[JT]

Would love to know why this never seems to be even relatively close for me... switched from lactic acid adj to acid malt, only got worse!
RO water.  Total adj in 9.5 gallons (mash and sparge) is 2 grams gypsum, 2 grams calcium chloride, 1.9 grams Epsom salt. 

[RPIScotty]

How accurate are your volume inputs?

[JT]

Calibrated scales for weighing salts, grains.  Sight glass on kettles for water, which I've verified for accuracy. 

[mabrungard]

That is quite a difference. If you have any of those base malts left, you should perform a distilled water assessment on both. The water to grist ratio needs to be within the range of normal mashes. I suggest something close to 3 ml of distilled water for every gram of malt. Size that sample to provide enough wort to enable a pH measurement. The DI wort pH should be around 5.7 to 5.8 for those very pale base malts. I'm betting that their pH won't be in that range.

I've heard that Weyermann had a mistake at their facility and some very acidic malts were shipped as base malt.

[JT]

I think I need to do two tests.  One with distilled water, one with my RO water.  Something has to be driving this pH down, my guess is on either the malt or the water, and I'm leaning toward the water since this has been an ongoing issue for me among different malsters. 

[mabrungard]

RO water does not typically result in a lower than predicted mash pH. However, if the RO water has a high concentration of dissolved CO2, it can be more acidic than expected. Gases will permeate through RO membranes at a high rate and if the feed water has high CO2, it will exhibit in the RO water.

[JT]

RO water does not typically result in a lower than predicted mash pH. However, if the RO water has a high concentration of dissolved CO2, it can be more acidic than expected. Gases will permeate through RO membranes at a high rate and if the feed water has high CO2, it will exhibit in the RO water.

Is there an easy test for this?  I'd measure the pH, but I don't know how reliable that would be considering it's RO...

[pfabsits]

It is always possible that the pH meter is off. A pH reading of 5.49 is not that much different from 5.05. It is easy to get this kind of discrepancy from a variety of factors including:

Age of the pH buffers - the calibration is only as good as the buffer. If the buffer is off then the pH reading will be off. For people that use a pH meter on an infrequent basis (1X/month) then I would recommend buying the buffers in sachets/packets. Each packet when opened is fresh.

Proper hydration of the electrode - Before using the probe it is important that it is hydrated. As long as the probe was stored in a storage solution then the hydration layer will be present. If the probe dried out then it is important to soak in buffer or storage solution for 2-3 hours to re-hydrate the glass and junction.

Age of the electrode - pH electrodes do not last forever or at least maintain an acceptable offset and slope. This is one of the most critical parts for an accurate pH measurement.  An offset (pH 7) potetnail should be between +/- 30 mV and the slope (difference from pH 7 to 4) potential should be greater than 160 mV (90%) slope.  If a pH electrode is not within these specs then it is completely possible to be a 0.5 pH units off. With a tester it is difficult to determine offset and slope. If the the Milwaukee tester has a default cal then it might be possible to calculate from the pH readings in buffers after performing a default calibration. Otherwise it would be recommended to replace the pH probe on a yearly basis. It would be safe to assume that the probe will always be within the specs stated unless the meter is being abused (used at temps >70-80 ^oC, allowing to dry out).

The probe should be cleaned periodically with cleaning solution. If the offset is known then it would be easy to know when to clean. Typically wen the value drifts outside the +/- 30 mV range it is due to a coating on the electrode. Another indicator of a probe that needs to be cleaned is when the readings are very erratic and taking a very long time to stabilize. At that point the probe should be cleaned.

If you have a new meter that has been properly hydrated and the calibration buffers are fresh then the reading displayed is probably within 0.05 - 0.1 pH.

As far as using RO water versus DI water, there really should not be a difference. This assuming that the RO membrane is not shot and is able to do its job. A basic TDS meter can be used to check. It would be expected to see a reading between 10-20 ppm (20-40 uS/cm). Both RO and DI will have relatively low ion content. Both will have low alkalinity/acidity.  In fact, high purity water is so sensitive that technically it is to be pH 7 but carbon dioxide in the air will form carbonic acid and lower the pH. It is difficult to measure pH of high purity water since there are no ions present to complete the electrical circuit but the pH will decrease and become more acidic as it is exposed to air. The acidity level  is still very low so anything (acid/base) added to the water will change the pH. For example a drop of vinegar will cause a relatively large decrease in pH since the water has no buffering capacity.






 

[JT]

It is always possible that the pH meter is off. A pH reading of 5.49 is not that much different from 5.05. It is easy to get this kind of discrepancy from a variety of factors including:

Age of the pH buffers - the calibration is only as good as the buffer. If the buffer is off then the pH reading will be off. For people that use a pH meter on an infrequent basis (1X/month) then I would recommend buying the buffers in sachets/packets. Each packet when opened is fresh.

Proper hydration of the electrode - Before using the probe it is important that it is hydrated. As long as the probe was stored in a storage solution then the hydration layer will be present. If the probe dried out then it is important to soak in buffer or storage solution for 2-3 hours to re-hydrate the glass and junction.

Age of the electrode - pH electrodes do not last forever or at least maintain an acceptable offset and slope. This is one of the most critical parts for an accurate pH measurement.  An offset (pH 7) potetnail should be between +/- 30 mV and the slope (difference from pH 7 to 4) potential should be greater than 160 mV (90%) slope.  If a pH electrode is not within these specs then it is completely possible to be a 0.5 pH units off. With a tester it is difficult to determine offset and slope. If the the Milwaukee tester has a default cal then it might be possible to calculate from the pH readings in buffers after performing a default calibration. Otherwise it would be recommended to replace the pH probe on a yearly basis. It would be safe to assume that the probe will always be within the specs stated unless the meter is being abused (used at temps >70-80 ^oC, allowing to dry out).

The probe should be cleaned periodically with cleaning solution. If the offset is known then it would be easy to know when to clean. Typically wen the value drifts outside the +/- 30 mV range it is due to a coating on the electrode. Another indicator of a probe that needs to be cleaned is when the readings are very erratic and taking a very long time to stabilize. At that point the probe should be cleaned.

If you have a new meter that has been properly hydrated and the calibration buffers are fresh then the reading displayed is probably within 0.05 - 0.1 pH.

As far as using RO water versus DI water, there really should not be a difference. This assuming that the RO membrane is not shot and is able to do its job. A basic TDS meter can be used to check. It would be expected to see a reading between 10-20 ppm (20-40 uS/cm). Both RO and DI will have relatively low ion content. Both will have low alkalinity/acidity.  In fact, high purity water is so sensitive that technically it is to be pH 7 but carbon dioxide in the air will form carbonic acid and lower the pH. It is difficult to measure pH of high purity water since there are no ions present to complete the electrical circuit but the pH will decrease and become more acidic as it is exposed to air. The acidity level  is still very low so anything (acid/base) added to the water will change the pH. For example a drop of vinegar will cause a relatively large decrease in pH since the water has no buffering capacity.

Calibration solutions are individual packets.  Meter is calibrated prior to use.  It has an auto-off feature, so I re-calibrate it each time it shuts off.  I am curious as whether this is necessary, but haven't found any info on it. 

Meter is always stored in storage solution in the cap and is soaked in cleaning solution after each use.  Electrode is fairly new (within the last 12 months).  Temp range of tested wort is always between 65 and 75° F. 

Every time I've tested my RO with TDS meter it's been under 20.  The dispensers are regularly serviced.  I've not tested the pH of it for the same reasons you stated, but I still plan on doing a side by side RO & distilled pH test with a mini mash of the same grain. 

The other wild card I suppose would be the salts themselves?  Maybe there's an acidic element or contamination to my gypsum or calcium chloride causing a greater pH drop than the software is accounting for?  Any way to test these?

[HoosierBrew]

I still plan on doing a side by side RO & distilled pH test with a mini mash of the same grain. 

I'm curious to see how the readings come out.

[brewinhard]

I've heard that Weyermann had a mistake at their facility and some very acidic malts were shipped as base malt.

I still wouldn't be surprised if this was your issue.  I think Wort-hog also had some issues when using some Avanguard malts too.. IIRC>

[pfabsits]

You do not need to re-calibrate each time the meter turns off. Calibration compensates for any changes to the pH electrode. Unfortunately, changes do occur. pH calibration should be performed before use. So if you use once a day/week or month then the meter should be calibrated. If in a production environment were the meter is used throughout the day then it should be calibrated once per shift. 

Calcium chloride should have no impact on pH unless contaminates are present. There is a method to measure water less than 100 uS/cm.Basically high purity KCl is added to the sample to increase EC so that the pH can be read. High purity KCl will not affect the pH of the solution. I would think the same for CaCl2

On the other hand the gypsum might lower pH since it is composed of sulfate. If sulfate is converted to sulfuric acid then the pH will go down. I am not a chemist so the information would have to be confirmed as to whether sulfate in water can be converted to sulfuric acid.

What might be a good experiment to try is to make two solutions, one with calcium chloride and the other with the gypsum. Measure the pH of each solution then add a drop of vinegar to each. If the pH decreases then the water has no to little buffering capacity (low alkalinity) and the effect on pH is somewhat negligible. If the pH stays the same then the water is buffered against acid. A base, like ammonia, can be used to check the acidity. Not to know the exact acidity but whether the solution has enough to buffer against any chemicals/substances that would change the pH.

It is important to note that pH is not the same as acidity and alkalinity.  The pH is the hydrogen ion activity while acidity and alkalinity is the buffering capacity or resistance to change of a solutions' pH when adding a chemical to it. For example regular orange juice and low acid orange juice will both have a pH of 3.9 to 4.0. The citric acid in orange juice is what determines the pH. They differ in the concentration of citric acid in which the low acid has a lower concentration than regular orange juice. The low acid orange juice will take less base to reach a pH 8.2 endpoint than regular orange juice. 

Not sure if this info helps. It might be as simple as it was stated that eh malt could be in question. Contacting the company with the lot number should be able to help determine if there was a production issue.

[JT]

Good to know on the calibration piece.  That was annoying and a little time consuming. 
I'm really surprised the major breweries haven't demanded some sort of acidity number to be attached with each lot.  As in x weight of this grain mixed with y amount of distilled water should equal a pH of ... I guess the burden must be on the brewery to test but you'd think that info would be useful to the brewery ahead of time, given they all use different water sources and could then plan to adjust water according.

[hopfenundmalz]

I've heard that Weyermann had a mistake at their facility and some very acidic malts were shipped as base malt.

I still wouldn't be surprised if this was your issue.  I think Wort-hog also had some issues when using some Avanguard malts too.. IIRC>

Best had problems with Pils malt being contaminated with acidualted malt. Weyermann also?