The Bar Towel

Hi folks,

With a half wheat / half pils mash, Five Star 5.2 set the mash (using good ol' Toronto tap water) at 5.6 -- rigorously tested with a calibrated probe.

Shortly after the mash started, the pH was 5.68. A few minutes later, 5.9. After the 5.2 was added (per instructions), 5.6. Added some more 5.2 and recirculated the wort, still 5.6.

Now ... 5.6 isn't necessarily a bad pH for mashing, but it is high enough that the finished beer will have more long chain sugars (i.e., sweeter) and fewer short chain sugars (dryer).

The moral of the story, I believe, is that, given Toronto's water chemistry, 5.2 should be called 5.6.

Good info.

I think there's enough calcium carbonate (>100 ppm) in most of Ontario's water to naturally buffer the pH.

I've never played with water chemistry, other than simple dillution with distilled water for some lighter malt grists.

Are you adjusting your PH readings to compensate for temperature?

Also, everything I have read about 5.2 from the experts say that while most 5 Star Products are top notch, 5.2 is junk. I have won a couple tubs of it over the years, and always give it away, so I have no personal experience with it.

markaberrant wrote:Are you adjusting your PH readings to compensate for temperature?

I drained off some wort for each reading and chilled to room temperature (apparently, the temperature of the mash is high enough to shorten the life of a probe). And, because I was anal about it, I kept the probe in the wort for several minutes.

Phosphoric acid, FWIW, is apparently what the pros use to lower pH, but our local suppliers don't stock it.

fishnerd wrote:

markaberrant wrote:Are you adjusting your PH readings to compensate for temperature?

I drained off some wort for each reading and chilled to room temperature (apparently, the temperature of the mash is high enough to shorten the life of a probe). And, because I was anal about it, I kept the probe in the wort for several minutes.

Phosphoric acid, FWIW, is apparently what the pros use to lower pH, but our local suppliers don't stock it.

pH is only weakly affected by temperature. As temperature increases, the extent of dissociation increases (and thus pH decreases). That aside, it would seem that the relevant pH would be the in situ pH of the mash (i.e. the pH of the mash at mashing temperature). So there would be no need to correct for mash pH, so long as you measure the pH at mashing temperature. By cooling to room temperature, you would have driven the acid equilibrium back, and thus increased the pH. Having said that, and depending on the exact composition of your wort, the pH at mashing temperature may have been closer to 5.2 than the 5.6 you measured at room temperature (the extent of the impact of temperature on pH is context dependant, in other words it depends on the exact chemistry of a particular wort). The moral of the story is, 5 Star's pH stabilizer may be a load of BS, but not necessarily a 0.4 pH unit load of BS.

Oh ya, if you use the stuff again, highly recommend you add it to your mash water prior to mash in...you'll achieve a more uniform distribution.

cannondale wrote:pH is only weakly affected by temperature. As temperature increases, the extent of dissociation increases (and thus pH decreases).

I'm pretty sure most PH meters are calibrated for 25C. I'm no expert on all this stuff, check out braukaiser.com and get in touch directly with Kai if you want to get the full scoop.

markaberrant wrote:

cannondale wrote:pH is only weakly affected by temperature. As temperature increases, the extent of dissociation increases (and thus pH decreases).

I'm pretty sure most PH meters are calibrated for 25C. I'm no expert on all this stuff, check out braukaiser.com and get in touch directly with Kai if you want to get the full scoop.

Ahh, didn't realize your were talking about temperature correction for the probe itself, as opposed to the mash temperature. That's a completely seperate phenomenon. I was spoiled with auto-correcting pH meters for too long, and hence have taken that for granted for years.

So in summary, mash pH should be measured at mashing temperature (although the affect of temperature is minimal). Then, if you don't have an auto-correcting pH meter, you have to do a temperature correction for your measured pH.

cannondale wrote:So in summary, mash pH should be measured at mashing temperature (although the affect of temperature is minimal). Then, if you don't have an auto-correcting pH meter, you have to do a temperature correction for your measured pH.

Except ...

Many brewing sources assume that the optimal 5.2ish pH is with room temperature wort because of how temperature and pH mingle about.

I poked around earlier today -- pretty much no one gets Five Star's product to hold a mash at 5.2. The chemistry behind the product is flawed.

FWIW, I normally do add salts and the like before the grains, but I was trying to nail down some problems with recent fermentations and wanted a LOT of data points about what was going on in the mash. No more of this 2 tbsps of magic powder per 5 gallons of finished beer BS.

Edit: 2 tbsps, or whatever the package says.

fishnerd wrote:

cannondale wrote:So in summary, mash pH should be measured at mashing temperature (although the affect of temperature is minimal). Then, if you don't have an auto-correcting pH meter, you have to do a temperature correction for your measured pH.

Except ...

Many brewing sources assume that the optimal 5.2ish pH is with room temperature wort because of how temperature and pH mingle about.

I poked around earlier today -- pretty much no one gets Five Star's product to hold a mash at 5.2. The chemistry behind the product is flawed.

FWIW, I normally do add salts and the like before the grains, but I was trying to nail down some problems with recent fermentations and wanted a LOT of data points about what was going on in the mash. No more of this 2 tbsps of magic powder per 5 gallons of finished beer BS.

Edit: 2 tbsps, or whatever the package says.

In Brewing Science and Practice Briggs states that the pH of a cooled wort sample at room temperatures compared to the pH of the same wort at saccharification rest temperatures is 0.35 higher [Briggs, 2004]. That explains some of the differences of mash pH reported in the (home brewing) literature. He reports that the pH optimum for most fermentable worts is between 5.1 and 5.3 when measured at mash temperatures (65C/149F) and 5.4 - 5.7 at room temperature (25C/77F).


Sounds like that 5 Star product may be doing a great job for you after all..

cannondale wrote: Sounds like that 5 Star product may be doing a great job for you after all..

I doubt it. I also let the probe sit in the wort as it was chilling. The pH drift going from 65 down to 22 / 23 wasn't particularly pronounced, certainly less than .3.

Any chance you'd be willing to use 5.2?

fishnerd wrote:Any chance you'd be willing to use 5.2?

I have and I would.

Interesting that the pro's use phosphoric acid (food grade phosphoric acid is very easy to come by, check online) to adjust pH. Where the 5 Star 5.2 stabilizer is meant to control the pH (it's a buffer), phosphoric acid is not a buffer, and would have to be continually added to adjust the pH to the desired level. That would be difficult to do without 'real time' pH readings. If you ever end up trying the phosphoric acid, be sure to let us know how it worked out and how you used it.