Taking pH of Mash with meter

[bobbytuck]

I know there are many, many posts atout this -- but I'm still confused about what I'm looking for when folks talk about "mash pH".

I found this in my notes (copied from another forum -- not mine -- but I don't have a link):

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Measuring pH at mash temperature (lets say 65°C)

Target: 5.2-5.4 Acceptable +/- 0.1

Measuring pH at room temperature (lets say 21°C)

Target: 5.4 - 5.6 Acceptable +/- 0.1

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Is this an adequate summary of the potential points for taking a pH reading?

I also understand that room temp readings are the norm and that taking tghe temp at mash pH even with an ATC pH meter is simply not good for the meter itself. So room temperature is the goal.

Now, in general, when people talk about a mash with pH of 5.2 -- are they talking about 5.2 @ mash temp? I assume -- but I'm not clear -- at least not totally. (This would mean an acceptable room temperature pH of 5.4-5.5 or so).

I know, too, that EZ Water makes its best-guess of pH with the disclaimer that the estimate is at room temp.

Given all this, how does take the actual measurement? I assume I can remove a portion of the mash, let it cool (perhaps set it in a bowl of ice to cool quickly) and then wait until it's in the 68F range.

But I should make reading off this cooled sample, correct? And then if my additions and dilutions are correct, this *room temperature* sample should be in the 5.4 to 5.6 range (not, I presume, in the 5.2 range at room temp -- which would indicate a pretty acidic mash.)

Is this reasoning reasonable?

 

[ajdelange]

You've pretty much got it. But don't worry if you aren't within a ±0.1 pH range. You have a fair amount of latitude so 5.2 at room temp isn't cause to dump the batch by any means. Let's say that 5.3 - 5.5 may be desirable but 5.2 - 5.6 is OK.

 

[SpanishCastleAle]

Given all this, how does take the actual measurement? I assume I can remove a portion of the mash, let it cool (perhaps set it in a bowl of ice to cool quickly) and then wait until it's in the 68F range.

I use a 1/4 cup stainless steel measuring cup. I just stick it in the freezer and set a timer for 4-5 minutes. As long as it's between ~60*-75* F I call it good and don't sweat getting any more accurate than that.

I also make sure the probe is well rinsed with DI/RO water right before I measure. I don't want any residual buffer from the calibration solutions or the storage solution to affect the readings.

 

[bobbytuck]

How long does the mash have to be at the optimum pH?

I usually mash for 90 mins -- but I'm assuming I want to make all these adjustments and measurements as soon as possible?

 

[lamarguy]

I usually mash for 90 mins -- but I'm assuming I want to make all these adjustments and measurements as soon as possible?

Correct, as soon as you mash-in.

FWIW, once you measure a few mashes and adjust your process, you'll find your need to take later measurements is all but gone.

 

[MNDan]

I don't think mash pH should ever be specified without the corresponding temp measured, but no one ever seems to remember what a difference it makes.

My first attempts at water adjustment this year resulted in a mash pH of 5.2@70F and it turned out fine. 5.4-5.6@70F is what I shoot for, though, and from what I've read is the most desirable.

 

[bobbytuck]

So, I brewed a porter today. Recipe:

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Grain bill:

8.5# pale malt
01# Crystal 120
00.5# Chocolate

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To the mash, I added:
1g gypsum
1g cacl2
1ml lactic acid

SRM: 23
OG: 1.059

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Calibrated my new pH meter with 4.01 and 7.01 a few hours before I started brewing.

My pH readings were as follows:
Mash pH: 5.58 @ 70f
pre-boil (after fly sparge): 5.61 @ 70F
Post-boil: 5.35 @ 70F

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Are those pH readings in line for a porter? They seem high -- at least higher than I expected via the EZ water spreadsheet (around mash pH of 5.3 is what I was expecting).

Are they in line for a porter? Or should I look to adding a bit more acid next time?

 

[ajdelange]

The spreadsheets seem to underestimate pH pretty consistently for dark beers so the fact that the spreadsheet and meter disagree by 0.28 is not surprising (to me anyway). OTOH 5.58 is not an unreasonable value. Beer should be fine. Next time you might want to add a bit more acid. As you are using liquid you could do it on the fly i.e. add a couple tenths of a mL, wait, check, add another couple tenths etc until you get to 5.4 or so. What's the alkalinity of the untreated water?

 

[bobbytuck]

Untreated alkalinity is 107.

 

[ajdelange]

Roger that. If your water comes in at pH 7 and if you treat 5 gallons it would take about 3 mL of 88% lactic acid to get the pH of the water alone to 5.4. If the distilled water mash pH of your base malt is 5.6 then it's not surprising that 1 mL of lactic didn't get you to a lower pH. Lot of if's there and that's why you really need the meter.