missing pH target

[monkeyman1000]

Hello, this is my third batch since getting my pH meter. I have missed by calculated pH every time by at least .18. Today I am brewing (BIAB) a sweet stout. Grain bill is:
Marris Otter 3.44#
Black Patent .35#
Crystal 75 .26#
Chocolate .17#
I am using store bought RO and I don't have a TDS meter yet. I added:
0.6 grams Gypsum, 0.9 grams CaCl2 and 0.6 grams pickling lime to 3.2 gallons of water.
Bru'n water predicted a 5.6 pH at room temp with a starting water profile of
Ca 59.2
Mg 0
Na 8
Sulfate 29
Chloride 41
Bicarb 94.3
Alk 78
RA 36

Brewer's friend was pretty close to this with a predicted pH of 5.51.
My actuals were
At 15' 5.45 at 72.7 F
at 30' 5.41 at 71.4
at 45 5.38 at 73.7F

Am I doing something wrong or is there something off with the RO water I am using? I am getting a TDS meter soon but will be off to the next city before I get to brew again. Thanks in advance for the help.

 

[monkeyman1000]

Also, I am using the Hach pro+ Ph meter. I calibrated about 30 minutes before my first sample. Stability check was good. I had also calibrated it last weekend to help a friend brew and it was pretty close when I calibrated it today. I feel confident in the meter.

 

[GotPushrods]

Am I doing something wrong or is there something off with the RO water I am using?

I doubt it. That is a little like being confused why the hurricane didn't make landfall exactly where model #27b predicted.

These are MODELS for PREDICTION... as long as you're comfortable with your meter and you are confident in it's stability, take comfort in knowing these models will never be perfect every time. FYI, I'd be happier with your actual recorded pH than predicted anyway.

 

[monkeyman1000]

Thanks for the reply, I shot higher on the spreadsheets due to my actual pH coming in low for the last 2 brews. All in all a decent brew day.

 

[mabrungard]

Hello, this is my third batch since getting my pH meter. I have missed by calculated pH every time by at least .18. Today I am brewing (BIAB) a sweet stout. Grain bill is:
Marris Otter 3.44#
Black Patent .35#
Crystal 75 .26#
Chocolate .17#
I am using store bought RO and I don't have a TDS meter yet. I added:
0.6 grams Gypsum, 0.9 grams CaCl2 and 0.6 grams pickling lime to 3.2 gallons of water.
Bru'n water predicted a 5.6 pH at room temp with a starting water profile of
Ca 59.2
Mg 0
Na 8
Sulfate 29
Chloride 41
Bicarb 94.3
Alk 78
RA 36

Brewer's friend was pretty close to this with a predicted pH of 5.51.
My actuals were
At 15' 5.45 at 72.7 F
at 30' 5.41 at 71.4
at 45 5.38 at 73.7F

Am I doing something wrong or is there something off with the RO water I am using? I am getting a TDS meter soon but will be off to the next city before I get to brew again. Thanks in advance for the help.

That is an odd result. All the reports I've had for brewers with acidic grists is that Bru'n Water tends to underpredict the mash pH, meaning that the actual pH was higher than the low pH Bru'n Water predicted.

One thing to note is that pickling lime can go bad. It reverts back into calcium carbonate if it is exposed to moist air. If you have some acid on hand, you can check the potency of the lime with a simple test. Place a small amount of lime in a bowl and then drip the acid onto it. Be careful since the reaction does generate heat. But if the lime is pure, the acid will completely dissolve the lime and there WON'T be any fizzing. If there is fizzing, then part of that lime is actually in the form of calcium carbonate. If the lime doesn't dissolve fully, then there is some other substance in the lime and its just taking up volume.

 

[monkeyman1000]

Thanks for the reply, I just bought the pickling lime yesterday at my LHBS and it was in a sealed container. I will try acid test though. Would vinegar work to perform the test?
The last 3 brews I did came in under the predicted pH value of the spreadsheets.

 

[mabrungard]

Yes, vinegar would work. If the lime fizzes, it is not pure.

 

[ajdelange]

Vinegar is plenty acidic enough to make calcium carbonate fizz but I doubt very much that this is the problem. Calcium carbonate, with respect to mash pH, is nearly as strong a base as caclium hydroxide (15.9 mEq proton deficit vs 16.2 for the lime in this case) but it does take longer to react - quite long in some cases. In a new, sealed package you shouldn't have any CaCO3 anyway.

What you have observed is rather mysterious. Models are models and their shortcomings have been pointed out here already. FWIW I'd predict 5.56 for what you have specified. I don't have data on your particular malts and so must make some assumptions but if I play games with the numbers I have to do pretty dramatic things to get to predicted pH as low as 5.4. The base malt, for example, would have to have a DI mash pH of pretty close to 5.4 and that's not reasonable. Fiddling with the parameters of the colored malts requires equally unlikely values to support a pH as low as 5.4.

The long pole in the tent here is the lime. That is a lot of lime. It's proton deficit, to pH 5.56, is 16.2 mE which is four times that of the base malt and about equal to the sum of the acidities of the colored malts. That is enough to shift the pH by almost 0.2 (based on assumptions about the overall grist buffering capacity). Thus I think Martin is right to suspect the lime but my guess would be a problem in measuring it out rather than it losing it's strength.

In any case I think the message here is that one should, having verified that he can trust his meter, that he should trust his meter rather than predictions.

 

[GotPushrods]

Thus I think Martin is right to suspect the lime but my guess would be a problem in measuring it out rather than it losing it's strength.

I agree. Put a nickel on your scale. Does it read 5.00 g?

 

[monkeyman1000]

I calibrated the scale with a 500g weight per the instructions it came with but haven't tried the nickel yet. I didn't get any fizzing with the vinegar either so the lime seems okay. I will try the nickel tonight when I get home. Thanks again for the replies.

 

[monkeyman1000]

I put a 2007 nickel on the scale and it read 5.0 grams. Let the mystery continue. Could the water I'm using from the store have more minerals in it than what RO water should have? I'll be in a new town in about 6 weeks so I will see what results I get with different RO water. I will have a TDS meter by then.

 

[ajdelange]

More mineral (alkalinity) would produce a higher pH, not a lower one. Still mysterious.