ph meter question

[IchLiebeBier]

All,
I've been brewing with EZ water calculations for a while, and they have always been spot on as measured with my ph meter. But yesterday, I brewed an all-grain RIS and the mash ph kept reading lower than expected, and a bit inconsistent (calibrated milwaukee ph58 dipped directly into the mash).

So my question is this: since the ph meter measures electrical potential in the solution, would the suspension of the grain in a heavier mash affect the result? In a normal brew, after stirring the mash, the grain settles a bit and leaves a layer of wort deep enough to measure. But with the RIS, it didn't, and the measured spot was pretty thick with grain.

Thanks.

 

[mabrungard]

If you were dipping your pH probe into hot wort, you weren't reading the correct pH. In addition, you have probably shortened the life of the meter. The presence of grain has very little to do with pH, since its the liquid that carries the ionic content and registers the pH.

 

[dmcman73]

The ATC correction in most pH meters is only good up to about 110-120 degrees. If you measured the pH directly into your mash, chances are you where measuring at 150-155 degrees which will affect the pH measurement. Your best way to measure the pH (and it's the way I do it) is draw off a sample of wort from the mash tun's drain valve into a small measure cup, cool the wort down (i cool it down to about 80 degrees or so buy placing the glass measure cup into ice cold water or ice cubes and stir it until it cools, take a minute since you only need enough wort yo submerge the probe into. Once it's cooled, then measure the pH.

Also, different grains affect your water pH differently then others.

 

[IchLiebeBier]

Thanks for the responses. I don't know where I heard you could just put it in the mash. I thought I read it somewhere.

 

[mabrungard]

ATC has usefulness in only a minor temperature range, near room temperature. As the temperature of wort increases, not only does the measurement ability of the probe change (which ATC corrects for), the actual pH of the wort changes too (which ATC does not correct for). So you are kidding yourself in assuming that ATC does any good in the brewery. Cooling your wort to near room temp and allowing the meter's ATC to correct for the minor temperature effects, is the way to measure pH in the brewery. The side effect is that your probe will last longer too.

 

[kombat]

Do you guys regularly/ever calibrate your pH meters?

 

[Dolomieu]

For an accurate reading, pH meters should be calibrated each day you plan on using it. If you read a laboratory SOP it will most likely state that the meter will be calibrated prior to use (morning) and then again mid day(3-4 hours post calibration). I'm sure this is over kill for a brew day but if you are using it with out calibrating it first, you might as well leave it on the shelf.

 

[kombat]

Do you just calibrate it with distilled water (pH = 7.0), or do you actually have the whole "pH Meter Calibration Kit" with the 3 different liquids or whatever?

I have a pH meter, but never use it. It seems to give me wildly inconsistent readings from the same sample (i.e., I'll test plain tap water and the numbers will vary between 3.5 and 8, or whatever, in seconds).

 

[davidst]

Yeah be careful putting a meter in hot wort, I did that with my first meter and after about 5 batches, I can't get anything close to a consistent reading with it.

 

[dmcman73]

I calibrate my pH meter prior to each use using calibration solution. Not only will it calibrate the meter but it will be a sanity check (a control) that the meter is measuring properly.

 

[Dolomieu]

Do you just calibrate it with distilled water (pH = 7.0), or do you actually have the whole "pH Meter Calibration Kit" with the 3 different liquids or whatever?

I have a pH meter, but never use it. It seems to give me wildly inconsistent readings from the same sample (i.e., I'll test plain tap water and the numbers will vary between 3.5 and 8, or whatever, in seconds).

That sucks, you have my condolences. I don't use one for my brew day but in the lab we most certainly use 4,7, and 10. calibrating with 4 and 10, with a check on the 7. Though the ranges we see are much wider than on brew day. I would imagine a calibration with 4 and 7 would be good for brew day.

I'd look at your manual and see if there are any self-tests protocols or a recommended MV reading for say pH 7 buffer. That's if your meter has a MV. If we saw that occurring in the lab we would replace the probe(if it's an epoxy filled probe) or change out the filling solution and recheck.

If it's a small handheld, I would hazard a guess that those features aren't available to you(Though I could be wrong). To be honest, this is exactly why I don't use a pH meter at home on brew day, though admittedly it is more an excuse than anything. I would only purchase a meter that has a separate probe so that it's health can be checked via MV and can be easily swapped out. The cost of these type of units are just a bit much for my hobby. Though there are pH meters for arduinos and Raspberry Pi's now so maybe i'll just build my own meter some day.

This all said, my original statement holds true. If you can't calibrate it prior to use, just leave it on the shelf. If it's swinging widely check your manual to see if there are any suggested remedies. Maybe even contact the manufacture. You may be able to send it in for service. Usually something is better than nothing, but in this case making adjustments to your mash pH while not having a properly functioning meter will only add to a lack of consistency.

 

[mabrungard]

Be aware that pure water has no ionic content upon which a pH meter needs for proper operation. It is typical for a relatively pure tap water, RO water, or distilled water to display erratic pH readings. Correspondingly, you should never assume that distilled water has a pH of 7.0 since any impurities or contact with the atmosphere will alter its pH.

 

[Dolomieu]

To add to that, RO and Distilled water will have a pH of something closer 6.3-6.5.

Edit: this also should be stated. PH meters, most meters in fact, should not be stored with/in RO or DI water. Most manufacturers will suggest a specified KCl solution for long term storage and pH7 buffer between measurements. Again, read your manual for the specifics of your meter.

 

[kombat]

I broke out my meter again last night just to try it again. I added 20 mL of tap water to the testing cap, as the instructions stated, and turned it on. It read 10.0, then after a few minutes, settled at 9.8. I find it very unlikely that my tap water has a pH of 9.8.

I'm holding out hope that our tap water lacks adequate ions to properly measure its pH. Earlier today, I ordered a pair of bottles of calibration solution (7.0 and 4.0), so when they arrive, I'll check with them and see if my water is just uncooperative for testing, or if my meter is pooched.

 

[Dolomieu]

If this is city tap water, there should be plenty of ions but if you haven't actually used pH buffers to calibrate it, there still is some hope. You can't just buy a meter and run around getting accurate readings. It needs to be properly calibrated before each use. Generally there is also a warm up period, so you may need to leave it on for 15 minutes prior to calibration. If you calibrated to something other than appropriate buffers, it could be a reason you are getting such high pH readings from your tap water. pH that high would be an exceedence of pH criterion most any where I would guess. It's very unlikely that it's above 7.8-8 pH.

Let us know how it goes after you calibrate with pH buffers. Hopefully that will take care of your issues.

 

[chickypad]

I wouldn't assume anything about your tap water if you haven't had it tested. Mine is practically RO water - alkalinity in the 15-20 range and all other ions in single digits based on ward lab report x 3 over the yrs. Per them the pH reading is always over 9. As above, hoping some proper calibration will get your issues fixed.

 

[Dolomieu]

I wouldn't assume anything about your tap water if you haven't had it tested. Mine is practically RO water - alkalinity in the 15-20 range and all other ions in single digits based on ward lab report x 3 over the yrs. Per them the pH reading is always over 9. As above, hoping some proper calibration will get your issues fixed.

You make a great point and I did over look one fact. There are municipal water facilities moving to RO treatment. It's not cheap and causes issues that they have to address in there effluent(brine solution left over from treatment). So my assumption that you would have plenty of ionic constitutes for your meter could be wrong.

 

[ajdelange]

All,
I've been brewing with EZ water calculations for a while, and they have always been spot on as measured with my ph meter. But yesterday, I brewed an all-grain RIS and the mash ph kept reading lower than expected, and a bit inconsistent (calibrated milwaukee ph58 dipped directly into the mash).

A constantly drifting mash pH indicates something is wrong. In such a case the first thing to do is remove the electrode from the sample, rinse it off thoroughly and poke it back into one of the calibrating buffers, preferably 4. If the reading is appreciably different from 4 or if it keeps changing then the electrode is faulty. Many manufacturers publish 'rejuvenation' instructions in their literature which accompanied the meter. These usually involve soaks in acids and/or bases of different strength in order to clean the bulb and junction of fouling deposits. As we work with beer, mash and wort you might want to start with an enzyme based cleaner such as Zymit.

If you can't get the electrode to perform properly in buffers it isn't going to perform elsewhere. It is time to replace it. If it does work in buffers then repeat your mash measurement and it should be good.

So my question is this: since the ph meter measures electrical potential in the solution, would the suspension of the grain in a heavier mash affect the result?

A pH meter measured the redox potential difference between H+ ions in the solution and other ions in the 'leached layer' (the outer layer of glass from which metal ions have been removed) of the glass membrane (bulb) referenced to another electrode which is separated from the sample by a porous plug of some sort. Reference electrolyte must be able to flow from the interior of the reference half cell into the sample. If the junction is plugged somehow this can't happen and readings will be erratic. Similarly, of hydrogen ions can't access the leached layer they can't engage in a redox reaction there and the reading will be erratic. Now the bulb has quite a bit of surface area and a grain or husk particle can't cover it entirely (the way a protein coating can) but a grain or husk particle can block the junction so if you have an erratic reading in mash, check the junction to see if there is something blocking it and wash it away with a squirt from a wash bottle if you find such an obstruction.

There is a fairly complete rundown on the workings of pH electrodes and meters at https://www.homebrewtalk.com/showthread.php?t=302256. That should be enough to clear up most of the misconceptions that one might draw from some of the posts in this thread. I'll hit a few of them in particular in some separate posts.

Thanks.[/QUOTE]

 

[dyqik]

I broke out my meter again last night just to try it again. I added 20 mL of tap water to the testing cap, as the instructions stated, and turned it on. It read 10.0, then after a few minutes, settled at 9.8. I find it very unlikely that my tap water has a pH of 9.8.

I'm holding out hope that our tap water lacks adequate ions to properly measure its pH. Earlier today, I ordered a pair of bottles of calibration solution (7.0 and 4.0), so when they arrive, I'll check with them and see if my water is just uncooperative for testing, or if my meter is pooched.

MRWA water supplying Boston and many surrounding towns is treated to very low ionic content, and the monthly official test data usually reports its pH as 9.8 (Wachusett Metro-Boston). See the last page of last month's report.

From here, the typical pH range for tap water in Ottawa is 8.4 to 8.8. You can check last year's report for your particular system at this page. BTW, this should remove the need for a lab test for the mineral content as well as it looks like the city gives you all the data you should need. The couple of reports I glanced at suggest the water in Ottawa is very low in minerals.

So, no, there's no reason to assume that pH 9.8 is wrong for tap water.

 

[ajdelange]

The ATC correction in most pH meters is only good up to about 110-120 degrees.

ATC 'correction' is not a 'feature' of the modern digital meter; it is an integral part. A modern meter could not function were the ATC equations not built in. As such ATC works from absolute 0 to the temperature of the sun but of course the sensors (RTD and pH electrode) are limited to a finite temperature range. Don't exceed it and try to do everything as close to room temperature as you practically can. This puts you in accordance with convention in the brewing industry and relieves your meter of much potential thermal stress.

 

[ajdelange]

ATC has usefulness in only a minor temperature range, near room temperature.

It is effective at any temperature within the range of what the electrode and RTD can handle.

As the temperature of wort increases, not only does the measurement ability of the probe change (which ATC corrects for)

Ideally, only the slope changes and it does so directly (linearly) with temperature. The equations the meter uses to calibrate itself consider the temperature of the buffers and the sample in computing the slope and offset voltage used to turn a mV reading from the electrode into a sample pH number. The problem arises when the electrodes isoelectric pH is different from the design value of 7. In this case measurements made on a sample at a temperature appreciably different from that of the buffers at calibration may be in error. I say that you are asking ATC to work too hard in those cases but that's just my way of explaining it. In fact, if you know the isoelectric pH you can take measurements at temperatures removed from the calibration buffer temperatures but as explained in several posts here you want to work near room temperature.

So you are kidding yourself in assuming that ATC does any good in the brewery.

Not really. It allows you to calibrate with buffers at 18 and 22° C and to get a good reading at 25 °C. And you can't turn it off anyway.

Cooling your wort to near room temp and allowing the meter's ATC to correct for the minor temperature effects

This is probably to most a very minor point but at the same time a very important one. It isn't correcting anything. It is giving you a pH reading based on a model of the pH electrode response that properly includes the effects of temperature. As noted above, you cannot ask for a raw, uncorrected reading because you cannot turn ATC off. If you want raw data because you intend to interpret it yourself rather than rely on the meter's firmware (this is actually what I do for most work) then record mV and temperature.

 

[ajdelange]

That sucks, you have my condolences. I don't use one for my brew day but in the lab we most certainly use 4,7, and 10. calibrating with 4 and 10, with a check on the 7. Though the ranges we see are much wider than on brew day. I would imagine a calibration with 4 and 7 would be good for brew day.

When working with mash, wort and beer brewers will not encounter pH values higher than 7 and should definitely not calibrate with 4 and 10 buffer checking with 7. But then neither should someone looking at pH in the 7 to 10 range. They should do a three point calibration (4, 7 and 10) developing two pairs of slope and offset cal factors. This insures the best accuracy in both ranges which should be better than the individual tolerances of the buffers by a factor of sqrt*(2) halfway between buffer pairs.

 

[Dolomieu]

When working with mash, wort and beer brewers will not encounter pH values higher than 7 and should definitely not calibrate with 4 and 10 buffer checking with 7. But then neither should someone looking at pH in the 7 to 10 range. They should do a three point calibration (4, 7 and 10) developing two pairs of slope and offset cal factors. This insures the best accuracy in both ranges which should be better than the individual tolerances of the buffers by a factor of sqrt*(2) halfway between buffer pairs.

You are absolutely right and won't fight over this. Not everyone is lucky enough to work with updated or high end enough equipment to do a three point calibrations. I would be surprised if the units most homebrewers are using would do a three point calibration. It also matters what field you are in. My lab is not analytical and our SOP falls inline with our industry and the certificates that apply to it.

 

[beskone]

Things I learned with my PH meter recently (Hana pHep):

Calibrate that sucker before each brew day or you're gonna get wildly inaccurate readings. I use a 4.01 and 7.01 buffer to do a 2 point calibration.

Draw off a sample and let cool to room temp before testing.

Bru'n Waters predicted PH is pretty much dead on when you input your water and additions accurately. (within .01-.02 - within my meters margin of error)

I think the calibration and cooling the wort to test with are the biggest keys. I'm now using the meter just to verify what Bru'n Water tells me. I could see getting away with just using the spreadsheet it's so on the money.

 

[ajdelange]

I would be surprised if the units most homebrewers are using would do a three point calibration.

Brace yourself then. The Hach Pocket Pro+ pH which is quite popular here does 3 point cals (not that brewers need them generally).

 

[Dolomieu]

Brace yourself then. The Hach Pocket Pro+ pH which is quite popular here does 3 point cals (not that brewers need them generally).

If that meter does what you say then I may actually have to pick one up. I don't care for those particular types of meters, just personal preference. I just prefer to be able swap out the probe. Though you supported the statements that I made with: not that brewers need them generally. I was only trying to give some sound, reasonable advice.

 

[ajdelange]

Be aware that pure water has no ionic content upon which a pH meter needs for proper operation. It is typical for a relatively pure tap water, RO water, or distilled water to display erratic pH readings. Correspondingly, you should never assume that distilled water has a pH of 7.0 since any impurities or contact with the atmosphere will alter its pH.

It is true that when the sample has a very high impedance (pure water is at 18 MΩ-cm) noise pickup is more likely and response is slow (you are discharging a capacitor through a large resistance). So what do you do if you need to measure the pH of pure water? Add an ion strength adjuster and calibrate with buffers that have had this ISA added to them. Kits are sold by Hach, Orion... for just this purpose. The ISA is a neutral salt that doesn't shift pH but does increase conductivity.

BUT... you don't need to measure the pH of nearly pure water. It doesn't matter. The reason the pH can go all over the place depending on the CO2 situation is because pure or nearly pure water has no buffering capacity (i.e. no alkalinity other than its own) to speak of. When using RO or DI water in proton deficit/surfeit calculations assume its pH is 7 and its alkalinity is 1000*10^(-pHmash) mEq/L. The error induced by ignoring its actual CO2 content and actual intrinsic pH is nil.

 

[ajdelange]

I broke out my meter again last night just to try it again. I added 20 mL of tap water to the testing cap, as the instructions stated, and turned it on. It read 10.0, then after a few minutes, settled at 9.8. I find it very unlikely that my tap water has a pH of 9.8.

It could. Lots of places, motivated by the Flint stuff-up I suppose, are now sending out water with pH at these levels.

I'm holding out hope that our tap water lacks adequate ions to properly measure its pH.

That's not likely to be the case. For starters if the pH of the water is indeed 10 (let's make the math easier) the OH- ion concentration is 1000 times higher than it is in pure water. Also, the utility had to put something in the water to get the pH to 10 (i.e. they added NaOH or Ca(OH)....) Solutions at pH far from 7 are far from pure. Even RO water with only a few ppm TDS has enough conductivity for a pH measurement but as I indicated in the previous post, you don't really care.

Earlier today, I ordered a pair of bottles of calibration solution (7.0 and 4.0), so when they arrive, I'll check with them and see if my water is just uncooperative for testing, or if my meter is pooched.

There's the ticket.

 

[ajdelange]

If that meter does what you say then I may actually have to pick one up.

I wouldn't get one just because it does three point cal. It is a pretty good meter especially at the price point. There stability check data on it is at https://www.homebrewtalk.com/showthread.php?t=302256.

I don't care for those particular types of meters, just personal preference.

Then you should be aware that you don't dunk the meter in buffer or sample. You pour the buffers and sample into a cup which also serves as a cap.

I just prefer to be able swap out the probe.

The electrode is replaceable but no, you cannot take off the stock electrode and put on, for example, a Na ISE in its place and start taking sodium ion concentration measurements.