Brewfather and water additions

[Doublediamond]

I've been having a play with the Brewerfathers water calculator. I'm using 75% RO water and 25% tap water. The tap water has been tested for calcium and alkalinity and I got the rest of the information from my online water report.
I want to brew a David Heath Kolsch recipe, so I entered his target profile.
Using the auto function I was spot on with only a few additions needed.
However the mash PH was in the red at 5.7 and I wanted 5.3 ish. I manually added some CRS to lower the Ph but this knocked my HC03 level out .
Tried adding lactic and this seemed to work.
So, why does Adding lactic not affect any of my profile figures , but CRS does?
Sorry for the long winded question and I'm anticipating the replies of, just brew it!
Any help would be appreciated.

 

[AJA]

Both CRS and Lactic acid will reduce the alkalinity HCO3- in the same way. They are both acids after all. The difference is the counter-ions.
Lactic acid will add lactate ions, which have a low taste threshold for some.
CRS adds Cl- and SO42-, which you'll need to factor into your water profile. Cl- adds softness and mouthfeel , So4 2- adds more 'hoppiness'.

 

[stripeyjoe]

I have also noticed that adding Lactic acid does not reduce the HCO3 levels in Brewfather, only the pH. Not sure if that is correct or not.

 

[Doublediamond]

Thanks for the quick reply.
I've used both CRS and Lactic in previous brews in the way you suggested said, and depending on the style which one to use.
I must be doing something wrong on Brewfather, when I add Lactic to the mash it doesn't alter the profile, but does lower the PH.
The auto button does does get me to the target profile but the Ph is in the red.
My home water profile is
Ca 90, Mg 23, Na 26, Cl 31 So4 59 Hco33 233
I plan to dilute with 75% RO water.
My target profile is Ca 37, Mg 19, Na 25, Cl 31, So4 0 Hc033 80

 

[stripeyjoe]

There's a Brewfather forum on facebook which the developer is active in, might be worth asking why Lactic additions do not lower HCO3 levels and only lower pH.

 

[Doublediamond]

I've heard of a few interesting forums on Facebook, not on it though.

 

[stripeyjoe]

I asked the question and this was the first reply…
lactic acid is a weak acid. bicarb is a weak base. depending on how much lactic acid you add there might be eventually enough free H+ ion to convert the hco3- to h2co3, which is in equilibrium with h20 and co2. For a small enough addition of acid, there may not be enough free h+ added to significantly shift the equilibrium H2co3 towaru H20 plus Co2. this is an application of Le chatelier principle.