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-   -   Predicting pH with Brun Water (http://www.homebrewtalk.com/f128/predicting-ph-brun-water-387040/)

ne0t0ky0 02-03-2013 07:51 PM

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:
Code:

GW 2 row    (B) 3.0#    2L
Pale Malt  (B) 2.0#    3L
Pilsner    (B) 4.0#    2L
White Wheat (B) 2.0#    2.4L
Caramunich  (C) 3.0#    51L

14# total.

I'm adding in:

Gypsum (CaSO4)              5.7g
Calcium Chloride (CaCl2)    2.5g
Pickling Lime (Ca(OH)2)    1.6g

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!

Hermit 02-03-2013 08:16 PM

Try this and see if it is any closer.
http://www.brewersfriend.com/mash-ch...er-calculator/

Never hurts to get a second opinion.

ne0t0ky0 02-03-2013 08:37 PM

Quote:

Originally Posted by Hermit (Post 4860637)
Try this and see if it is any closer.
http://www.brewersfriend.com/mash-ch...er-calculator/

Never hurts to get a second opinion.

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).

Hermit 02-03-2013 08:51 PM

Quote:

Originally Posted by ne0t0ky0 (Post 4860697)
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).

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.

mabrungard 02-03-2013 09:33 PM

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.

ne0t0ky0 02-03-2013 09:51 PM

Quote:

Originally Posted by mabrungard (Post 4860850)
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.

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.

ne0t0ky0 02-03-2013 10:52 PM

Quote:

Originally Posted by mabrungard (Post 4860850)
One problem is the pH measurements were a little warm, but that should only mean a tenth or so higher for the observed results.

Shouldn't the meter be correcting for this?

Hermit 02-03-2013 11:09 PM

Quote:

Originally Posted by ne0t0ky0 (Post 4861087)
Shouldn't the meter be correcting for this?

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.

ne0t0ky0 02-03-2013 11:43 PM

Quote:

Originally Posted by Hermit (Post 4861131)
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.

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

Kaiser 02-04-2013 12:21 AM

Quote:

Originally Posted by ne0t0ky0 (Post 4860920)
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.

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


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