Mash pH gut check

[JonM]

Hey everyone!

I'm brewing an ESB later on today. My recipe is (5.5 gallons) 11 lbs Maris Otter (4 Lovibond) .84 lbs. English Medium Crystal (60 L) and .28 lbs. extra dark English Crystal (160 L). I'm mashing at 1.33 qts/pound. My water, built from RO, is:

Ca 50
Mg 0
Na 19
Cl 60
So4 73

That comes from 4 grams of gypsum, 1.5 g Kosher salt, and 2 g of CaCl.

Brewers friend calculated a predicted mash pH of 5.4. I did a test mash and the mash pH, with a calibrated pH meter, was below 5.2. It was something like 5.16 or so. Obviously that needs to come up by at least .2. Brewers Friend tells me that if I add 1.5 g of calcium hydroxide, its predicted pH goes up by about .2, so that should get me in the ball park, right?

My real question is: 1.5 g of calcium hydroxide sure seems like a lot. I don't want to use baking soda b/c I have plenty of sodium already. Does this sound like a sensible plan or am I missing something obvious? Thanks all!

 

[The_Bishop]

I don't see how that grist can hit so low a pH. What meter? What temperature was the sample?

 

[JonM]

I'm puzzled too. It's the Thermoworks 8689 which I know isn't as good as the Milwaukee or Hach meters, but it has a reasonably new electrode (4 months old) and it was calibrated right before I did the test mash.

 

[ajdelange]

Those numbers just aren't reasonable. Your grist is 90% Maris Otter which has a DI mash pH of 5.6 - 5.7 and your dark malts are neither that potent nor present in large enough quantity to get you to pH 5.4 let alone pH 5.2. More realistically the mash pH should be about 0.05 below the base malt DI pH so you might want to check the base malts DI mash pH. To get 11 pounds of MO to pH 5.4 would take 70 mEq of protons and those quantities of dark malts of those colors can only provide approximately 22. The typical spreadsheet would give you another 11 for the calcium but half that is more realistic.

In cases like this always suspect the pH reading. Calibrate the meter with fresh buffers, then wait twenty minutes or so and check its readings in the buffers again. It may be drifting. Another possibility is that you didn't wait long enough or stir the test mash adequately. If the dark malts are clumped in one area and you put the electrode in that area you measure the pH of the dark malts more than the base malt and off readings are possible.

If the meter passes cal and stability tests and the test mash is well mixed and has been allowed to stand long enough for the dark malts' protons to be dispersed and absorbed then you have super dark malts i.e. ones that produce several times the numbers of protons they can reasonably be expected to produce.

Were your pH really 5.2 you would have about 100 mEq of unexplained protons to deal with. 1.5 grams of Ca(OH2) would only neutralize 40 of those.

 

[JonM]

Excellent - thanks as always, A.J. I'll recalibrate and give the mash plenty of time and plenty of stirring.

EDIT: Oh, and I'll leave out the calcium hydroxide.

 

[JonM]

Hey everyone! Thanks again for all the good advice. I followed A.J.'s recommendations and got some fresh single-use packages of 4.01 and 7.01 buffer, re-calibrated, and then proceeded with the mash. Oddly enough, several samples from the mash landed right around 5.32. So I guess I must have gotten some kind of super high Lovibond grains or maybe some other oddball thing with the grains. I think this batch will be just fine, but the mystery will continue ...

Thanks again!

 

[ajdelange]

That's moving in the right direction but those quantities of colored malt just aren't enough to move a typical ale malt that far so perhaps you have an atypical ale malt. That's why I suggested a check of its DI mash pH. To reach 5.32 assuming that the colored malts are typical would require a base malt DI pH of about 5.45 which is more typical of a Munich malt.

I still suspect the pH reading. I always do in cases like this. Did the electrode pass the stability test?