Sudden problems predicting mash pH

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Eric
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Re: Sudden problems predicting mash pH

Post by Eric » Sat Jan 05, 2019 2:58 pm

chrisr wrote:
Sat Jan 05, 2019 12:18 pm
I've ordered a Salifert alkalinity kit.

Eric, What does a TDS meter do for me, brewing-wise. I've just read up what it meaures, but how does that relate to brewing? (There's always something new to learn about brewing, isn't there?)

Do you mean take the sample later on in the mash? At what time? I know there are a lot of reactions under way in the first stages of the mash, and the pH will change. I thought 10 mins would see it settled.These 'problem' brews have been a different recipe every time; stouts to pale ales.

I mash around 2.5-3.0 l/kg.

I'm not trying to hit a precise pH, and I don't obsess about that, I just want it to fall into the optimum range, reliably.
What a TDS Meter will do for you is difficult to guess, but for water supplies that vary as much as mine can and does, it is a godsend. A quick dip of the meter into a water sample with both at room temperature gives an instantaneous reading of total dissolved solids in mg/L assuming the dissolved solid is sodium chloride. Now while this reading will not be accurate for those minerals in drinking water, it increases as the mineral content does and vice versa. This enables swift determination of the mineral levels every brew day and decide the action necessary to correct alkalinity. After treatmentalkalinity is measured using a Salifert kit and any necessary final adjustment is then made. In this way I know with decent accuracy the mineral content of the liquor used in every brew.

10 minutes might be sufficient to obtain a good enough reading for your purposes, mine are taken later when they should be more consistent. However, I fly sparge intent to obtain near maximum extraction when it is essential to avoid pH rising above 5.7 or extract unwanteds and later readings help achieving that objective.

Stouts and pales have vastly different pH if mashed with similar liquors, but I'll assume you make provision for this. One observation is from what I have read, dark malts and roasted adjuncts used in North America appear to be far less kilned than those in common use in UK which would mean any fixed calculation embeded in software would be prone to giving spurious predictions.
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Re: Sudden problems predicting mash pH

Post by PeeBee » Sat Jan 05, 2019 3:25 pm

mabrungard wrote:
Sat Jan 05, 2019 3:57 am
Have you changed your mashing thickness? If you've moved to a thinner mash, that does affect mashing pH and I can report that current versions of Bru'n Water do not predict pH very well when the mash thickness is thinner than about 4 liter/kg. There is testing and recalibration currently being conducted to improve the program's prediction capability in thin mashes. Mashing in the 2 to 4 l/kg range should be fairly accurate.
As someone else suffering from recent failures of the calclators to predict pH (my issue being the opposite to Chris's in that I'm getting lower pH, not higher): Is there anything else in mooorland water that can sway the pH predictions apart from the usual salts?

Bru'n Water also predicted my mash pH very well before 2018. And I'm always well within the optimum mash thickness range.

My issue pre-dates the drought experienced by the UK last Summer. Playing with the dissolved salts doesn't seem to replicate (simulate) such low pH in Bru'n Water; mineral acid additions do though!

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Re: Sudden problems predicting mash pH

Post by chrisr » Sat Jan 05, 2019 3:41 pm

TBH, I'm not getting this TDS thing. It's used it as a quick check just to test if the water composition has changed since last brew day? And all it is measuring is the total mineral content of the water? That would seem, to me, to be more a useful thing to do in a hard water area.

Anyone any advice on the best time to take the mash sample?

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Re: Sudden problems predicting mash pH

Post by Aleman » Sun Jan 06, 2019 1:21 pm

10 to 15 minutes into the mash! ... TBH as long as you are consistent when you take it, then it shouldn't matter too much, as long as you quote the time when you have taken the sample because the pH will vary depending on time ;)

The salifert kit is actually quite accurate even in water with little in it, like we have here in Lancashire most of the time! I've actually compared it against a sample sent to Neil (wallybrew), titrated against analytical grade HCl using a biurette and triple calibrated pH Meter, using the methyl orange test ... another titration, and phenolpthlein a third titration. all the results agreed within expected limits so I'm confident that the Salifert kit is more than adequate ... especially if you use the more 'accurate' method taking a 4ml sample.

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Re: Sudden problems predicting mash pH

Post by mabrungard » Tue Jan 08, 2019 4:55 am

Mash pH increases throughout the mashing duration. Through a large number of mashing trials and a review of my previous brewing results, I now know that pH increases by about 0.2 and 0.4 units in the period between the 15 minute and 45 minute pH measurements. Therefore, don't rely on the 15 minute reading as your standard. Expect that the 15 minute measurement will be low and continue to monitor pH and you'll see that it will rise during the mash.

By the way, the pH deviation is larger when you brew with thin mashes. Thicker mashes have somewhat more stable pH response during the mashing period.
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Re: Sudden problems predicting mash pH

Post by Aleman » Tue Jan 08, 2019 8:59 am

What Martin is saying is correct, which means that when you report the pH, or attempt to predict it you must specify the time into the mash that the reading was/should be taken ... Otherwise no one else will know if your, or their, result is meaningful or an anomaly.

This was drummed into me during my degree courses. ... Standardise the method !!! Standardise the method !!! Otherwise your results are meaningless!!!

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Re: Sudden problems predicting mash pH

Post by chrisr » Tue Jan 08, 2019 6:52 pm

So what does they actually mean when I read (for example): "In particular we want to keep the measured pH of our mash in the 5.2-5.5 range with a preference towards the lower end (5.2)."? What 'measured pH' are they referring to? You are saying the time the measurement is taken will influence the result, so what is the measurement time that could be taken to provide 'the measured pH'?

Martin says the pH could change by up to 0.4 between 15 and 45 minutes into the mash so whichever way it's planned, worst case, it's possible the mash is in the 'optimum' range at one measurement time, and out of it at the other?

So how is it possible to stay within what's generally regarded as 'optimum' for the whole (or even most of) the mash? Is it possible?

Or looking at it another way, it would be possible to take a sample at a time that ensured the mash (appeared) to be in the optimum pH range, even though for the majority of the mash period, it wasn't.

I'm not meaning I want to predict and get an exact mash pH, but I do want the mash to fall into the range consided optimum.

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Re: Sudden problems predicting mash pH

Post by Aleman » Tue Jan 08, 2019 9:32 pm

Thats why I like authors who asay stuff like a sample of the mash taken after 10-15 minutes should be between pH 5.2 and 5.7 ... No Bullshit, and using a series of test mashes and water treatments you can determine what treatments do that for grist you've chosen.

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Re: Sudden problems predicting mash pH

Post by chrisr » Sat Jan 12, 2019 5:44 pm

Well, the Salifert test (at double precision) gave the same result for alkaninity I was already working with: 12 mg/L CaCO3.

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Re: Sudden problems predicting mash pH

Post by PeeBee » Sat Jan 12, 2019 7:24 pm

chrisr wrote:
Sat Jan 12, 2019 5:44 pm
Well, the Salifert test (at double precision) gave the same result for alkaninity I was already working with: 12 mg/L CaCO3.
But that's good! If you were doubting one report, It's not so easy to doubt two agreeing reports.


I actually got a reasonable mash pH today, 5.5. But that was a mash of only 5Kg grain (1Kg oat husks) for a 20L batch, and mashing in the full brew length of water so it might not be representative. No barley, but that's clutching at straws (but not barley straw) thinking that would make a difference.
Aleman wrote:
Tue Jan 08, 2019 8:59 am
What Martin is saying is correct, ...
What??? When I saw this thread with you and Eric in it, and then Martin ambles along I thought it was time to climb into the bomb shelter :wall . But you are agreeing with him :shock: ?

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Re: Sudden problems predicting mash pH

Post by chrisr » Sat Jan 12, 2019 8:16 pm

I'm brewing tomorrow, an APA, so no dark malts. Used Bru'n Water to setup the water, double-checked it. We'll see what happens...

I'll sample more than one time, this time.

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Re: Sudden problems predicting mash pH

Post by Aleman » Sun Jan 13, 2019 12:38 pm

PeeBee wrote:
Sat Jan 12, 2019 7:24 pm
Aleman wrote:
Tue Jan 08, 2019 8:59 am
What Martin is saying is correct, ...
What??? When I saw this thread with you and Eric in it, and then Martin ambles along I thought it was time to climb into the bomb shelter :wall . But you are agreeing with him :shock: ?
No Martin is completely correct the pH does change in the mash with time ... the issue I have is at what point in the mash is the correct time to take the mash PH. If we all take it at the time it's 'correct. (*), whatever that time is, then we are all in agreement, and can pat ourselves on the back as to being excellent brewers. In reality though, unless you have very expensive properly calibrated industrial probes and are continuously measuring pH then you are never going to know what the pH is. ... The best we can do is to use a 'standard' method and time to take the sample. Now the vast majority of brewing books I have quote "A sample of the mash, taken between 10 to 15 minutes into the mash, should have a pH in the range 5.2 to 5.7. That's good enough for me, and most of my mashes are on the money, those that are not are those where I am following a traditional process ... Like triple decoction ... where you actually wait for the mash to be a particular value after doughing in, before you start the process.

In an ideal world we would all quote the time, and temperature of the sample as well as the actual pH recorded ... Don't get started on the should the pH be taken at room temperature or mash temp, and then do you adjust it back to the other temperature and quote it!!


(*) That is the pH Value is what we expect, or some software predicts as correct ;)

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Re: Sudden problems predicting mash pH

Post by chrisr » Sun Jan 13, 2019 12:50 pm

Today's brew: all pale malts, so no complications. Brun Water predicted pH5.36. pH measured at room temperature, at both 10 and 15 mins was 5.59. Meter recalibrated before measurements and checked again afterwards. At the end of the mash (75mins), pH5.51.

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Re: Sudden problems predicting mash pH

Post by guypettigrew » Sun Jan 13, 2019 1:34 pm

Seems OK, within normal range (according to Aleman). Although odd how it decreased. Thought pH usually increased during the mash.

Were you happy with it?

Guy

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Re: Sudden problems predicting mash pH

Post by Aleman » Mon Jan 14, 2019 9:09 am

It's in the acceptable range, at the beginning and end, why worry??

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