru'n Water spreadsheet by mixing up 21 L at a time. Water basically weighs 1 kg per liter.

In this example I used 1.3 g of Epsom Salt and 1.5 g of Baking Soda for a 70/30 mix.

Like the scientific point of view we put in to get our water right.



Not sure what results you got with going straight to 5 gals but I didn't fair so well. It is such a small of amount of salts that I felt the water was over concentrated. Then I had to dilute which was a pain