Ph rise after mash in

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silobran

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Hi,
First of all i have calibrated my ph meter every time before use, second i lowered ph of strike water with lactic acid from 7.8 to 6.5 which resulted in mash ph 5.9. Next time i added a bit more acid, ph was 5.8. I kept adding more acid till i reached 5.3 which was good enough for me. Next brew i added same amount of acid to strike water. After mashing in(after 30min) i measured mash ph and it was 5.3. i saved a sample of acidified strike water which had ph of 4.2. Thought i made a mistake, so i measured again next time brewed and ph result were the same.

Is this normal? As far as i understand mash ph the grain should lower ph not raise it.
 
Mash (and most organic systems) have a ton of buffers that absorb or give off H+ around one particular pH or another. Determining equilibrium is actually an entire semester of "analitical chemistry" in college!

While strike water of 4.2 seems a little low, that it rose with addition of grain is not surprising.

(edit: and if strike pH that low works, then roll with it. I actually don't measure strike pH, so I may just be clueless. Do you measure pH 15m into mash? That's generally considered best practice 'round these parts.)
 
This is going to depend on your grain. The only types of grain that I know lower PH are acidalated specialty grain and you don't need a whole lot.

In any calculator I have ever used to calculate PH, grains always bring the PH to a higher number. In this way if you ever end up adding too much acid you can account by adding extra grain.
 
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fwiw, blackened grains will definitely lower mash pH and can be problematic. It's why it is often recommended to hold them back for most of the mash duration and add them at the end. This is possible because there's literally nothing that's going to be "converted" in grains that are chocolate to black in color (~250-600 SRM)...

Cheers!
 
Mash (and most organic systems) have a ton of buffers that absorb or give off H+ around one particular pH or another. Determining equilibrium is actually an entire semester of "analitical chemistry" in college!

While strike water of 4.2 seems a little low, that it rose with addition of grain is not surprising.

(edit: and if strike pH that low works, then roll with it. I actually don't measure strike pH, so I may just be clueless. Do you measure pH 15m into mash? That's generally considered best practice 'round these parts.)
Exactly! The grain and its dissolving constituents produce a strong buffer system. The rise in wort pH is typical in pale grists since the acidity of the strike liquor has to be somewhat high to overcome that buffering and keep the mash pH somewhat low. This phenomena can be reversed if the acidity of the GRIST is high (aka: dark grist) and the strike liquor alkalinity has to be high to help avoid the wort pH from dropping too low.

With regard to the pH of strike water, it's not a good measure for assessing if the water is right for your mash. If you start with a very low alkalinity water source such as distilled or RO water, a small acid addition can easily drop the water's pH to under 4. If you're brewing a pale beer, the pH of the strike liquor can easily be under 4. The mash buffering will eventually bring the overall wort pH up as the starches, sugars, proteins, and other matter dissolve from the grain into the wort.

Wort pH DOES change during the course of a mash and it takes around 30 to 45 minutes for it to reach its equilibrium. You can't take a dough in wort pH reading and assume its where it'll end up. Even a 15 minute pH reading is relatively inaccurate and you can't even assume that the final pH will be higher or lower than its early reading due to the grain acidity issue mentioned above (pale vs dark).

The bottom line is that employing a water chemistry calculation based on the source water chemistry and overall grist composition is more likely to be accurate in the end, than using a treated source water pH reading.
 
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