Strange pH readings in mash

[spook100]

I did a brew yesterday and saw some really strange things happening with my mash pH that I'm hoping someone can explain.

I prepared a batch of brewing water and treated it with phosphoric acid to bring the pH down to 5.6. I then mashed in with around half of it and a grain bill that was 100% maris otter. On taking a pH reading about 15 minutes into the mash the pH had gone *up* to 5.8. I though I had cocked up my water treatment so went back and tested the rest of the water that was to used for the sparge and it was still at pH 5.6. I then tested the pH meter in buffer solution and it was reading accurately. Went back to the mash water (about 45 minutes in) and it was still reading around 5.8.

Any ideas what may have caused this?

[Dave S]

I did a brew yesterday and saw some really strange things happening with my mash pH that I'm hoping someone can explain.

I prepared a batch of brewing water and treated it with phosphoric acid to bring the pH down to 5.6. I then mashed in with around half of it and a grain bill that was 100% maris otter. On taking a pH reading about 15 minutes into the mash the pH had gone *up* to 5.8. I though I had cocked up my water treatment so went back and tested the rest of the water that was to used for the sparge and it was still at pH 5.6. I then tested the pH meter in buffer solution and it was reading accurately. Went back to the mash water (about 45 minutes in) and it was still reading around 5.8.

Any ideas what may have caused this?

The pH of the water is not particularly relevant. It is the pH of the Mash from the reactions of the grist with the water that matters. What was the alkalinity and Calcium levels of your water before mixing in with the grist?

[spook100]

The pH of the water is not particularly relevant.

Agreed. I didn't think it was possible for the pH to go up after mashing though - I thought it would either stay the same or drop.

Calcium is around 50ppm.
Alkalinity 102ppm of CaCO3.
Residual alkalinity 65ppm CaCO3

[Eric]

Yes, pH is not quite the ideal measure for brewing water. That said, it's the way it is done in the US and they seem to make it work except it's not easy to follow and requires quite sophisticated software to do what otherwise would be relatively simple.

Further to this, after comparing pH of natural waters with their alkalinity, a pH of 5.6 should result in a level of alkalinity close to what is required for pale mashes, although not precisely so and is what you are finding. If your water was to have more calcium the mash pH would be lower, maybe less than the pH of the mash water.

If you could take some pure water it would have a pH, in theory, of 7.0 and if you mashed that with pale malt you would find mash pH to be about 5.9 or 6. If you then added a small amount of acid to that same pure water, with it's very little buffering power the resultant pH would fall significantly, let us say to pH 5.0. If you then mashed with that in the same way as with the untreated water you would find the mash pH much as the first.

[simple one]

I did a brew yesterday and saw some really strange things happening with my mash pH that I'm hoping someone can explain.

I prepared a batch of brewing water and treated it with phosphoric acid to bring the pH down to 5.6. I then mashed in with around half of it and a grain bill that was 100% maris otter. On taking a pH reading about 15 minutes into the mash the pH had gone *up* to 5.8. I though I had cocked up my water treatment so went back and tested the rest of the water that was to used for the sparge and it was still at pH 5.6. I then tested the pH meter in buffer solution and it was reading accurately. Went back to the mash water (about 45 minutes in) and it was still reading around 5.8.

Any ideas what may have caused this?

This has happened often with me, to the point I wait with pH meter and acid ready for the 10 min point.

I find pH if not taken seriously leads to hazes. Don't care about eff, just add more malt.

[Eric]

I wait with pH meter and acid ready for the 10 min point.

I find pH if not taken seriously leads to hazes. Don't care about eff, just add more malt.

Adding acid 10 minutes into the mash is a bit like fitting a condom prior to conception but post ejaculation. The avoidable can still happen.

Yes, haze is one of many problems caused when mash pH is outside the acceptable range.

Efficiency will suffer only marginally due to an unacceptable mash pH.

[Robwalkeragain]

I assume you're reading at 20c with a calibrated reliable thermometer...

[spook100]

I assume you're reading at 20c with a calibrated reliable thermometer...

The meter was calibrated the night before and when I tested in a buffer solution after the problem arose it was still reading accurately. I did let the wort cool before testing but not all the way to 20C because the meter is supposed to have automatic temperature correction. Maybe the ATC isn't as good as advertised.

[Aleman]

ATC is not supposed to compensate for extremes. If you calibrate at 20C then I wouldn't rely on ATC to give a decent reading beyond 25C

[simple one]

With reference to the condom simile.

Are we saying all damage is done in the first ten minutes with an incorrect pH. Focusing mainly on tannin extraction and precipitating proteins?

Can it not be regained?

[Eric]

With reference to the condom simile.

Are we saying all damage is done in the first ten minutes with an incorrect pH. Focusing mainly on tannin extraction and precipitating proteins?

Can it not be regained?

It's difficult to imagine any lipids or tannins released during a period of excess pH would return to their original condition when a more normal pH is achieved. The object of adding acid is to reduce or eliminate alkalinity in the brewing liquor while adding it directly to the mash will result in acid making contact and reacting with all ingredients. Protein mostly precipitates in the kettle.

The influence of acid added to water can be determined while when added to a mash one might only guess.

[Robwalkeragain]

I assume you're reading at 20c with a calibrated reliable thermometer...

The meter was calibrated the night before and when I tested in a buffer solution after the problem arose it was still reading accurately. I did let the wort cool before testing but not all the way to 20C because the meter is supposed to have automatic temperature correction. Maybe the ATC isn't as good as advertised.

It's a possibility, purely by chance I read about ATC the other day and the difference between hot wort at 65c and 20-25c pH is about 0.3. so what was your wort in kettle pH?

[spook100]

It's a possibility, purely by chance I read about ATC the other day and the difference between hot wort at 65c and 20-25c pH is about 0.3. so what was your wort in kettle pH?

The wort in the kettle was around 65c. However, I removed some of the wort and set it aside to cool a bit before taking the reading. I would guess it was around 40C when I took the reading.

[simple one]

The mash will naturally gravitate to a pH dependant on its variety of malts.

This also takes in to account mash thickness, available calcuim and original alkalinity.

Great information on it http://braukaiser.com/wiki/index.php/Be ... nd_mash_pH

From what i have read, it is not abnormal for a pale malt only recipe to rise up in pH, especially if you are looking to hit 5.2.

[simple one]

Hence often on a lot of brewing software, an all pale recipe will need to be of a negative alkalinity to drop the pH low enough to compensate for a rise in pH.