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Old 11-01-2010, 03:03 AM   #1
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Default Proper use of a pH meter

I've seen a lot of posts about pH meters but have not seen any that specifically describe how to use it on brew day.

I've been sticking the meter directly into the mash...and I'm starting to think this is a bad idea, and hoping that I haven't damaged the meter.

I've seen a couple of people mention that they cool a sample of wort to room temperature and then measure that. How do you cool it? Seems like time is of the essence in measuring and adjusting the pH. If you have to make several adjustments and each time you measure the pH (to measure the effect of the adjustment), you have to wait for a sample to cool to room temperature...isn't that a lot of valuable time? Time in which the majority of the starch conversion has taken place?

Same basic question for measuring the sparge/runoff. How do most people do this? Collect a sample of the runoff in a glass and cool it to room temp?

Any tips/insights would be appreciated!

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Old 11-01-2010, 03:17 AM   #2
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If you have been dunking your electrode into hot mash you have stressed it but not destroyed it. It's lifetime will be shorter than it would be if you had cooled all samples but if you measure cool samples from now on it will last longer than if you keep measuring hot ones.

There are lots of ways to cool samples. I have a very small metal pot (miniature version of a standard cooking pot) that I use to dip a sample of mash. This I put into a sink with a bit of cold water in it and swirl this around until the mash is cool. With the good heat conductivity of the metal this happens pretty quickly but there is some time delay. One way to solve this problem is to do mash pH measurement on a test mash i.e. a small portion of the grist you intend to use doughed in with the water you intend to use. That should get you into the ballpark WRT acid, sauermalz or chalk additions so that on brewday what you are doing is checking, not designing the beer as you go.

For runoff I collect into a hydrometer jar which then gets set into a pitcher of cold (tap running) water. Such samples cool pretty quicky but again there is some time delay. When the sample is cool the hydrometer is inserted followed by the pH electrode. With a little experience you will know at what °P you should terminate collection and not have to bother with the pH check.

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Old 11-01-2010, 02:26 PM   #3
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I have a little plastic vial I saved from something. I put the sample in there and place in a bowl of ice water. It cools in just a few minutes.

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Old 11-01-2010, 03:42 PM   #4
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Similar process here, sample in a shot glass then chilled in a bowl of ice water. Takes a few minutes. It's also better to take a reading at the temp you calibrated the meter so you don't have to convert for the pH drift due to temp.

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Old 11-01-2010, 03:49 PM   #5
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The reason for measuring at the same temperature as the calibration is that it puts less of a burden on the ATC algorithm. Should the electrode have an isoelectric pH (the pH at which it is insensitive to temperature change) outside the interval 7±0.5 pH the ATC algorithm doesn't work as well as it can. The errors this causes are usually not significant so you probably don't need to worry about this as nearly all electrodes meet this spec (though I happen to have one that doesn't).

The shift in actual pH is an entirely different thing. ATC is compensating for the change in the electrode's response with temperature. The shift in pH with temperature has nothing to do with the electrode. It will be there no matter how you measure pH and there is really nothing you can do about it. It is best to record pH and temperature both so that you can apply "english" to your measurements if they are at other than a standard temperature. As noted above room temperature is best in terms of stress on the electrode.

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Old 11-02-2010, 03:31 PM   #6
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Quote:
Originally Posted by ajdelange View Post
One way to solve this problem is to do mash pH measurement on a test mash i.e. a small portion of the grist you intend to use doughed in with the water you intend to use. That should get you into the ballpark WRT acid, sauermalz or chalk additions so that on brewday what you are doing is checking, not designing the beer as you go.
Solid advice as usual...thanks. Hey, I'm using your baseline/primer for my next batch. I know you're not psychic but based on your experience will the following proportions get me in the ballpark pH range: 9lb 2-row, 1.5lb cara-pils, .22lb sauermalz (roughly 2% of grain bill as per your advice). Water = DI + 1tsp CaCl2 per 5 gallon (as per your primer advice).

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For runoff I collect into a hydrometer jar...With a little experience you will know at what °P you should terminate collection and not have to bother with the pH check.
Any general advice on what °P to stop runoff, or does this vary with the beer? Maybe it's better to stop at a target pH instead? If so...what am I looking for (pH-wise) as a stopping point for the runoff?
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Old 11-02-2010, 05:06 PM   #7
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Quote:
Originally Posted by EvilBrewer View Post
Solid advice as usual...thanks. Hey, I'm using your baseline/primer for my next batch. I know you're not psychic but based on your experience will the following proportions get me in the ballpark pH range: 9lb 2-row, 1.5lb cara-pils, .22lb sauermalz (roughly 2% of grain bill as per your advice). Water = DI + 1tsp CaCl2 per 5 gallon (as per your primer advice).
It should.


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Originally Posted by EvilBrewer View Post
Any general advice on what °P to stop runoff, or does this vary with the beer? Maybe it's better to stop at a target pH instead? If so...what am I looking for (pH-wise) as a stopping point for the runoff?
I think it depends more on equipment than the particular style. I always advocate measuring pH and gravity. If the pH is still below 6 when you hit, say, 4°P then I think you can use the gravity reading to terminate collections.
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Old 11-02-2010, 05:22 PM   #8
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Quote:
Originally Posted by ajdelange View Post
I think it depends more on equipment than the particular style. I always advocate measuring pH and gravity. If the pH is still below 5 when you hit, say, 4°P then I think you can use the gravity reading to terminate collections.
Did you mean pH is still below 6 by any chance? I'm reading in other places to stop before pH gets higher than 6, or when the gravity hits 1.010 (3°P)
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Old 11-02-2010, 06:36 PM   #9
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Quote:
Originally Posted by EvilBrewer View Post
Did you mean pH is still below 6 by any chance? I'm reading in other places to stop before pH gets higher than 6, or when the gravity hits 1.010 (3°P)
Yes, I did - thanks.

It's whatever you are comfortable with on the gravity. If you want every last bit of extract then you will go as low as you can but remember that at 4 °P each additional liter collected would contain only 40 grams of extract (an Oz and a half or so).
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Old 11-19-2010, 02:04 PM   #10
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Hi, AJ,

I used your primer for a recent batch of an APA:
- 9lb American 2-row
- 1.5lb cara-pils
- 0.22lb sauermalz (roughly 2% of grain bill as per your advice)
- 1.25 oz Cascade (60min)
- 1.75 oz Cascade (1min)
- 1056 yeast w/starter
- 1 tsp CaCl2 per 5 gallons
- 1/4 tsp CaSO4 per 5 gallons

This actually overshot the acidity a bit. The mash pH was around 4.8. No worries...I will reduce the sauermalz next time.

I tried to add some baking soda to bring it up, but I guess I didn't add enough and I was a little afraid of completely ruining the batch (that, on top of the fact that time was ticking away and by the time I'd cooled the third mash sample to room temp, it was like 15 minutes into the mash)...so I just figured I'd run with what I had. And that was a pretty solid 4.8 throughout the mash.

Everything else on brew day went pretty well. Vourlauf'ed (sp?) for about 20 minutes using my March pump. Fly sparged; grain bed never exceeded 168-ish. 60 minute boil. Cooled with CF chiller. Pitched yeast and saw activity within 12 hours.

I fermented at 66F for about 10 days and then crash cooled to 35F once there was zero activity in the airlock. I didn't rack to secondary, as I've been trying out Palmer's/Zainasheff's advice of doing the whole fermentation in my primary.

Anyway...tasted some hydrometer samples yesterday and they're pretty good. Definitely not as harshly bitter as my previous batches (in which sulfates were MUCH higher). But there is definitely a grainy taste. And there is still this kind of cloudiness in the taste. I know that's vague...but it's like the malt and hops are somehow muted. Maybe I just need to be patient and let it age?

I guess my question is this: could these factors be a result of the lower than optimal pH??

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