More PH Measurement Question

[Duck&BarrelBrewing]

Hey all,

I have been scouring and trying to find this but I figured I would just throw it out there and see what I get in responses from people with way more brewing experience than me.

I am using a UniBrau System from Brau Built which is a BIAB system. When I measure the mash pH I am usually taking a measurement of the re-circulation mash wort. Now is this a good idea? I noticed that if I measure the pH of the recirculation mash wort vs a measurement of the wort that is in the kettle on top of the grist they are two different readings. Which way is best?

Then also when I make an acid addition, I tend to use Lactic Acid 88%, I notice that in both cases of measuring pH it takes a while for it to take effect. For the pH measurements , if I take multiple ones changes every time.

I guess what I am asking is what are some best practices of when and from where do you take pH measurements and how frequently?

I am allways feeling like I am in a rush to check pH and correct it. How crucial is it to check and/or correct pH as soon as possible in the mash so as to get the flavor profile you are wanting? Is there a time limit on how fast you need to correct a pH that is too high?

Thanks so much to anyone who replies. Just wanting to learn and learn the right way.

 

[kevin58]

I would forget about trying to correct Ph on the fly. Take a measurement about 15+ minutes into the mash... make your needed adjustments then in another 15 to 20 minutes later take another measurement. Note it and live with it. Use this info to better tweak your next batch.

 

[mac_1103]

It takes a while for mash pH to stabilize so there's not much point to measuring before about 10-15 minutes. And chasing pH during the mash is usually a losing game. Use a calculator to figure out how much acid to add at the start to hit your target pH. Check a few times during the mash. Take good notes and adjust the acid addition for the next brew.

 

[IslandLizard]

Measuring pH at any temperature other than within a few degrees around the calibration temp will give false readings. ATC (Automatic Temperature Correction) only works within a short range (+/- 10°F, or less) around the calibration temp.

Besides, most regular pH probes aren't designed to be used at much higher temps such as those encountered during the mash, and doing so will shorten their lifespan. So scoop out a representative sample from the mash with a metal cup and put it on ice for a minute (or 2) to get the sample to room temps. Then measure the pH.

And yes, as others have said, use a mash pH calculator. And make notes of differences between calculated and measured value(s) to hone in on more accurate predictions.

 

[Duck&BarrelBrewing]

Awesome! Thank you all for such great responses. I will definitely be doing this over the next few batches. I do have beer smith and I have used their calculator but it seems to add too much acid. However I was trying to adjust it on the fly and not give the 10-15min wait and also probably not letting it cool very much as well. I have recently purchased the kegland phone meter from more beer and I intend on trying to keep in temp specs and what not.

This is great advice. I will probably post here my results so that others with the same questions can see how these suggestions impact things.

Thanks again so much and I will post soon.

 

[hungupdown]

It takes a while for mash pH to stabilize so there's not much point to measuring before about 10-15 minutes. And chasing pH during the mash is usually a losing game. Use a calculator to figure out how much acid to add at the start to hit your target pH. Check a few times during the mash. Take good notes and adjust the acid addition for the next brew.

Agree. Use a calculator and take note of at least your final mash pH. Then use that measurement, to adjust acid additions of future brews.
Nowadays, I never normally need to measure mash pH.

But to use any calculator effectively you need to know your source water profile(s).

 

[pfabsits]

Measuring pH at any temperature other than within a few degrees around the calibration temp will give false readings. ATC (Automatic Temperature Correction) only works within a short range (+/- 10°F, or less) around the calibration temp.

Besides, most regular pH probes aren't designed to be used at much higher temps such as those encountered during the mash, and doing so will shorten their lifespan. So scoop out a representative sample from the mash with a metal cup and put it on ice for a minute (or 2) to get the sample to room temps. Then measure the pH.

And yes, as others have said, use a mash pH calculator. And make notes of differences between calculated and measured value(s) to hone in on more accurate predictions.

The ATC will work more than +/-10 oC. The influence of temperature is dependent on the isopotential point (pH 7). The further away the greater the impact. Attached is an article that was written a few years go that shows a graph of pH versus voltage response at different temperatures. The ATC portion of the meter reads the temperature and calculates what the value standardized to room temperature of 25 oC.

You are 100% right about temperature killing pH probes. The rule of thumb is that a pH electrode will last 1-2 years a for every 25 oC increase the life is cut in half. So at 50 oC (122 oF) the life is 6 months to 1 year. At 75 oC (165 oF) the life would be 3 to 6 months. It is best to cool a sample before using a pH meter.

The one thing to note is that after using is to clean the probe by rinsing with DI water then store in a storage solution. If you do not buy storage solution then use pH 4.0. It does not have the same salt concentration as a storage solution but at pH 4 any microbial growth is inhibited. Never store in DI/RO (purified water).

From my experience, it is difficult to achieve high accuracy. Most people can achieve 0.1 to 0.3 pH accuracy. To achieve better requires an understanding and ability to measure the offset and slope of the electrode and using fresh buffers.

 

[DuncB]

@Duck&BarrelBrewing
Just remember to look after your shiny new pH meter. The probe needs to be stored in the storage medium. Recalibrate when you haven't used it for a while and as mentioned cool your sample before taking a reading.
I have a freezer in my brewroom and just put a few mugs in the freezer and take one out and put the sample into this.
Don't use glass!!

 

[pfabsits]

@Duck&BarrelBrewing
Just remember to look after your shiny new pH meter. The probe needs to be stored in the storage medium. Recalibrate when you haven't used it for a while and as mentioned cool your sample before taking a reading.
I have a freezer in my brewroom and just put a few mugs in the freezer and take one out and put the sample into this.
Don't use glass!!

Yes, storage solution is the best. It is 3.5M KCl adjusted to pH 4 and has some microbial growth inhibitors. Need to keep stuff from growing on the pH sensitive glass. The reference portion of most pH electrodes is 3.5M KCl or 3.5M KCl saturated with AgCl. Storing in purified water will cause diffusion of the salt from inside the electrode to the outside (via junction) and the movement of water from outside to the inside by osmosis. Results in 3.5M KCl not being 3.5M anymore. That value is one of the nine mV potentials that make a pH measurement possible.

BTW since I work for Milwaukee Instruments I feel the need to mention that we have 15% off website orders through midnight Sunday.

 

[MaxStout]

BTW since I work for Milwaukee Instruments I feel the need to mention that we have 15% off website orders through midnight Sunday.

Welcome to HBT! Good to have another techie on board.

 

[ClaudiusB]

Measuring pH at any temperature other than within a few degrees around the calibration temp will give false readings. ATC (Automatic Temperature Correction) only works within a short range (+/- 10°F, or less) around the calibration temp.

Besides, most regular pH probes aren't designed to be used at much higher temps such as those encountered during the mash, and doing so will shorten their lifespan. So scoop out a representative sample from the mash with a metal cup and put it on ice for a minute (or 2) to get the sample to room temps. Then measure the pH.

And yes, as others have said, use a mash pH calculator. And make notes of differences between calculated and measured value(s) to hone in on more accurate predictions.

Calibration is best done when the buffer and the probe are at the same temperature based on the buffer's pH chart, no ATC is required. Meassuring the sample at the same temp as the calibration temp is also perfect, no ATC is required.

The pH probe response changes with temperature and the ATC must account for the change in the electrode response and be able to calculate the correct calibration-buffer pH value at the different calibration temperature.
After calibration I can measure at any temperature accurately with the help oft the ATC changing of the slope.
In my brewing process I do inline pH high temp measurements like manny plants in other industries.
ATC will not back calculate the pH value from the current process temperature down to the calibration temperature, pH of 5.35 @145°F will not be 5.35 @77°F.


Some info from one of my pH meters manufacturer, Hach.
The amount of change per unit pH is a function of temperature. This change in potential as a function of temperature. This change in potential as a function of temperature is linear as well.
At 20°C, the change in potential will be -58.17 mV per unit pH change, but at 30°C, the potential change will be -60.15 mV per unit pH change.
When a meter compensates for temperature during a pH measurement, this linear change of slope (the mV output per unit change in pH) is what the meter is compensating for).

A meter with fully automatic buffer recognition and temperature compensation will:

* determine the slope of the electrode from the standards used during the calibration at the temperature at which the calibration is conducted;
* and adjust the slope so that the pH response will be correct at any temperature during subsequent pH measurement.

 

[pfabsits]

Thanks! When it comes

Calibration is best done when the buffer and the probe are at the same temperature based on the buffer's pH chart, no ATC is required. Meassuring the sample at the same temp as the calibration temp is also perfect, no ATC is required.

The pH probe response changes with temperature and the ATC must account for the change in the electrode response and be able to calculate the correct calibration-buffer pH value at the different calibration temperature.
After calibration I can measure at any temperature accurately with the help oft the ATC changing of the slope.
In my brewing process I do inline pH high temp measurements like manny plants in other industries.
ATC will not back calculate the pH value from the current process temperature down to the calibration temperature, pH of 5.35 @145°F will not be 5.35 @77°F.


Some info from one of my pH meters manufacturer, Hach.
The amount of change per unit pH is a function of temperature. This change in potential as a function of temperature. This change in potential as a function of temperature is linear as well.
At 20°C, the change in potential will be -58.17 mV per unit pH change, but at 30°C, the potential change will be -60.15 mV per unit pH change.
When a meter compensates for temperature during a pH measurement, this linear change of slope (the mV output per unit change in pH) is what the meter is compensating for).

A meter with fully automatic buffer recognition and temperature compensation will:

* determine the slope of the electrode from the standards used during the calibration at the temperature at which the calibration is conducted;
* and adjust the slope so that the pH response will be correct at any temperature during subsequent pH measurement.

Very good information. The pH charts listed on the buffer bottles/sachets are useful to calibrate at a temperature that the instrument will be used at.

There have always been the argument that the actual pH of the solution is different at different temperatures. ATC corrects for the impact of temperature on the resistance of the glass (Nerstian slope response) but not the actual solution itself. There are a few process controllers that offer a solution temperature compensation adjustment. Similar to what is done with conductivity with its' temperature correction coefficient.

For the hobbyist that use common pH meters it is still important to cool the sample. The probes tend to use general purpose glass that is ideal for ambient temperatures. There is a high temperature formulation that is used for samples at elevated temperatures. The glass has a higher resistance to start with so as the temperature increases it approaches the resistance of general purpose.

I would be curious as to the difference that you see in the pH in the process from in-situ to cooled. I can only imagine the challenges that you face in maintenance. Not sure how often you do a process cal versus pulling/cleaning and then calibrating the process probe in buffers.

 

[Bassman2003]

If you are using the same input water you will find that pH will repeat itself. So a given grain bill with the same water will be pretty much the same pH every brew. Take the time to properly measure on each recipe you brew and once you have it dialed in, you will not have to measure much going forward.

The brewing world uses samples cooled to ~72-75F to discuss pH. I always encourage folks to do the same so all of our numbers line up. Cooled freezer or fridge water will lower a small mash sample fairly quickly. Get a stainless shot glass or measuring spoon that can be placed into a larger container of cooled water to chill. I purchased a SS set of three measuring cups at Wal-mart which works well. I put fridge water in the 1 cup measuring cup and hot wort in the tablespoon and clip the handles together. Works great.

As far as taking the wort out of the flow or at the top, I would think the flow would be fine.

Also, remember to only use fresh, in-date calibration solution. This stuff has about a year tops shelf life.

The guide for pH numbers is 5.4-5.6 for the mash and 5.1-5.3 at the end of the boil. This usually means you will add some more acid to the boil at 15 minutes to go (which helps Whirlfoc work better anyway).

 

[ClaudiusB]

Thanks! When it comes

Very good information. The pH charts listed on the buffer bottles/sachets are useful to calibrate at a temperature that the instrument will be used at.

There have always been the argument that the actual pH of the solution is different at different temperatures. ATC corrects for the impact of temperature on the resistance of the glass (Nerstian slope response) but not the actual solution itself. There are a few process controllers that offer a solution temperature compensation adjustment. Similar to what is done with conductivity with its' temperature correction coefficient.

For the hobbyist that use common pH meters it is still important to cool the sample. The probes tend to use general purpose glass that is ideal for ambient temperatures. There is a high temperature formulation that is used for samples at elevated temperatures. The glass has a higher resistance to start with so as the temperature increases it approaches the resistance of general purpose.

I would be curious as to the difference that you see in the pH in the process from in-situ to cooled. I can only imagine the challenges that you face in maintenance. Not sure how often you do a process cal versus pulling/cleaning and then calibrating the process probe in buffers.

All my samples taken during the brewing process are cooled to as close as possible to the calibration temperature for data recording.
Only one of my two process pH meters uses a high temperature probe all the other meters including the bench version have the general probes.
"There are a few process controllers that offer a solution temperature compensation adjustment." Only two of my meters have that function.
"I would be curious as to the difference that you see in the pH in the process from in-situ to cooled." Multiple water samples @145°F cooled to @77°F, pH changes 0.2-0.25. Wort, depending on grain composition has changed the pH from 145°F to 77°F by 0.3-0.35.
For reliable data I need to take a lot more samples and record the hot and cooled values .
"Not sure how often you do a process cal versus pulling/cleaning and then calibrating the process probe in buffers." always before the brewing process starts. My meters have a calibration reminder based on usage time.

 

[ClaudiusB]

@pfabsits what is your opinion abaut the ISFET Solid state probes? One of my meters supports them.

 

[pfabsits]

They are interesting. From talking with people at tradeshows they work well with semi-solids (i.e. soils, cheese). There was Sentron and IQ Scientific. I believe some of the major names in process (E&H, Knick) might be using them for food where glass is a big issue in continuous monitoring. They never gained acceptance for laboratory/Industrial use with bench and portables.

The glass pH electrode is based on the Nerstian response for a membrane potential. The glass bulb of a pH electrode is a membrane that follows that response. ISFET is a transistor based. They have to use an algorithm to mimic the Nerstian response.

Other than that I have not used them personally so I do not have first hand knowledge. Just what I was told from Product Managers at a couple of companies. IQ Scientific always had them on display in a container of lemonade. I tribute to Beckman who invented the pH meter for a friend, Glen Joseph, that had to measure the acidity of citric acid.

 

[ClaudiusB]

They are interesting. From talking with people at tradeshows they work well with semi-solids (i.e. soils, cheese). There was Sentron and IQ Scientific. I believe some of the major names in process (E&H, Knick) might be using them for food where glass is a big issue in continuous monitoring. They never gained acceptance for laboratory/Industrial use with bench and portables.

The glass pH electrode is based on the Nerstian response for a membrane potential. The glass bulb of a pH electrode is a membrane that follows that response. ISFET is a transistor based. They have to use an algorithm to mimic the Nerstian response.

Other than that I have not used them personally so I do not have first hand knowledge. Just what I was told from Product Managers at a couple of companies. IQ Scientific always had them on display in a container of lemonade. I tribute to Beckman who invented the pH meter for a friend, Glen Joseph, that had to measure the acidity of citric acid.

Thanks for your response.

 

[ClaudiusB]

@pfabsits a new one for you.
Why should a homebrewer purchase your pH meter model 102 when they can get an $8.00 pH strip with a display and the same specifications, according to the ads? PH strips with a display are my definition of those yellow sticks.

 

[Duck&BarrelBrewing]

@Duck&BarrelBrewing
Just remember to look after your shiny new pH meter. The probe needs to be stored in the storage medium. Recalibrate when you haven't used it for a while and as mentioned cool your sample before taking a reading.
I have a freezer in my brewroom and just put a few mugs in the freezer and take one out and put the sample into this.
Don't use glass!!

Ok, awesome thanks for the tips. I purchased storage solution and also cleaning solution for the probe to extend the life and accuracy as far as I can get