Help with water additions

[cjalderman]

Alright, so I'm formulating the water profile for a Westy 12 clone that I'm brewing using the Brewer's Friend mash chem and water profile calculator. I'm using 8 lbs of belgian pilsner (3 gallon batch) for the decoction mash with rests at 129 (20min), 150 (90min), 170 (10min).
Mash water: 3.85 gal
Sparge water: 1.45 gal
Total Water: 5.3 gal
For a pre-boil volume of 4 gal to boil down to 3 gal. I should also say that I'm using distilled water and building the profile from the ground up.

Adding 1.2g gypsum, 1.6g epsom, and 2.1g calcium chloride to the strike water gives me an Estimated mash pH of 5.61. Which, to my understanding, is acceptable for this mash.

I have two questions:
1. How accurate is this pH calculator when using distilled water?
2. I need to add baking soda and chalk to raise the residual alkalinity to 120 ppm in the final beer. In the sparge/kettle salt addition section, does this online calculator use the sparge volume (1.45 gal) or pre-boil volume (4.0 gal) when determining the overall water report?

For clarification of the second question, I want to know if I should calculate the additions of baking soda and chalk myself using 4.0 gal and add them directly to the boil kettle. If so, should I use my pre-boil or post-boil volume? Thanks!

 

[ajdelange]

I'm using distilled water and building the profile from the ground up.

Adding 1.2g gypsum, 1.6g epsom, and 2.1g calcium chloride to the strike water gives me an Estimated mash pH of 5.61. Which, to my understanding, is acceptable for this mash.

Yes, that's probably acceptable but I would prefer to see it more like 5.5

I have two questions:
1. How accurate is this pH calculator when using distilled water?

That's a tough question to answer. First question is pH when? It changes over time as the mash progresses usually rising over 20 min or so before it settles in. In a comparison of three predictors (one of which was Brewer's Friend) I got (for different water and grist than yours) predictions of 5.61, 5.54 and 5.46. The last number was obtained using actual titration data of the 3 malts in question so one might have a bit more confidence in it than the other 2 which use general characterisitics of the malts. One interesting observation is that by tweaking added acid in the calculators one can compute their assumed grist buffering capacities. Both the popular spreadsheets predict a grist buffering of -37 mEq/kg-pH. The measured data indicate that this grist would have buffering capacity of -52.6 mEq/kg-pH. I'm guessing that the pH you would observe (which is what you really should do - not rely on a calculation) would be within ±0.15 pH of what a calculator would tell you depending on several factors (when you measure, the particular maltsters and malt lot numbers etc.).

2. I need to add baking soda and chalk to raise the residual alkalinity to 120 ppm in the final beer.

I don't know anything about this beer but I cannot imagine that adding baking soda and chalk to it at any point would benefit you. In fact you should be adding acid (or acid malt) to the mash in order to get a pH close to 5.5. This should be verified by a pH meter reading but with a pure Pils malt grist some acid (2-3% sauermalz) will be needed. Your boil will probably finish with a pH of 5.2 - 5.4. You don't want to go into the fermenter higher than that.

In the sparge/kettle salt addition section, does this online calculator use the sparge volume (1.45 gal) or pre-boil volume (4.0 gal) when determining the overall water report?

I am not familiar enough with that calculator to say anything beyond that you most probably do not want to add alkali to this beer at any point in the process. In any case, where alkali is required (beers with a lot of dark malts) chalk is a poor choice.