LaMotte Water Kit Reliability

[reuliss]

Folks:

I just purchased the LaMotte water kit (the one that includes the ph meter). I wanted to share the water profile I recorded using this kit, along with some ph results from a subsequent brew session. I was little surprised by ph results in real world, so I'm wondering if water kit is reliable, or if the results actually make sense given my test results. Anyway, here goes:

After the test, I got the following water profile:

Cal: 0 (kit only shows results if 50 ppm interverals)
Mg: 12
Na: 33
Chl: 50
SO4: 0 (same as Cal; only shows 50 ppm intervals)
Alkalinity as CaCO3 : 50
PH. 7.1

I use the advanced water calculator on brewers friend. I target mash ph of 5.4 and aim to adjust sparge water ph to 5.4 as well (I use to have a nasty astringency issue--it disappeared once I started adjusting ph of sparge water). The following additions are water brewers friend told me would get mash and sparge ph of 5.4:

Mash: 17 lbs grain, color 5.9, and 8 gal of sparge wate: Add 5 g gypsum and 5 g cal. chl, and 1 ml of lactic acide. I did not get 5.4 with this. Instead I got 5.7. Test 10 minutes later showed 5.75.

Sparge: to 3.5 gal, I added 1 ml of lactic. This brought my sparge water all the way down to 4.7! I had to add tap water back in to bring ph up to targeted 5.4.

So, is the issue my test results from the LaMotte kit, is it brewers friend, or is it my ph meter?

A little more on the ph meter. Up until this last batch, I used colorphast strips. And, in fact, I still used them to compare to what the meter from the LaMotte kit was returning (I did calibrate meter, BTW). Colorphast strips, true to reputation, returned results nearly .5 lower than the meter included with LaMotte kit.

For whatever it's worth, here is my water profile according to my local water report:

Ca: 36
Mg: 9
Na: 20
Chl: 41
SO4: 37
Alkalinity (as CaCO3): 80

Finally, I'll say that, at least according to the colorphast strips, I was coming under on my ph using the water report numbers as well. I never did a brew with a ph meter using the water report figures.

So, anyone have any sense of what I should be addressing first in order to get more predictable results?



Thanks in advance!

 

[ajdelange]

There are lots of possible explanations for what you have observed. The most telling observation is that water pH dropped to 4.7 when you added 1 mL (presumably 88%) lactic acid to 3.5 gal. This says that the alkalinity of the water is 40 which is comfortingly close to the 50 you measured with the LaMotte kit and disconcertingly half what your water supplier told you it should be. As you have two pieces of evidence (acid addition and kit measurement) that the alkalinity is actually around 50 you might do well to assume that number for the time being. A supply's actual alkalinity can vary quite widely from season season.

Using that number with some malt calculations reveals that indeed you could expect a mash pH as high as 5.8 if all the grain were, say Munton's Maris Otter or as low as 5.65 were it all Crisp Maris Otter or something in between were it some other base malt or lower if some higher kilned malts were used as well. The expected pH depends a lot on the pH of the base malt clearly and on the acidities of any other malts used, the amounts of acid added etc. Note that as 88% lactic acid is about 12 N the 1 mL you used provides about 12 mEq of acid (to pH 5.65) whereas 6 gallons of water at alkalinity 50 would require 19 mEq of acid to reach pH 5.65 with Crisp Maris Otter requiring another 13.5 (and Munton's another 70).

It would be well to subject the pH meter to the calibration and stability checks described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/. If it passes those then there is nothing inconsistent with the numbers you observed. Obviously the Brewer's Friend calculation is a bit out of whack so as it is usually pretty good you are not telling it the same things I think you are telling me. I don't really know how much of what malt you used with how much water for example. I've just made some assumptions.

 

[reuliss]

There are lots of possible explanations for what you have observed. The most telling observation is that water pH dropped to 4.7 when you added 1 mL (presumably 88%) lactic acid to 3.5 gal. This says that the alkalinity of the water is 40 which is comfortingly close to the 50 you measured with the LaMotte kit and disconcertingly half what your water supplier told you it should be. As you have two pieces of evidence (acid addition and kit measurement) that the alkalinity is actually around 50 you might do well to assume that number for the time being. A supply's actual alkalinity can vary quite widely from season season.

Using that number with some malt calculations reveals that indeed you could expect a mash pH as high as 5.8 if all the grain were, say Munton's Maris Otter or as low as 5.65 were it all Crisp Maris Otter or something in between were it some other base malt or lower if some higher kilned malts were used as well. The expected pH depends a lot on the pH of the base malt clearly and on the acidities of any other malts used, the amounts of acid added etc. Note that as 88% lactic acid is about 12 N the 1 mL you used provides about 12 mEq of acid (to pH 5.65) whereas 6 gallons of water at alkalinity 50 would require 19 mEq of acid to reach pH 5.65 with Crisp Maris Otter requiring another 13.5 (and Munton's another 70).

It would be well to subject the pH meter to the calibration and stability checks described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/. If it passes those then there is nothing inconsistent with the numbers you observed. Obviously the Brewer's Friend calculation is a bit out of whack so as it is usually pretty good you are not telling it the same things I think you are telling me. I don't really know how much of what malt you used with how much water for example. I've just made some assumptions.

Aj, thank you so much for your response! I admit that you lost me a bit in the second paragraph, but to the extent it's useful, I used 15 lbs Briess 2 row, 1 lb munich 10L, 1 lbs carapils, and .5 lb crystal 40L. 8 gals in mash. 3.5 gal sparge.

What most confuses me most is why I my actual ph was high in the mash but low in the sparge. Is there a rational explanation for that?

 

[reuliss]

There are lots of possible explanations for what you have observed. The most telling observation is that water pH dropped to 4.7 when you added 1 mL (presumably 88%) lactic acid to 3.5 gal. This says that the alkalinity of the water is 40 which is comfortingly close to the 50 you measured with the LaMotte kit and disconcertingly half what your water supplier told you it should be. As you have two pieces of evidence (acid addition and kit measurement) that the alkalinity is actually around 50 you might do well to assume that number for the time being. A supply's actual alkalinity can vary quite widely from season season.

Using that number with some malt calculations reveals that indeed you could expect a mash pH as high as 5.8 if all the grain were, say Munton's Maris Otter or as low as 5.65 were it all Crisp Maris Otter or something in between were it some other base malt or lower if some higher kilned malts were used as well. The expected pH depends a lot on the pH of the base malt clearly and on the acidities of any other malts used, the amounts of acid added etc. Note that as 88% lactic acid is about 12 N the 1 mL you used provides about 12 mEq of acid (to pH 5.65) whereas 6 gallons of water at alkalinity 50 would require 19 mEq of acid to reach pH 5.65 with Crisp Maris Otter requiring another 13.5 (and Munton's another 70).

It would be well to subject the pH meter to the calibration and stability checks described at https://www.homebrewtalk.com/f128/ph-meter-calibration-302256/. If it passes those then there is nothing inconsistent with the numbers you observed. Obviously the Brewer's Friend calculation is a bit out of whack so as it is usually pretty good you are not telling it the same things I think you are telling me. I don't really know how much of what malt you used with how much water for example. I've just made some assumptions.

Aj, thank you so much for your response! I admit that you lost me a bit in the second paragraph, but to the extent it's useful, I used 15 lbs Briess 2 row, 1 lb munich 10L, 1 lbs carapils, and .5 lb crystal 40L. 8 gals in mash. 3.5 gal sparge.

What most confuses me most is why I my actual ph was high in the mash but low in the sparge. Is there a rational explanation for that?

 

[ajdelange]

What most confuses me most is why I my actual ph was high in the mash but low in the sparge. Is there a rational explanation for that?

Yes. The pH depends on the balance of acids and bases in the mash or in the water. For a particular pH each mash component: water and each malt has a proton deficit (the quantity of protons required to establish the component at the particular pH) or surfeit (negative deficit - the quantity of protons the component will yield up if its pH is increased to the particular pH). The same is true for the sparge water you treat though in the sparge water the only components are the bicarbonate ion and the acid you add. The pH of either mash or water is that particular pH which causes the sum of the proton surfeits to be equal to the sum of the proton deficits.

If you tell a calculator that your water has an alkalinity of 80 when its alkalinity is actually only 50 then the calculator will estimate a pH higher than the actual pH for a given acid addition because the proton deficit for a given level of alkalinity is less the higher the pH. Conversely, if you tell a calculator that you are using malts with proton deficits smaller than the malts' actual proton deficits the calculator will calculate a pH lower than actual.

We strongly suspect that your water's alkalinity is closer to 50 than 80 because your Lamotte kit gave you that answer and the pH shift you saw when you acidified the sparge water is consistent with an alkalinity of 40. If you told the calculator the water's alkalinity is 80 it would either predict a higher pH than what you saw or, for an entered pH, tell you more acid is required than is needed.

...to the extent it's useful, I used 15 lbs Briess 2 row, 1 lb munich 10L, 1 lbs carapils, and .5 lb crystal 40L. 8 gals in mash. 3.5 gal sparge.

With respect to the malts: no calculator can know the particulars (proton surfeits or deficits) of any particular malts you are using but can only guess as to what they might be based on similar malts the program's creator has measured or some correlation with color. Neither is particularly accurate and so mash pH prediction programs can't be expected to give very accurate results. As an example of this I indicated in the previous post that the choice of Maris Otter from two maltsters could result in a pH prediction difference of 0.15 pH. As I don't have any data on any of the malts you used I could only guess as to which of the base malts I do have data on most closely approximates Briess 2 row. Same for the other malts. The answer I would come up with probably wouldn't be any better than what you came up with using the calculator you used.

As you have a pH meter the best thing to do is to make a small (1 pound grist) test mash and measure its pH. You can use a spreasheet or calculator to help you see how much of a shift in pH that eliminating the water's alkalinity might have or what the relative effect of using a darker crystal malt might be to give you sime guidance on how to vary the fomulation in order to hit a different pH but you shouldn't rely on the calculator/spreadsheet to give you an accurate absolute value.

 

[reuliss]

Thank you, aj.