Pre-testing portion of mash for pH

I'm looking for some suggestions for the best way to do a test mash with a small portion of the grain bill to determine pH. I see where some people use nested containers on the stove like a metal pan in a larger pot of warm/hot water. I am assuming:

Scale down grain bill to about a pound of the base malt and reduce everything from there including water and water additions from Bru'n Waters' recommendations. Heat the treated mash water in one pan to strike, add grain, and set this pan in 2nd pan with warm/hot water to maintain mash temp. Take pH readings every 10 minutes to see where the pH finally levels out (probably around 30 - 45 mins ,assuming a 60 min mash). Make acid/base adjustments as necessary to reach target pH, I guess scaling down from what it would take to vary pH by .1 in Bru'N Waters' recommendations for the full sized batch. I would add about 1/2 of that, stir well, wait a couple of minutes and test again, then add the rest, if necessary. Have I got this right?

I read that some folks only make adjustments if pH is outside the 5.2 - 5.6 range. Thoughts here?

From here do I just scale up the additions I made to get to desired pH to full batch, sticking with the original Bru'N Water batch treatments changing only the adjustment additions? Or do I do something to change my Bru'N Water inputs?

BTW, I have a Milwaukee 102 and would calibrate it before starting.

Why not just adjust the PH in the first 5 minutes of pouring in your strike water with lactic acid? I just take a shot glass sample from the mash after I dough in and get that sample down to 77 degrees by putting the shot glass in a bowl full of ice and stirring with my thermometer. Takes about a minute to get it from 155 degrees to 77. I test the PH and then adjust from there with lactic acid. I aim for a 5.3-5.4 to start but it is fine to be 5.2-5.6.

Because mash pH doesn't start to approach its equilibrium until 20 - 30 minutes in after which it is generally too late. pH measured in the first 5 minutes can be way high or way low relative to its final value in the first 5 minutes.

OP's inclination towards a test mash is good sense. Use a pound or half a pound of grain in an appropriate amount of water at the desired strike temperature. Hold at this temp for about 20 minutes if you can (beaker, metal if you have one, in a water bath is great but not strictly necessary). Be sure the grist portion is well mixed. This can be tricky but if your grain bill is 3% sauermalz and your mash sample isn't you won't get the right pH.

"Mash" for 20 minutes, mix well, withdraw a sample of the liquid, cool to room temp and measure pH. If you are off note that the buffering of mash is, for purposes of computing a correction, about -40 mEq/kg•pH and that lactic acid is about 12.8 N to mash pH. From this you can calculate the amount of extra acid needed scaled up for the whole mash pH_error*kg_malt*40/12.8 mL.

When I adjust within the first 5 minutes, like many do, I don't think this is a practice that is erroneous. I measure my sparge PH and its in range (5.2-5.4) from the adjustment at dough in, and then measure my kettle PH before boiling and it is still in range (5.2-5.4). Both the of the PH measurements post dough in are way past the 20-30 minute equilibrium you talk of. I think developing a mini mash to predict your PH could be effective, but I also think that it is extra work for no reason. In both practices, you will most likely make the same exact beer.

Come to think of it, I have rarely even had to make adjustments after doughing in. I put the estimated amount of lactic acid that Beersmith tells me to put in based upon the grains and the water profile in the strike water before I pour it in my mash tun. This method usually gets me in range withour further adjusting.

A skilled brewer shouldn't need to do a test mash. He should know from his previous experience with the materials he uses about where the mash pH should fall. Venturing into terra incognita might be an exception to this.

New guys don't have any experience. They must rely on a calculator, recipe advice or a test mash. As the test mash is obviously the most reliable of the three I advocate that for such brewers.

I do test mashes when I do a totally new recipe, but tend to rely on notes the second, third, tenth, etc time I make a recipe.


When I DO use a test mash, I bring my little scale and a Solo cup into the LHBS and measure out 10% of each ingredient. 8 lbs of 2-row for the main mash, 363 g for the test mash. .5 lb of c-40 for the main, 22.5 g for the test.

That's probably more trouble than most people take but it's certainly the best way to make sure that the test mash matches the main.

ajdelange said:

[...]If you are off note that the buffering of mash is, for purposes of computing a correction, about -40 mEq/kg•pH and that lactic acid is about 12.8 N to mash pH. From this you can calculate the amount of extra acid needed scaled up for the whole mash pH_error*kg_malt*40/12.8 mL.

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Thanks for that. I'd thus be inclined to change my current test mash strategy and not attempt any mash pH adjustment - just the "salt" additions - then see where the result falls and use the math above for production.

Reasonable? Or is there a pitfall which I'm missing?

Cheers!

New guys don't have any experience. They must rely on a calculator, recipe advice or a test mash. As the test mash is obviously the most reliable of the three I advocate that for such brewers.

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I'm the OP. While I've been brewing for a long time, I'm a new guy to testing and adjusting pH to my brewing. AJ, I've read your sticky on pH Meter Calibration and Use. That's been very helpful in setting up brew day testing procedures. A great article. I use Bru'n Water.

I have 2 brews so far and have been "well off" between estimated pH and measured pH on both brew days. I calibrate the meter each brew day morning. The first difference I chalked up to getting familiar with using the new meter (Milwaukee 102). Before the 2nd brew I spent time using the meter and I ran a calibration check as recommended in 11b of AJ's sticky. The 2nd brew (a robust porter) was off by .3 (Bru'n Water 5.5 and measured 5.2, stabalized about 20 mins in).

At this point it was suggested that I do a test mash, which led me to this post. I am not a Chemist, but I understand that the estimated pH in Bru'n Water is calculated from the lovibond values of the grist bill. I don't have enough experience yet as some of the other posters have, but .3 difference seems pretty large.

FYI, I have a 3 keggle, single tier, 2 pump system so I can circulate my mash. I have been pulling my test samples from the top in a pyrex container and filtering into a small glass after recirculating and stirring. My water has been tested by Ward labs.

"Mash" for 20 minutes, mix well, withdraw a sample of the liquid, cool to room temp and measure pH. If you are off note that the buffering of mash is, for purposes of computing a correction, about -40 mEq/kg•pH and that lactic acid is about 12.8 N to mash pH. From this you can calculate the amount of extra acid needed scaled up for the whole mash pH_error*kg_malt*40/12.8 mL.

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Not being a chemist, could you tell me how to translate this into quantities please?

dmcmillen said:

The 2nd brew (a robust porter) was off by .3 (Bru'n Water 5.5 and measured 5.2, stabalized about 20 mins in).

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Interesting. What version of Bru'n Water were you using? The acidity assumed for roast grains was too low in the older versions and was increased in the most recent versions. Your result in that robust porter isn't entirely surprising if you used an older version.

Pretesting a small portion of a mash should be a more accurate way to assess and adjust mash pH. But that is a big PITA in my opinion. The good thing about the models used in some mashing chemistry calculators is that they are close enough to truth. However, asking any model to accurately predict pH to less than about a tenth of a unit, is unreasonable.

I recently laughed at one person's contention that their model predicted pH accurately to a hundreth. It turns out that it doesn't...they precalibrate each grain addition's pH response in order to get that accuracy. Again, this seems to be like a lot of work. But if you feel that getting pH to within a hundreth is important, then this is what you'll have to do. The variation in malt acidity is inherent in those products and add to that, the potential for water supplies to vary, and it's not reasonable for any model to predict that closely.

While a good commercial brewer should be measuring and adjusting their processes and additions to reduce the variation in their successive batches, many homebrewers don't rebrew the same batch time after time. The opportunity to know and refine processes and additions is limited for us. That's why having a tool that gets your result into an acceptable range with the first batch is important. We may not be brewing that beer with those identical ingredients and water for months or years...if ever. It's unreasonable for most of us to assume that we will have the luxury of prior experience to guide our mashing chemistry adjustments.

dmcmillen said:

I have 2 brews so far and have been "well off" between estimated pH and measured pH on both brew days. I calibrate the meter each brew day morning. The first difference I chalked up to getting familiar with using the new meter (Milwaukee 102). Before the 2nd brew I spent time using the meter and I ran a calibration check as recommended in 11b of AJ's sticky. The 2nd brew (a robust porter) was off by .3 (Bru'n Water 5.5 and measured 5.2, stabalized about 20 mins in).

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You will note that as you take more and more pH measurements they tend to make more sense even though you are not consciously doing anything differently from the first measurements you made. A pH meter is an instrument. You don't pick up a violin for the first time and crank out the Bach Partitas. Same here (broadly).

dmcmillen said:

At this point it was suggested that I do a test mash, which led me to this post. I am not a Chemist, but I understand that the estimated pH in Bru'n Water is calculated from the lovibond values of the grist bill. I don't have enough experience yet as some of the other posters have, but .3 difference seems pretty large.

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It is and while the models in Brun water are quite capable of 0.3 error when you see an error of that magnitude you should suspect that it may be 'headset' error rather than a problem with the program. That error could be in data entry or in pH measurement or both.

dmcmillen said:

Not being a chemist, could you tell me how to translate this into quantities please?

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OK. Let's say you have a mash containing 10 kg of grain and have mashed 0.5 kg of the grist with the appropriate amount of water and find the pH to be 0.3 units too high (low). Given the buffering of mash is about 40 mEq/kg•pH you conclude that you need 10*.3*40 = 120 mEq of acid (base). Given that the acidity of 88% lactic acid is 12.8 mEq/mL you conclude, in the too high case, that you should add 120/12.8 = 9.3 mL lactic acid. In the too low case you would turn to sodium bicarbonate which, with its equivalent (molecular) weight of 84 mmol/gram, implies that you need 120/84 = 1.42 gram of that.

Since you are not certain about the 40 mEq/kg•pH buffering of the mash you would measure out say 3/4 of the amount of acid or base as required and add that to the main mash. Or, if you have the patience, do another test mash with those amounts, scaled by 20 for an 0.5 kg mash and see where you fall.

Martin, I used 1.16 for that brew. I have downloaded 1.18 and will use that in the future.

AJ, thanks for the primer. Will take a bit of practice/study to get good with the math.

dmcmillen said:

Martin, I used 1.16 for that brew. I have downloaded 1.18 and will use that in the future.

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You can revisit the pH prediction using the newer version and you are likely to see that the prediction is much closer to the measured value. Don't worry, its still beer.

ajdelange said:

If you are off note that the buffering of mash is, for purposes of computing a correction, about -40 mEq/kg•pH and that lactic acid is about 12.8 N to mash pH. From this you can calculate the amount of extra acid needed scaled up for the whole mash pH_error*kg_malt*40/12.8 mL.

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Trying to ensure I understand the math portion of what Bru'n Water is doing so I have a better grasp of the calculation and think I understand this. Wanted to send back what I see and get feedback to ensure I am not missing something.

I have attached my water report, grain bill, what it looks like with no water adjustment and then the water adjustment one.

Using the calculation above I see that I am .7 off my desired PH of 5.3. And my grain bill includes 9.5lbs of grain which is ~ 4.3kg. So .7*4.3*40/12.8 = 9.4ml of lactic acid to correct this.

Bru'n Water says 10.8ml will get my mash to 5.35 which I think is within reason for a calculator.

My questions about this are as follows...

1) Are my calculations correct?

2) Does the amount of water being used play a part in the numbers being off? To me it seems to be an acceptable amount off but I have not adjusted my water before. I have it set up to do no sparge with 8.33 gallons of water to 9.5lbs of grain so a really thin mash.

3) I am using the information off the grain I will be using for the grain bill when it comes to the levi bond information. Is there a better way to calculate that then using the information off the bag?

4) Does the test mash have to be at the same water to grist ratio?

5) Can I use a mix of lactic acid and phosphoric to keep the amounts down needed to treat the water or does mixing them have unintended consequences?

I know this is a advanced forum and some of the questions might be based on my lack of knowledge of water adjustment. Hopefully I can use this to catch up and at least get a rudimentary understanding of what I am doing instead of just tossing in stuff.

Thanks,
Jeff

JDL said:

Using the calculation above I see that I am .7 off my desired PH of 5.3. And my grain bill includes 9.5lbs of grain which is ~ 4.3kg. So .7*4.3*40/12.8 = 9.4ml of lactic acid to correct this.

My questions about this are as follows...

1) Are my calculations correct?

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If the actual buffering of the mash, including the water, is 40 mEq/kg of grain then yes. But of course it isn't. That's an approximated number based on the average of several malts I have measured and does not include the buffering of the water. Is the spreadsheets's number better? If it more accurately determines the buffering of the mash and uses a proper calculation method then yes. Otherwise, no.

JDL said:

2) Does the amount of water being used play a part in the numbers being off? To me it seems to be an acceptable amount off but I have not adjusted my water before. I have it set up to do no sparge with 8.33 gallons of water to 9.5lbs of grain so a really thin mash.

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If the water has appreciable alkalinity, then yes. If you are using RO then no.

JDL said:

3) I am using the information off the grain I will be using for the grain bill when it comes to the levi bond information. Is there a better way to calculate that then using the information off the bag?

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The best way is to measure the buffering of the malt as the Lovibond rating is a poor proxy for it. But this is a tiresome process and is essentially making a test mash for each grain and combining the result. It is easier to do a test mash for the actual grist you are going to mash.

JDL said:

4) Does the test mash have to be at the same water to grist ratio?

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Yes. It should, except for scale, be identical to the actual mash to the fullest extent possible.

JDL said:

5) Can I use a mix of lactic acid and phosphoric to keep the amounts down needed to treat the water or does mixing them have unintended consequences?

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Yes. Can't think of unintended consequences.

Thanks for the quick response.

Between you and martin I think the key you have said time and time again rings true, using the information as a starting point and then through experience with each recipe you dial it in, just trying to get that starting point to not be dump worthy beer.

Definitely going to test mash the first few recipes/styles I do though to help.

Thanks,
Jeff

That is significant alkalinity in that tap water, so the dose of lactic is not a surprise. It's getting near the threshold where most tasters can detect it. If you like the taste of lactic acid, you may find that the proposed lactate level is desirable. I do like it. If you don't relish the lactate flavor, then using a portion of phosphoric acid or diluting the water with RO is recommended.

Don't forget to treat the sparging water since that will drive the kettle wort pH up and the resulting beer pH is likely to be higher also. It won't be as crisp as that style should be.