Bru'n Water Cation/Anion imbalance in custom water profiles

[Hannabrew]

I have made about 12 custom water profiles in BNW, all of which have resulted in tasty beers according to me and my peers.

However when I look at the custom water profiles at the bottom of the water adjustment tab, I just noticed the warning to make sure the cation/anion fields are green to ensure they're balanced however nearly all of mine show yellow for those fields.

What exactly does that mean?

FWIW, I mostly use 100% RO water and acidify with lactic acid when needed.

 

[Silver_Is_Money]

It means that published water profiles are often highly inaccurate representations of actual brewing water, as in any and all "real world" waters the negative and positive ions present must fully be in balance. Technically there is some wiggle room here, as numerous minerals not typically considered by brewers are also typically present in water, and their ions are generally missed by abbreviated brewing water reports, but in a vast majority of cases these are minor players with respect to ion imbalance, so any 'real world' waters cation/anion imbalance must be kept small.

https://mashmadeeasy.yolasite.com/

 

[Hannabrew]

I guess ultimately what I'm asking is if I am making up a water profile based on what I want my chloride to sulfite ratio to be and how much calcium I want, do I need to be concerned if it shows yellow in that field? For example, here's one that shows yellow but was a great fit for a NEIPA
50, 5, 10, 200, 100

 

[ajdelange]

The first thing you need to understand is that all physically realizeable waters are electrically balanced. Thus you cannot make an unbalanced water by adding salts to any real water you have. The second most important concept is that the distribution of electrical charge in any water that contains carbo in any form i.e. carbonic, bicarbonate or carbonate or any phosphate or any sulfate though carbo is well and away the most important player depends on pH. When the profiles for Brun water were put together it is clear that the author listed the calcium, magnesium, sodium, sulfate and chloride he wanted, added up their charges and found a large net positive number. Knowing that most natural waters contain bicarbonate he balanced this positive charge with bicarbonate intending that the brewer would add sodium bicarbonate to synthesize the profile. But the profile only balances at pH 8.3 (the pH at which most of the carbo in a solution is bicarbonate). If one adds bicarbonate to water the pH shifts depending on what is already in it and goes to 8.3 only if the water is initially ion free.

But turning to your numbers: I assume they mean 50 mg/L Ca++, 5 mg/L Mg++, 10 mg/L Na+ and 200 mg/L SO4-- and 100 mg/L Cl-. The question normally at this point would be "OK; here's the stuff he wants. Now what pH does he want it at and how much carbo is it going to take to balance at that pH?". In this case, you have sulfate and chloride to the extent of -7.81 mEq/L and only +2.91 mEq/L Ca++, Mg++ and Na+ to balance them. Those levels of anion require a lot more metal to balance them and you will never get to a realizable profile unless you are more realistic about the metal amounts. If you want sulfate at 200 and chloride at 100 and want to limit Mg++ to 5 mg/L you will have to accept Ca++ at 131.6 mg/L. You can't have anything you want. Cations and anions must be in balance and are also limited by the relative amounts found in the salts we use.

 

[Hannabrew]

That makes sense, but then I guess I don't understand how I am able to play with the numbers in BNW in the water adjustment tab to meet these unbalanced water profiles using RO water as a base. Am I not really meeting the numbers like I think I am or is there something I'm still missing?

Here is an example that is similar to those numbers I posted.

 

[ajdelange]

In this case you are asking for something much more reasonable. If we ask a program to do the absolute best it can (minimize the rmse in the logs of the ion concentrations , IOW to minimize percentage errors, considering all ions of equal importance) using common salts it comes up with

Salt/Acid/Base mg/gal Synth
CaCl2.2H2O 448.49
NaCl 244.17
MgCl2.6H2O 0.00
CaSO4.2H20 1268.88
MgSO4.7H20 0.00

which results in

Ion.........Target..Realized
Calcium 100 110.3355
Magnesium 0 0.0000
Sulfate 200 187.0550
Chloride 100.00 96.2794
Sodium 25.0000 25.3762

Not too bad, really but notice that you get more calcium and sodium than you asked for and less sulfate and chloride as is necessary to balance the charges.

 

[Hannabrew]

So it sounds like you're saying that if I don't have the cation/anion fields balanced in the target water profile section of BNW, then it's likely going to be challenging for me to hit those numbers in practice due to the imbalance...thus why they should be balanced to begin with.

Is that about right?

 

[ajdelange]

Yes, exactly. It's going to be impossible to hit the target if the target profile is not balanced or not balanced at the pH of interest. That's a big problem I have with the Brun profiles. They are only balanced at pH 8.3 and most people don't mash at pH 8.3

. One of the advantages of RO water is that you can assume that carbo is non existent. In that case it is only necessary that the other ions balance and pH is not important as long as pH 7 is OK for the target pH.

 

[Hannabrew]

Got it. Thanks as always AJ! Learn a bit more every day.