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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > pH and Lactic Acid Calc Confusion
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Old 06-19-2011, 09:05 PM   #1
redwood
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Default pH and Lactic Acid Calc Confusion

Hello all!

Alright, we just had our summer wit go into the fridge, and pulled a sample...and there's something off about it. We figured it's time to address water quality, as we haven't been looking at pH at all. After much reading and note taking, I have this example set up, but it seems to be excessively high. Can anyone point me in the right direction?


Latic acid at 88% in solution drops pH by .1 at .09036g of lactic acid/lb of grain.

Water pH is 7.0, we want pH of 5.6, so a drop in pH of 1.4 is needed.

.09036g/.1pH drop = Xg/1.4 pH drop needed

x=1.31g needed for every lb of grain to get it to drop to 5.6.

There are 1214mg/mL in lactic acid. This is equal to 1.214g/mL, or in 1mL/1.214g.

If we intend on 5 lbs of grain, then 5 x 1.31g x 1mL/1.214mL=5.39mL needed to add.


That seems like quite a bit when most people I saw were adding only 1-3mL. Anyone have any input?

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Old 06-20-2011, 03:11 AM   #2
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That rule of thumb regarding pH drop per percentage of acid malt is not accurate. The alkalinity of the water has a huge impact on pH change and any attempt to place a rule of thumb on it is folly. It cannot be done.

You need to use an acidification calculator to figure out how much of an acid your water needs. Unfortunately, that sort of calculator needs information on the water alkalinity. Information on the water pH is helpful, but is far less important than the alkalinity. Bru'n Water has an acidification calculator included in the many tools it contains.

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Old 06-20-2011, 04:18 AM   #3
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Quote:
Originally Posted by mabrungard View Post
That rule of thumb regarding pH drop per percentage of acid malt is not accurate. The alkalinity of the water has a huge impact on pH change and any attempt to place a rule of thumb on it is folly. It cannot be done.

You need to use an acidification calculator to figure out how much of an acid your water needs. Unfortunately, that sort of calculator needs information on the water alkalinity. Information on the water pH is helpful, but is far less important than the alkalinity. Bru'n Water has an acidification calculator included in the many tools it contains.
Wow, thanks! If one sparges until preboil volume is reached, or until 1.010 SG, how do you figure out how determine acid addition if you don't know exactly how much sparge water you're going to use? Just have 5 gallons ready of sparge and add acid to match that as calculated?
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Old 06-20-2011, 02:32 PM   #4
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Brewing programs like Beersmith and ProMash have nice calculators for the volume of sparging water needed. Take that sparging volume and treat that entire volume with acid as needed to reduce the alkalinity to an acceptable level. That typically implies a water pH between 5.5 and 6.0.

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