[rbowers]

I have been trying to dial in water chemistry a bit more accurately and have gotten some conflicting results from brewing calculators.  I have been using Bru'nWater the last several batches and it seems to over estimate the addition of acid (at least in the last batch).  I have looked around at other calculators and the same data entry seems to yield different results.  I have a water test kit and have gotten the following results

Base Water:
Ca++ 4
Mg++ 0
Na++ 20
SO4 0
Cl- 10
Bicarbonate 48
pH 7.13

Brewing tomorrow and have the following grist and goal water profile:
Grist:
25lb Vienna
0.75lb Spec B
0.5lb Chocolate
0.5lb Carafa II
0.25lb Roasted Barley

Water Goal Profile:
Ca:61
Mg:9
Na:20
SO4:80
Cl:78
Bicarb:48

10gal mash water ~1.5qrt/lb.

I guess my question is why is one calculator generating a mash pH with no acid additions of 5.28 and another says it will be 5.53?  I guess it is not a terribly big deal as both are in a decently acceptable range.  Last brew day though I went with the first one, added the recommended acid additions and ended up with a pH of 4.9.  Just trying to get a feel for which one to trust.  Does anyone have any logic to suggest one more accurate than the other?

[Robert]

When are you pulling your samples for pH measurement?  I thought, at first, that Bru'n Water was overestimating acid, as it was predicting >5.4 and I was getting <5.3. But I was checking pH right at mash in.  I found that if I wait 15 minutes, the pH has settled in, and Bru'n Water is dead on every time and the pH locks in right through the mash, sparge and boil.

[rbowers]

Probably 5-10 min in.  I feel like I have had mixed results with Brun'water.  One batch I felt the acid addition "seemed" excessive so I cut it back and low and behold I came in high.  The next batch I trust it, add the full amount, and bottom out around 4.9.  Makes me think something is wrong with my process or calculations but I perplexed why different calculators give different #s with the same entry data.  Guess I will keep playing around with it, take some good notes, and see what happens.

[braufessor]

Are you sure you have the grain bill entered correctly, roast malts selected as "roast" and not "base", correct lovibonds entered, correct volumes of mash, sparge, etc...  I have missed something like that in B'run water and it will throw it off.  That is always my first thought when something does not make sense.

[BitterItDown]

Makes me think something is wrong with my process or calculations but I perplexed why different calculators give different #s with the same entry data.

Those spreadsheet calculators operate off of equations that have been fitted to data points collected from various malt samples.  The thing is some of these data points are outliers and don't fit well within the fitted equations, also each malt and worse yet, each batch is different.  BruNwater most likely has three equations fitted to samples of base, crystal and roast malts.  Try setting a base malt as a roast malt and look at the effect it has on the predicted pH.

Other calculators like "Mash Made Easy" allow you to enter what is known as the DI pH of each malt.  The DI pH is the pH of a mash made with distilled water and a small amount of a finely ground malt sample.

There is no spreadsheet or set of equations that can fully and accurately predict mash pH, though most do a good approximation.  (Of course these spreadsheets *have* done a great service to the homebrew world.)

Certainly data entry errors, measurement errors, accuracy errors and repeatability errors, etc.. all accumulate and affect the outcome.

The best way to determine mash pH is to conduct a test mash.  This is a very small proportinally scaled down mash made of the same malts as the original recipe.  From this one can determine what has to be done, if anything, to correct the pH.

If you'd like to read more about how the spreadsheets work:

Kai's paper:

http://braukaiser.com/documents/effect_of_water_and_grist_on_mash_pH.pdf

AJ Delanges papers:

http://www.wetnewf.org/untitled.html

[denny]

Probably 5-10 min in.  I feel like I have had mixed results with Brun'water.  One batch I felt the acid addition "seemed" excessive so I cut it back and low and behold I came in high.  The next batch I trust it, add the full amount, and bottom out around 4.9.  Makes me think something is wrong with my process or calculations but I perplexed why different calculators give different #s with the same entry data.  Guess I will keep playing around with it, take some good notes, and see what happens.

Wait a while.  Martin has said that even if the pH seems high or low at the beginning, it gravitates toward 5.4 ash the mash progresses.

[Robert]

In Re: BitterItDown's reply #4:  I used to do little test mashes in a saucepan for every new recipe,  new malt, water profile, etc.  I find Bru'n Water so close (closer than all the opportunities for error in that process) that I now trust it for the first full batch.  It's unlikely you'll need to make more than tiny tweaks from there.

[Big Monk]

Probably 5-10 min in.  I feel like I have had mixed results with Brun'water.  One batch I felt the acid addition "seemed" excessive so I cut it back and low and behold I came in high.  The next batch I trust it, add the full amount, and bottom out around 4.9.  Makes me think something is wrong with my process or calculations but I perplexed why different calculators give different #s with the same entry data.  Guess I will keep playing around with it, take some good notes, and see what happens.

Wait a while.  Martin has said that even if the pH seems high or low at the beginning, it gravitates toward 5.4 ash the mash progresses.

One point to note here: You have to be in the ballpark using estimation first. A very low or very high pH won’t just magically gravitate to 5.4.

Not a dig at your comment, just more of a caveat.

[mabrungard]

One point to note here: You have to be in the ballpark using estimation first. A very low or very high pH won’t just magically gravitate to 5.4.

Very true!! That phenomena only seems to work when I've done treatment measures that were targeted to fall in the 5.2 to 5.6 range. Now if I could only figure out why that phenomena occurs???

[Big Monk]

One point to note here: You have to be in the ballpark using estimation first. A very low or very high pH won’t just magically gravitate to 5.4.

Very true!! That phenomena only seems to work when I've done treatment measures that were targeted to fall in the 5.2 to 5.6 range. Now if I could only figure out why that phenomena occurs???

Well, is there a relation to the amount of conversion to the acidity potential of the grains?

[BitterItDown]

One point to note here: You have to be in the ballpark using estimation first. A very low or very high pH won’t just magically gravitate to 5.4.

Very true!! That phenomena only seems to work when I've done treatment measures that were targeted to fall in the 5.2 to 5.6 range. Now if I could only figure out why that phenomena occurs???

Well, is there a relation to the amount of conversion to the acidity potential of the grains?

AJ and Martin discuss this phenomenon here:

https://www.homebrewtalk.com/forum/threads/mash-ph-too-low.575685/

[Robert]

One point to note here: You have to be in the ballpark using estimation first. A very low or very high pH won’t just magically gravitate to 5.4.

Very true!! That phenomena only seems to work when I've done treatment measures that were targeted to fall in the 5.2 to 5.6 range. Now if I could only figure out why that phenomena occurs???

Well, is there a relation to the amount of conversion to the acidity potential of the grains?

AJ and Martin discuss this phenomenon here:

https://www.homebrewtalk.com/forum/threads/mash-ph-too-low.575685/

Thanks for the link.  Within the limits of my understanding, that explains what I've experienced:  malt and liquor constitute a system that, once you set it up, will do what it will do; once the system is in place it is difficult to pull it away one way or the other. Maybe Martin finds mashes gravitate toward 5.4 because he has (as we would expect, effectively) set the conditions for that;  were he to erroneously set up the conditions for 5.0 or 6.0, that would be the center of gravity.  It jibes with my experience that trying to adjust pH with acids or bases after mashing-in is futile.  Just take notes and treat your water differently next time.  The takeaway here is probably:  wait 15 minutes into the mash to test pH,  and then live with it.  Bru'n Water will probably have got you what you need, or close enough.

[mabrungard]

Maybe Martin finds mashes gravitate toward 5.4 because he has (as we would expect, effectively) set the conditions for that;  were he to erroneously set up the conditions for 5.0 or 6.0, that would be the center of gravity. 

Well, I'm not sure that this is true. I do try and target pH's several tenths above and below that 5.4 median (dependent upon style brewed), and that tendency for the pH to trend toward 5.4 is ever present. Now, I haven't tried targeting the large deviations mentioned above, but its an interesting experiment. Now if I only had the time to experiment.

[rbowers]

Well it went ok yesterday.  I mashed in and waited a bit longer before drawing a sample (~12-15min).  A predicated pH of 5.31 (Brun Water) came in at 5.24 (which I am totally ok with). I did not add any acid this go round and the malt bill had approximately 6% roast category grains.  In terms of predicting what things will do the next time around I guess I am still at a loss.  I think I am correct in my thought that pH is a log function and so I can't just adjust things in Brun'Water and always expect the pH to be off 0.07 points.  However, given the narrow range of pH in brewing we are looking for perhaps it is a decent place to start.  I guess I will just take more notes as I go over the next few batches.  Thanks for the info.

[BitterItDown]

I think I am correct in my thought that pH is a log function and so I can't just adjust things in Brun'Water and always expect the pH to be off 0.07 points.

Not quite the way it works, reference my earlier post.

These types of spreadsheets are precise, in that they'll return the same values for the same inputs but the accuracy (estimated pH vs. actual pH) will vary from batch to batch.