Is Mash Thickness Impacting pH predictions?

[Matozo]

I've been using Brun Water for some time, great tool. Some months ago I bought a pH meter (Hach Pocket Pro+) mainly for quick souring purposes, but also decided to take measurements during mash (room temperature, 15 minutes after dough in).

It was a big surprise when the predictions were quite off (actual measurements were almost always around ~0.2 higher than predicted).

After 2 batches of wrong predictions I decided to request a new water report (not the cheapest thing here in Brazil). The results were almost identical to the previous one.

I revisited every field of the spreadsheet and typed the updated values.

The next brew same thing happened: wrong pH prediction (Brun Water ~0.2 lower than actual).

I'm trying to track down what could be the culprit here. I'm a full volume BIAB brewer that brews almost always under 1.060 OG, so my mash thickness is quite high.

My water is high in alkalinity too.

Here is the water report input from my spreadsheet:

Any help is appreciated.
Cheers.

 

[Silver_Is_Money]

There is no need to get caught in the trap of implicitly assuming that software must in all cases be right and thereby your careful and repeated pH measurements are somehow to be assumed in error. Software is merely making multitudes of educated guesses (assumptions) based upon its programmers chosen algorithms (math models) treatment of the highly limited data that you feed into it. These limitations with regard to the data input are particularly significant with respect to the malts which comprise your grist bill, whereby you only provide their weight, "nominal" color, and "nominal" class status for each entry. You on the other hand are making repeated hard and factual "real world" measurements. Trust your measurements.

 

[Big Monk]

I've been using Brun Water for some time, great tool. Some months ago I bought a pH meter (Hach Pocket Pro+) mainly for quick souring purposes, but also decided to take measurements during mash (room temperature, 15 minutes after dough in).

It was a big surprise when the predictions were quite off (actual measurements were almost always around ~0.2 higher than predicted).

After 2 batches of wrong predictions I decided to request a new water report (not the cheapest thing here in Brazil). The results were almost identical to the previous one.

I revisited every field of the spreadsheet and typed the updated values.

The next brew same thing happened: wrong pH prediction (Brun Water ~0.2 lower than actual).

I'm trying to track down what could be the culprit here. I'm a full volume BIAB brewer that brews almost always under 1.060 OG, so my mash thickness is quite high.

My water is high in alkalinity too.

Here is the water report input from my spreadsheet:

Any help is appreciated.
Cheers.

Remember that BW (and water chemistry sheet for that matter) is giving you an estimate. Even the best estimates are wrong sometimes. Conversely, meters are wrong sometimes as well.

What Base malt did you use? Is you scale accurate?

Right now you are doing exactly what Martin advocates: trust but verify! Always check he sheet against a meter.

Are you sure your meter is being calibrated properly? Are you doing it before every brew session?

 

[Matozo]

I completely agree.

What really bothers me is that most brewers (including some I really respect) say that BW nails pH every single time (maybe a difference in the hundreds).

That makes me feel like I'm doing something wrong or the spreadsheet doesn't work that well with my current setup and water.

My guess is that it has something to do with mash thickness and/or my high alkalinity water.

I don't know many people that are using BW with high carbonate water content but every other ion in low concentration.

I want to believe that my water is different and not so friendly with BW.

Anyway, I talked to a comercial brewery that also uses municipal water here and they said they 'cheat' by manipulating the alkalinity of the water report tab in order to achieve a more accurate pH prediction.

I take volumes and weight very seriously. My pH meter gets calibrated before every brew session.

Usually my base malts are: Brazilian Agrária Pils, Bestmalz or Weyermann Pils, and Château or Bestmalz Pale (US malts here are rare).

 

[Silver_Is_Money]

The DI mash pH's of your various locally available Pilsner malts are likely somewhere around 5.8 to perhaps 5.9 (with 6.0 not being totally out of the question). It is highly possible that the spreadsheet you reference is incapable of making the correct assumption that the initial pH of this type of malt is that high. If that is the case, then it would account for at least a fair percentage of the mash pH deviation you are witnessing.

 

[Matozo]

The DI mash pH's of your various locally available Pilsner malts are likely somewhere around 5.8 to perhaps 5.9 (with 6.0 not being totally out of the question). It is highly possible that the spreadsheet you reference is incapable of making the correct assumption that the initial pH of this type of malt is that high. If that is the case, then it would account for at least a fair percentage of the mash pH deviation you are witnessing.

Definitely something to keep in mind. Thanks!

This weekend I'll be brewing a fest bier with German malts (Best malz Pils is 70% of the grain bill).

 

[Silver_Is_Money]

Another thing to consider is that the spreadsheet you reference may potentially be over-assuming the downward shift of mash pH due to added Ca and Mg. We know now that Kolbach measured the impact of mineralization upon pH well downstream at "kettle knock-out", and not during the mash, let alone early in the mash. Knock-out pH is generally a few tenths lower than mash pH.

 

[Big Monk]

The DI mash pH's of your various locally available Pilsner malts are likely somewhere around 5.8 to perhaps 5.9 (with 6.0 not being totally out of the question). It is highly possible that the spreadsheet you reference is incapable of making the correct assumption that the initial pH of this type of malt is that high. If that is the case, then it would account for at least a fair percentage of the mash pH deviation you are witnessing.

This is a big one. Especially when using Weyermann base malts. They are consistently between 5.8-6.0 for the MA sheet DI pH. I get around this in my sheet because base malts (except for Munich) don't get a color based acidity calculation but rather a user input for DI pH.

An easy hack for BW would be to document what the pH difference was from estimate to actual and then change the color for that base malt until the values match. Then just use that color for that base malt in the future and your estimates should be bang-on to the measurements with your meter.

That is an old trick proposed a long time ago by Martin.

 

[Oginme]

Any water spreadsheet for brewing is subject to the assumptions made when doing the calculations. As Silver Is Money pointed out there can be very substantial differences between malts and maltsters. The variety of barley, the geographic region it is grown, how it is handled and stored before and after malting can all play a role in the contribution towards pH. Then you have the different maltings. The spreadsheets tend to group the malts together, but a pale 2-row malt at 2L color and Pale Ale malt at 3.5L color will have different contributions. Likewise with roasted malts which cover a vast range of colors and malting procedures.

If you find the software continually predicts low, then take that into account and set your target pH higher and work off of that.

 

[TheHopfather]

Brun Water predictions are usually about 0.2pH lower then my actual measurements. Over a number of batches you can figure out if this is consistent or not and just adjust from there. I just note the difference and plan for a pH that will be ~0.2pH higher then Brun Water predicts.

 

[ScrewyBrewer]

When my mash actual pH measurements are within ~0.2 higher or lower than predicted I pat myself on the back and pour a pint. There are so many other variables involved when predicting pH. Things like DI pH of the actual grain bill, moisture content of calcium chloride additions and software rounding errors, just to name the more obvious. They all play a role in pH prediction 'accuracy'.

 

[IslandLizard]

[...] I'm trying to track down what could be the culprit here. I'm a full volume BIAB brewer that brews almost always under 1.060 OG, so my mash thickness is quite high. [...]

That's either an incorrect assessment or a typo.
Your mash thickness is actually quite low, since you use all your water in the mash at once, without any sparging. IOW, your mash is thin! Together with the high water alkalinity, there's lot to compensate. Do you happen to know if that alkalinity fluctuates much or if it is at least stable? A water test is no more than a single snapshot, only good if things remain stable.

Have you tried the "Mash Made Easy" calculator and compare the results?

 

[Dustin_J]

woops - just noticed you were measuring at room temp. Disregard my comment.

 

[Matozo]

Another thing to consider is that the spreadsheet you reference may potentially be over-assuming the downward shift of mash pH due to added Ca and Mg. We know now that Kolbach measured the impact of mineralization upon pH well downstream at "kettle knock-out", and not during the mash, let alone early in the mash. Knock-out pH is generally a few tenths lower than mash pH.

That's also interesting since I was always adding Ca and Mg (Mg from Epsom Salt for Sulfate adjustments since finding food grade Gypsum was impossible). Right now I have access to Gypsum (bought the analytical grade anyway).

This is a big one. Especially when using Weyermann base malts. They are consistently between 5.8-6.0 for the MA sheet DI pH. I get around this in my sheet because base malts (except for Munich) don't get a color based acidity calculation but rather a user input for DI pH.

An easy hack for BW would be to document what the pH difference was from estimate to actual and then change the color for that base malt until the values match. Then just use that color for that base malt in the future and your estimates should be bang-on to the measurements with your meter.

That is an old trick proposed a long time ago by Martin.

Great tip! Never thought of doing that (I was more towards the hack on the water report tab). Thanks!

When my mash actual pH measurements are within ~0.2 higher or lower than predicted I pat myself on the back and pour a pint. There are so many other variables involved when predicting pH. Things like DI pH of the actual grain bill, moisture content of calcium chloride additions and software rounding errors, just to name the more obvious. They all play a role in pH prediction 'accuracy'.

Yeah, I agree. But I would sleep better with a more accurate estimate from BW.

I recently read a Scott Janish article on finished mineral content that made me less worried with small differences.

Not to mention Brulosophy experiments on mash pH.

That's either an incorrect assessment or a typo.
Your mash thickness is actually quite low, since you use all your water in the mash at once, without any sparging. IOW, your mash is thin! Together with the high water alkalinity, there's lot to compensate. Do you happen to know if that alkalinity fluctuates much or if it is at least stable? A water test is no more than a single snapshot, only good if things remain stable.

Have you tried the "Mash Made Easy" calculator and compare the results?

You're totally right, my mistake. I meant low mash thickness!

Unless when things go crazy (lots of rain, specially in the first months of the year) or when there's a network maintenance my water supply is pretty stable (totally anecdotal, but that's been my experience so far).

Never heard of Mash Made Easy, thanks for sharing. I'll check that out.