Predicting pH with Brun Water

I've been using Brun for a while now and for most of my IPAs and dark beers, I get pretty close, probably with in .1 or .2 for mash pH reading compared to predicted.

But on some beers, usually with out any large crystal or roast additions, the pH prediction is much further off.

Here is my latest example.

Using 100% RO water, 10.4 Gallons for a 6 gallon batch, no sparge

Grist:
Brun' estimates 5.5 mash pH (room temp).

I doughed in at 153 and hit strike temp of 148F and stir in the mineral additions. I wait about 8 minutes, do a bit of recirculation to mix things some more and then I pull a sample into a chilled cup.

I calibrate my pH meters (HMDPH200 and no-brand from AHS) ( prior to reading (7 and 4 solution)

On the above mash, I measured 5.12 at about 90F. I added 1.0g of Baking Soda and after another 5 minutes, this was up to 5.21 at 100F, and then another 1.6g of Baking Soda, and brought me up to 5.42 at 97F.

I'm wondering if this is the typical for the 'ball park' estimate of spreadsheet calculations or if I'm missing something in my process or input.

btw, if I add the 2.6g of Baking soda back to Brun, it calculates a pH of 5.7, so still a good .3 pH off from what I measure.

Thoughts?

Thanks for your time, and the spreadsheet!

Try this and see if it is any closer.
http://www.brewersfriend.com/mash-chemistry-and-brewing-water-calculator/

Never hurts to get a second opinion.

Hermit said:

Try this and see if it is any closer.
http://www.brewersfriend.com/mash-chemistry-and-brewing-water-calculator/

Never hurts to get a second opinion.

Click to expand...

Thanks.

A quick run through that using 13 GH value (assuming 95% removal of hardness of local water) and the rest of my inputs, nets a mash pH of 5.2 -- which was much closer to actual (5.12). Adding in the 2.6g of baking soda also came closer to my last measurement, BF calculator predicts 5.3, my reading was 5.36/5.4.

I'll keep playing with both of these. I may just need to adjust the mineral content of the RO water until the pH matches (or I can send off a sample).

ne0t0ky0 said:

Thanks.

A quick run through that using 13 GH value (assuming 95% removal of hardness of local water) and the rest of my inputs, nets a mash pH of 5.2 -- which was much closer to actual (5.12). Adding in the 2.6g of baking soda also came closer to my last measurement, BF calculator predicts 5.3, my reading was 5.36/5.4.

I'll keep playing with both of these. I may just need to adjust the mineral content of the RO water until the pH matches (or I can send off a sample).

Click to expand...

Someone posted a test on their RO water recently and rejection rates weren't the same for all compounds. I was using an aquarium test and it gave reasonable results but I finally found a water report on line and it was for 2011 "typical" values but when I plugged them in for my last brew the mash calculation was about .03 off. I can live with that given I am new to the pH meter so there will be some error in that also.

Hmm? I had not used Kai's calculator before. But I input the values above and produced a nearly identical mash pH prediction of 5.6 with that model. The ion concentrations were identical for the water after the mineral additions. Sorry, no cigar, neither model is better in this case.

The problem with the calculators for this case is the extremely thin water to grist ratio. It appears that is the likely cause of the discrepancy. I guess I've never experimented with mashes as thin as this. I'd suggest that the OP send the calculated predictions and observed results to me for analysis.

One problem is the pH measurements were a little warm, but that should only mean a tenth or so higher for the observed results.

Very curious.

mabrungard said:

Hmm? I had not used Kai's calculator before. But I input the values above and produced a nearly identical mash pH prediction of 5.6 with that model. The ion concentrations were identical for the water after the mineral additions. Sorry, no cigar, neither model is better in this case.

The problem with the calculators for this case is the extremely thin water to grist ratio. It appears that is the likely cause of the discrepancy. I guess I've never experimented with mashes as thin as this. I'd suggest that the OP send the calculated predictions and observed results to me for analysis.

One problem is the pH measurements were a little warm, but that should only mean a tenth or so higher for the observed results.

Very curious.

Click to expand...

Ill get the spreadsheet to you in a bit. I did play with the total volume by a few gallons, 8 or 9 gallons or 11 and it didn't affect the pH by more than .1 pH...

The thin mash is typical for Biab, and I use this mash method almost exclusively. It'll be very cool to be able to dial the spreadsheet calculatation in for this type of mash.

mabrungard said:

One problem is the pH measurements were a little warm, but that should only mean a tenth or so higher for the observed results.

Click to expand...

Shouldn't the meter be correcting for this?

ne0t0ky0 said:

Shouldn't the meter be correcting for this?

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I think the temperature compensation is for telling when the sample is different temperature than the temperature of the calibration solution. This threw me a little too at first. In the sample it is going to tell you what the pH is at that moment. It doesn't spit it out what it would be at a specific temperature.

Hermit said:

I think the temperature compensation is for telling when the sample is different temperature than the temperature of the calibration solution. This threw me a little too at first. In the sample it is going to tell you what the pH is at that moment. It doesn't spit it out what it would be at a specific temperature.

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Hrm, and of course we are expecting a pH shift based on temperature anyhow... (room temp of 5.5ish for a mash temp pH of 5.2ish) ... it must change based on temp.

So, what temp do folks normally do the reading at? My room temp calibration solution is around 74F ... should I have cooled my sample down to 74F? As you can see, I've been going with close to 90F as my normal temp reading.

Reading a few other threads, it looks like I should be cooling to 25C/77F to match the calibration solution temps.

I also found a pH / temp adjustment calculator and ran through the numbers I posted

5.12 pH @ 90F corrected is: 5.0793
5.21 ph @ 100F corrected is: 5.1414
5.42 pH @ 97F corrected is: 5.3673

ne0t0ky0 said:

The thin mash is typical for Biab, and I use this mash method almost exclusively. It'll be very cool to be able to dial the spreadsheet calculatation in for this type of mash.

Click to expand...

I know from playing with BW's mash pH prediction that it doesn't account for mash thickness. That should be a problem with BIAB. But in this cases mash thickness won't matter since the residual alkalinity is close to 0.


But I'm also puzzled about the low mash pH that you observed.

Kai

ne0t0ky0 said:

5.12 pH @ 90F corrected is: 5.0793
5.21 ph @ 100F corrected is: 5.1414
5.42 pH @ 97F corrected is: 5.3673

Click to expand...

Where did you find this and what is the temp of the correction?

Kai

Kaiser said:

Where did you find this and what is the temp of the correction?

Kai

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http://www.hamzasreef.com/Contents/Calculators/PhTempCorrection.php

And I assume 25C, as if I put that temp in the calculation, it results in the same reading as the input.

ne0t0ky0 said:

http://www.hamzasreef.com/Contents/Calculators/PhTempCorrection.php

And I assume 25C, as if I put that temp in the calculation, it results in the same reading as the input.

Click to expand...

Thanks.

This doesn't apply here. The calculator calculates the temperature depended shift in the probe's response to a given pH. It's the TC function (temperature correction) of a meter that has ATC (Automatic Temperature Correction). The temp dependent pH shift in wort (or any other substance for that matter) is different. It is an actual change in pH and the reason why we want to settle on one temp for pH measurements. I like 25 C since that's the temp at which my calibration buffers are correct.

Kai

Kaiser said:

Thanks.

This doesn't apply here. The calculator calculates the temperature depended shift in the probe's response to a given pH. It's the TC function (temperature correction) of a meter that has ATC (Automatic Temperature Correction). The temp dependent pH shift in wort (or any other substance for that matter) is different. It is an actual change in pH and the reason why we want to settle on one temp for pH measurements.

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Interesting. Could such a correction table be created for wort? or would it not be feasible given all of the variability of the mash composition?

Kaiser said:

I like 25 C since that's the temp at which my calibration buffers are correct.

Kai

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Good to know; it's never been clear to me until now that I need to select a target room temperature and use that consistently with the pH measurements.

Thanks!

ne0t0ky0 said:

Good to know; it's never been clear to me until now that I need to select a target room temperature and use that consistently with the pH measurements.

Thanks!

Click to expand...

I seem to remember a private conversation via PM with AJ a while back and this was the issue I remember. Just way too many variables in differing worts.

ne0t0ky0 said:

Good to know; it's never been clear to me until now that I need to select a target room temperature and use that consistently with the pH measurements.

Thanks!

Click to expand...

Just to point out; this is my failure to comprehend what's written quite clearly in the pH Meter Calibratation thread

2. Cool the sample to room temperature, ideally the same temperature as the buffers you used for calibration. This prolongs electrode life and reduces the burden on ATC. If you use a small metal saucepan you can achieve the cooling quickly by immersing it in cool/cold water.

Click to expand...

ne0t0ky0 said:

Interesting. Could such a correction table be created for wort? or would it not be feasible given all of the variability of the mash composition?

Click to expand...

maybe. Someone would have to be willing to subject his/her pH meter probe to high mash temperatures for many different mashes to see what the correlations is and what the variability is.

Kai

Kaiser said:

maybe. Someone would have to be willing to subject his/her pH meter probe to high mash temperatures for many different mashes to see what the correlations is and what the variability is.

Kai

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I'd say go low first and see if a curve developed and then go up.

I experienced a lower mash pH recently on a recipe with some carafa and crystal malts. I mixed both baking soda and pickling lime in my mashing liquor to raise alkalinity, and also add some sodium, aside from other additions.

The model was fine at 1.2 qt/lbs for the protein rest, but the second infusion to saccharification lead to a lower pH of 5.1. It took a surprising amount of pickling lime to raise to my desired 5.4 pH The water/grist ratio was about 1.8 qt/lbs.

I forgot to note how much pickling lime I added. I normally measure to 0.1 g, but I was hasty to raise my mash pH. In the future, though, I will ensure I have extra lime on hand during mash-in. I'd rather add lime (raise alkalinity, and add calcium), than lower pH with an acid and leave the corresponding anions. Not after all the hassle of RO filtering!

lockwom said:

I experienced a lower mash pH recently on a recipe with some carafa and crystal malts. I mixed both baking soda and pickling lime in my mashing liquor to raise alkalinity, and also add some sodium, aside from other additions.

The model was fine at 1.2 qt/lbs for the protein rest, but the second infusion to saccharification lead to a lower pH of 5.1. It took a surprising amount of pickling lime to raise to my desired 5.4 pH The water/grist ratio was about 1.8 qt/lbs.

Click to expand...

If I'm reading this correctly you struck at protein rest temperature and found the pH OK (which I presume means around 5.4), then infused to step to saccharifcation and found the pH had fallen back to 5.1? Is that correct?

If I am reading that right then something is wrong. It is normal for pH to drift but the rate usually slows dramatically after 15 minutes or so unless you are doing decoctions and even then it isn't likely to be much unless the water is calcium rich. And the drift is usually upward. So if you see a drop of 0.2 - 0.3 after an infusion I'd check the meter. Inexpensive meters drift quite a bit. There is a Sticky here that goes into how to check the stability of your meter.

I double-checked with color pHast strips. Not the most reliable, but they validated my measurement when accounting for bias.

The water had plenty of calcium. And I did make measurements within the unstable period you mentioned.

BW estimated my protein rest pH to be 5.3 (fine for proteolytic enzyme range) and mash pH as 5.5.

I could have:
- mismeasured salts
- faulty protein rest pH measurement
- bad sensor

I don't have enough recorded data to challenge the model, nor enough evidence that it was not my fault. But I just wanted to mention the worthiness of having lime on hand, since properly estimating pH for the different malts is hard.

My original suspicion was that the model underestimated the crystal contribution.

I haven't seen crystal malts that contribute more acidity than what the model predicts, but I have seen base malts that contribute more acidity than expected. Rahr malts seem to have this tendency. I assume they slightly acidify their malts and most brewers appreciate that since many have excess alkalinity they have to deal with.

Since this was a No-Sparge brewing case, I would have assumed that the pH value would have biased a little high and not low. I'm still scratching my head on this one.

lockwom said:

The water had plenty of calcium. And I did make measurements within the unstable period you mentioned.

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What was the calcium content and/or RA of the water you added?

Kai

mabrungard said:

I Rahr malts seem to have this tendency. I assume they slightly acidify their malts and most brewers appreciate that since many have excess alkalinity they have to deal with.

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I have wondered if they have a specific large client that they cater to in this regard.

Kaiser said:

What was the calcium content and/or RA of the water you added?

Kai

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Calcium was 51 ppm, and Mg was 5 ppm. I calculate the water had RA of -6, seemed fine for an ambery beer.

Here is what I suspect went wrong: I added the pickling lime for that batch to the mash liquor before heating it. I'm sure it was readily dissolved, but perhaps some of the pickling lime content precipitated when heated combined with some calcium content (that is, not sure it was HCO3 at the higher grain-less pH, but I still bet it it left the solution).

I've since added pickling lime to a batch with acidic grains directly after adding grains with very reliable results. But I'm not ruling out some form of mismeasurement. I'm planning on brewing a porter tomorrow, so I will try to verify my process. How long should I wait to measure pH after adding the pickling lime?

Does my explanation above sound plausible?

(Also, there was some Rahr 2-row and Weyermann Munich I in there, it could have had more acid than the "Base Malt" model in BrunWater). This year, I bought CMC 2-row to see how it compares to last year's Rahr.

Even with 0.6 lbs of roasted malts, Kai and Martin's spreadsheets predicted the mash pH. Lesson learned, add the pickling lime to the mash after adding the grains.