A Quirk in Brunwater?

[Tippsy-Turvy]

For my upcoming PM batch, the Brunwater spreadsheet recommended no acid additions inorder to achieve a 5.4 mash PH. This got me intrigued because the grain bill is mostly pilsner with only a little bit of the darker grains - usually some acid is recommended for my water.

So, out of interest I removed ALL the grains from the spreadsheet and ALL the mineral additions and the value for "estimated room temperature mash PH" was 5.8! With nothing added, shouldn't this value be just the untreated water PH?

Water Profile:
Ca 11
Mg 1
Na 7
Cl 9
SO4 12
HCO3 25
PH 8.4

Grain Bill (PM):
Pilsner 4lb
White wheat 7oz
Flaked wheat 7oz
Aromatic 7oz

 

[Doctor_M]

Edited: nm I see what you are getting at. I am sure Martin Brungard will be along shortly to give an explanation.

 

[mabrungard]

So, out of interest I removed ALL the grains from the spreadsheet and ALL the mineral additions and the value for "estimated room temperature mash PH" was 5.8! With nothing added, shouldn't this value be just the untreated water PH?

No, the malts themselves have a huge amount of buffering power that completely overwhelm the water pH effect. The problem is that typical pale colored malts produce a pH of around 5.7 to 5.8 in water with no alkalinity. Some external acidification (acid, acid malt, or Ca/Mg salt additions) is typically needed.

The response from the program is appropriate.

 

[Doctor_M]

No, the malts themselves have a huge amount of buffering power that completely overwhelm the water pH effect. The problem is that typical pale colored malts produce a pH of around 5.7 to 5.8 in water with no alkalinity. Some external acidification (acid, acid malt, or Ca/Mg salt additions) is typically needed.

The response from the program is appropriate.

I typed up an explanation similar to yours (well at least in spirit it was similar) then after posting it reread his post. He states "So, out of interest I removed ALL the grains from the spreadsheet and ALL the mineral additions"

 

[mabrungard]

Good point! If all the grain is taken out of the program, there is nothing to drive the calculation. The answer has no value at all under that condition. In addition, the water pH value is not used in any pH calculations. So it is not going to ever end up at the starting water pH.

Sorry for the confusion!

 

[Tippsy-Turvy]

Thanks for the responses, guys, and my apologies for causing the confusion.

What's causing my angst in the first place was the significant difference in recommended acid additions between Brewer's Friend and Brunwater for this upcoming brew.

From my experience, I've found that Brewer's Friend consistently overstates the acid addition amounts. So for the last couple of batches I ran Brunwater in parallel and found Brunwater's recommended acid amounts to be much more accurate. Usually, Brunwater's acid amounts are under half of Brewer's Friend's, for my brews.

HOWEVER, for this upcoming batch BF's recommended acid addition amount was quite high (which seemed to make sense to me given the grain bill) yet BW's was zero! I guess I can just take the average and see what happens.

 

[ajdelange]

So, out of interest I removed ALL the grains from the spreadsheet and ALL the mineral additions and the value for "estimated room temperature mash PH" was 5.8! With nothing added, shouldn't this value be just the untreated water PH?

Yes, it should. Your water and each of your grains should be treated in exactly the same way - as buffers. To get your water to mash pH protons (acid) has to be added. To get your base malts to mash pH protons (acid) has to be added. To get your chocolate malt (yes, I know there is no chocolate malt in this particular recipe - I am speaking generally) to mash pH protons have to be absorbed. Clearly the name of the game is to get the protons which need to be absorbed to be equal to the protons that need to be added.

Water Profile:
Ca 11
Mg 1
Na 7
Cl 9
SO4 12
HCO3 25
PH 8.4

Taking this at face value your water's alkalinity is 23 ppm as CaCO3 or 0.46 mEq/L. If you put a gal and a half of that (5.7 L for a total alkalinity of 5.7*0.46 = 2.62 mEq) in your mashtun and measure the pH it will, of course, be 8.4. If you then add 4 lbs of Pilsner malt which happens to be Weyermanns floor malted pilsner, stir and wait the pH (sample cooled to room temp) will be 5.88. In this case the malt has an intrinsic (DI mash pH) of 5.85. It is quite acidic compared to the water and has a larger buffering capacity than the water. It supplies 1.17 mEq of protons to the water at pH 5.88 whereas the water needs needs 1.87 to neutralize the alkalinity enough to lower pH to 5.88. The rest of the necessary protons are supplied by the reaction between calcium and malt inorganic phosphate. The buffering capacity of the malt at this pH is 35 mEq/kg-pH and you have 1.8 times this as there are 1.8 kg of malt. The buffering of the water is way lower than this as it would only take 2.6 mEq to carry all this water all the way to pH 4.5.

Now if you use Weyermanns pneumatic pils the intrinsic pH is 6.62. Again the malt's buffering is much greater than the water's so the pH becomes 5.64 which is also close to the malt's intrinsic pH.

If we were to add in the other grist components we would come up with an overall estimate for your mash pH but we need models for the intrinsic pH's and buffering properties of each. But the point is that the water is as much a component of the mash as any other item. If, as in your case, it is low alkalinity water it is not a major player - like a small amount of some specialty malt but a spreadsheet should take it and its properties into account. And it really isn't hard to do. All the details are in the Palmer/Kaminsky book.

 

[Tippsy-Turvy]

Thanks AJ.