The more I think about the 0 effective alkalinity method of pH control the more I like it to the point where I'd like to propose the following description of it as a Sticky.
When adding acid to a mash to adjust its pH to a desired value, pHz, the amount of acid added is the sum of the acid additions required to do the following:
The amount of acid required for Item 3) for each malt is easily calculated from the malt's DI mash pH, pHz and some malt buffering parameters which must have been measured or estimated using the method outlined at http://wetnewf.org/pdfs/Brewing_articles/MBAA_FREDERIC.pptx or a similar method.
In the usual approach to the problem the brewer obtains a water report from a laboratory and punches the results into a calculator or spreadsheet. He then puts data about the malts he intends to use into the same spreadsheet which calculates the sum of the 3 acid components and reports them to the user. The problems with this approach are four:
There is, of course, a catch and that arises in the situation where the 0 alkalinity calculation demands a negative acid (base) input because of acidic grains. Here you will have to think a bit and do some calculations so some readers may wish, in this case, to revert to the usual method when it arises. What follows is for the rest.
When you acidify your water to pHz you are measuring its alkalinity to pHz, not the standard value required by the published procedures for alkalinity measurement, but it is with pHz that we are concerned. Once the water is at pHz its alkalinity to mash pH is 0.
At this point I think an example will be beneficial. For the example I am going to use metric for volumes and mEq for alkalinity and proton measurement because that makes things so much simpler as you will see if you try to convert everything to other units.
Lets say your target pH is 5.4 and you treat 40 L of water with 7.0 mL of 88% lactic acid to reach this pH. The following table gives the strength (Normality = mEq/mL) of 88% lactic acid at various pH values
pH N
4.5 9.59
5.2 11.26
5.3 11.36
5.4 11.45
5.5 11.51
8.0 11.77
At pHz=5.4 88% lactic acid is 11.45N and in using 7 mL of it you added 7*11.45 = 80.15 mEq of protons to your 40 L of water for 80.15/40 = 2 mEq/L Note that I have included the normality at pH 4.5 which is the ISO standard pH for alkalinity determination. Had you continued adding acid to that pH you would have used 9.418 mL equating to 90.31 mEq/40L or 2.26 mEq/L. That's 112.0 ppm as CaCO3 (multiply mEq/L by 50) which is the ISO alkalinity. Note, of course, that you needen't use lactic acid for this nor do you need to use the whole volume of water you intend to treat. You could very well have used 100 mL of the water with 0.1N acid sold for alkalinity determination Just be sure to get the alkalinity at pHz (and at 5.4 if you like). But as you will need at least some of the treated water you might just as well get your alkalinity measurement from the larger volume. The important thing is that you know your alkalinity to pHz: 2.0 mEq/L.
Having determined your water's alkalinity to pHz is 2.0 mEq/L you can then have your calculator tell you how much acid to add for your grain choices. If it tells you to add a base such as bicarbonate then you have the situation we are talking about and you must figure out how much proton absorbing capacity it wants you to add. To do this zero out any acid or base additions you have made and incrementally add sodium bicarbonate until the program predicts mash pH of pHz. Most of the calculators are not sophisticated enough to realize that the strength of sodium bicarbonate as a base depends on pH any more than they are aware that the strength of lactic acid does (the pH 8 entry in the lactic acid table above is what your spreadsheet will assume the strength of lactic acid to be). Therefore, take the sodium bicarbonate recommendation and divide it by the molecular weight of sodium bicarbonate, 84 mg/mmol, and assume that the program wants that many mEq protons to be absorbed. For example, if the program requires 3.5 grams (3500 mg) of sodium bicarbonate to reach pH 5.4 then assume it wants 3500/84 = 41.7 mEq proton absorbing power in the mash water. Suppose you plan to mash with 12 L of water. Clearly your treated water with proton absorbing power at pHz of 0 won't do so you simply take 12 L more of your untreated tap water which has 2 mEq/L*12L = 24 mEq proton absorbing capacity and add (41.7 - 24)*84 = 1486.8 mg sodium bicarbonate to it. The other 40 L you prepared has 0 alkalinity WRT mash pH and is thus suitable sparge, makeup or dilution water.
Finally we consider the case where the program wants less alkalinity than found in 12 L of your tap water (24 mEq) say 10 mEq. In this case just measure out the amount of tap water necessary to give those 10 mEq (10/2 = 5L) and add enough (7 L) of the treated water (of 0 alkalinity) to make up to the mash water volume of 12 L.
When adding acid to a mash to adjust its pH to a desired value, pHz, the amount of acid added is the sum of the acid additions required to do the following:
- Change the distribution of the water's H+ and (OH)- ions to that dictated by pHz.
- Change the distribution of H2CO3, HCO3- and CO3-- to that dictated by pHz.
- Change the distribution of malt acid system ions to that dictated by pHz.
The amount of acid required for Item 3) for each malt is easily calculated from the malt's DI mash pH, pHz and some malt buffering parameters which must have been measured or estimated using the method outlined at http://wetnewf.org/pdfs/Brewing_articles/MBAA_FREDERIC.pptx or a similar method.
In the usual approach to the problem the brewer obtains a water report from a laboratory and punches the results into a calculator or spreadsheet. He then puts data about the malts he intends to use into the same spreadsheet which calculates the sum of the 3 acid components and reports them to the user. The problems with this approach are four:
- The water report's parameters will be in error due to imperfect measurement technique (these errors are usually fairly small)
- What comes out of the tap on brew day may be substantially different from what came out on the day the tested sample was drawn due to source variations.
- The calculator/spreadsheet's model of the carbonic system may be naive (usually causes small error)
- As actual malt measurements are few and doing them oneself requires a substantial investment in time and equipment the malt models available to most brewers are not very accurate.
There is, of course, a catch and that arises in the situation where the 0 alkalinity calculation demands a negative acid (base) input because of acidic grains. Here you will have to think a bit and do some calculations so some readers may wish, in this case, to revert to the usual method when it arises. What follows is for the rest.
When you acidify your water to pHz you are measuring its alkalinity to pHz, not the standard value required by the published procedures for alkalinity measurement, but it is with pHz that we are concerned. Once the water is at pHz its alkalinity to mash pH is 0.
At this point I think an example will be beneficial. For the example I am going to use metric for volumes and mEq for alkalinity and proton measurement because that makes things so much simpler as you will see if you try to convert everything to other units.
Lets say your target pH is 5.4 and you treat 40 L of water with 7.0 mL of 88% lactic acid to reach this pH. The following table gives the strength (Normality = mEq/mL) of 88% lactic acid at various pH values
pH N
4.5 9.59
5.2 11.26
5.3 11.36
5.4 11.45
5.5 11.51
8.0 11.77
At pHz=5.4 88% lactic acid is 11.45N and in using 7 mL of it you added 7*11.45 = 80.15 mEq of protons to your 40 L of water for 80.15/40 = 2 mEq/L Note that I have included the normality at pH 4.5 which is the ISO standard pH for alkalinity determination. Had you continued adding acid to that pH you would have used 9.418 mL equating to 90.31 mEq/40L or 2.26 mEq/L. That's 112.0 ppm as CaCO3 (multiply mEq/L by 50) which is the ISO alkalinity. Note, of course, that you needen't use lactic acid for this nor do you need to use the whole volume of water you intend to treat. You could very well have used 100 mL of the water with 0.1N acid sold for alkalinity determination Just be sure to get the alkalinity at pHz (and at 5.4 if you like). But as you will need at least some of the treated water you might just as well get your alkalinity measurement from the larger volume. The important thing is that you know your alkalinity to pHz: 2.0 mEq/L.
Having determined your water's alkalinity to pHz is 2.0 mEq/L you can then have your calculator tell you how much acid to add for your grain choices. If it tells you to add a base such as bicarbonate then you have the situation we are talking about and you must figure out how much proton absorbing capacity it wants you to add. To do this zero out any acid or base additions you have made and incrementally add sodium bicarbonate until the program predicts mash pH of pHz. Most of the calculators are not sophisticated enough to realize that the strength of sodium bicarbonate as a base depends on pH any more than they are aware that the strength of lactic acid does (the pH 8 entry in the lactic acid table above is what your spreadsheet will assume the strength of lactic acid to be). Therefore, take the sodium bicarbonate recommendation and divide it by the molecular weight of sodium bicarbonate, 84 mg/mmol, and assume that the program wants that many mEq protons to be absorbed. For example, if the program requires 3.5 grams (3500 mg) of sodium bicarbonate to reach pH 5.4 then assume it wants 3500/84 = 41.7 mEq proton absorbing power in the mash water. Suppose you plan to mash with 12 L of water. Clearly your treated water with proton absorbing power at pHz of 0 won't do so you simply take 12 L more of your untreated tap water which has 2 mEq/L*12L = 24 mEq proton absorbing capacity and add (41.7 - 24)*84 = 1486.8 mg sodium bicarbonate to it. The other 40 L you prepared has 0 alkalinity WRT mash pH and is thus suitable sparge, makeup or dilution water.
Finally we consider the case where the program wants less alkalinity than found in 12 L of your tap water (24 mEq) say 10 mEq. In this case just measure out the amount of tap water necessary to give those 10 mEq (10/2 = 5L) and add enough (7 L) of the treated water (of 0 alkalinity) to make up to the mash water volume of 12 L.
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