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Using Residual Alkalinity to Estimate Required Wort Color to Hit Mash pH Targets

biertourist

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I'm following the article on the BeerSmith blog about calculating water Residual Alkalinity; I've entered the numbers for Seattle water using the built-in average profile in BeerSmith, then I'm trying to use the formulas from the article to estimate the "low_color_SRM" and "High-color_SRM".

I THINK I'm doing it right, but the low color numbers are slightly strange.
(Mostly I'm looking for a "Warm and fuzzy feeling" that you get when someone can confirm that you're doing it right, or point out where you went wrong.


BeerSmith's Water Profile info for Seattle:
CA=17 ppm
Mg = 1 ppm
Na = 4 ppm
Sulfate = 2 ppm
Chloride = 4 ppm
Bicarbonate = 18 ppm

The built-in Analysis generates results all as ppm as CaCO3:
Alkalinity: 15 ppm
Effective Hardness: 13 ppm
Residual Alkalinity: 2 ppm


Using the formulas in the article and "showing my work":
ormula for Effective Hardness if you have Ca and Mg in PPM:
Effective_Hardness = Ca_ppm / 1.4 + Mg_ppm/1.7
Effective Hardness = 17/1.4 + 1/1.7 17/1.4=12.1429 1/1.7=0.5882
Effective Hardness = 12.14 + .59
Effective Hardness = 12.73


Formula for Residual Alkalinity if you have Effective Hardness (above) and Alkalinity as CACO3
Residual Alkalinity = Alkalinity as CaCO3 - Effective Hardness
Residual Alkalinity = 15 - 12.73=
Residual Alkalinity = 2.27

Alternative Formula if you don't have Alkalinity as CaCO3 and instead have only Bicarbonate (HCO3) in ppm:
Residual Alkalinity = (50*Bicarbonate)/61 - Effective Hardness
Residual Alkalinity = (50*18)/61 - 12.73
Residual Alkalinity = (900) / 61 - 12.73
Residual Alkalinity = 14.75-12.73=2.02
Residual Alkalinity = 2.02



Rough Wort Color Requirement to hit mash pH in 5.2-5.4 range Formula (Palmer): (Works is RA is reasonable and above -128)
Low_color_SRM = RA*0.082 +5.2
High_color_SRM = (RA + 122.4)/ 12.2

Low_Color_SRM = (2.02*0.082)/ 12.2
Low_Color_SRM= 0.1656/12.2=0.0136
Low_Color_SRM= 0.0136 SRM

High_Color_SRM= (2.02+122.4)/12.2
High_Color_SRM= (124.42/12.2=10.1984

High_Color_SRM= 10.2 SRM



If I'm interpreting this correctly, it means that if your water profile exactly matches the Seattle profile in BeerSmith, that your beer's mash pH would land in the range of 5.2-5.4 if your malt color range is somewhere in the range of 0 SRM to 10.2 SRM.

My understanding is that this is a pretty rough guesstimate there's lots of things not accounted for including specific gravity and variations in the acidity provided by different color malts and malts between maltsters and probably loads of other things, but really cool to just play with the rough map and see how the different waters alter things...


Adam
 
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