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Old 05-11-2011, 07:16 AM   #1
churchy
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Default What type of PH tester

Hi guys I have been starting to get into the water chemistry side of brewing.I recently bought a RO unit and have been reading the Stickies on water profiles,and now I have a head ache.lol Anyway I want to know what type of PH tester should I get? Does temperature affect PH readings ie would I buy a PH meter with a probe and stick it in the mash or would I take a sample let it cool to room temp then measure, then I need only to buy a stick PH meter?


Cheers Andrew

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Old 05-11-2011, 11:05 AM   #2
a_potter
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Yes temp does change it alot. You should look for one with at least a +/-0.1 accuracy and automatic temp compensation (ATC).

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Old 05-11-2011, 12:04 PM   #3
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Temperature effects
1. The actual pH (nothing you can do about this)
2. The way in which the meter responds to actual pH (ATC corrects for this).

I would encourage purchase of a meter that reads to 0.05 pH or better. Accuracy of 0.1 is better than test strips but not as good as you would like for brewing applications. This level of accuracy seems to represent the difference between a $40 - 50 meter and a $70 - 80 units. And of course the more expensive ones (over $100) are good to 0.02 or 0.01.

ATC is not absolutely necessary but makes life a little easier. Without it you will have to calibrate and read samples with buffers and samples all at the same temperature or perform the temperature correction manually. A few degrees difference is OK (especially with a meter that is only accurate to 0.05). Even the under $100 meters have ATC these days.

Be sure any meter you buy is capable of 2 point (2 buffers) calibration.

All pH readings should be taken at room temperature. It is easier on the electrode and will thus result in longer electrode life and all pH readings you will see published are room temperature values. An exception to this is in forums like this one where the poster is not yet aware that this is the case or where someone has intentionally measured at higher temperature to see how much the pH changes with temperature.

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Old 05-11-2011, 12:32 PM   #4
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So when measuring the mash I should run off a sample and cool it down to room temp first? Also would I measure the PH over the whole 90min mash or just at the start and make the necasary adjustments?


Andrew

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Old 05-11-2011, 12:41 PM   #5
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I recommend sampling at 5 minutes and again at 15 minutes into the mash. The 5 min sample will tell you if you're in the ball park and the 15 min sample will be a relatively stable indicator of the mash pH. The pH does vary slightly with time, but I don't think that is a significant concern.

I use a shot glass to hold my pH sample. You don't need much wort in the glass in order to submerge the probe. Dip the glass into an ice bath and it will cool the small wort sample in less than a minute. If you pre-chill the glass, it can be almost instantaneous.

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Old 05-11-2011, 12:48 PM   #6
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I'm thinking of buying the Milwaukee sm101 on ebayusa.With the Aussie dollar so good it works out cheap.

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Old 05-11-2011, 04:12 PM   #7
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To me the biggest pain in pH measurement is calibrating the meter. Once that is done it's good for the rest of the day and measurements themselves are easy to make once you have a cooling scheme that works figured out (I use a small metal saucepan - dip it into the mash tun or kettle and then float in a couple of inches of cold water in the brewery sink).

Experience with pH readings taken at various points throughout the brewing process can serve as checkpoints for subsequent brews. Thus, IMO, you should take lots. At dough in, 10 and 20 minutes into the first rest, at the completion of each rest, coming out of lauter and and the end of the boil. Then in the fermenter every few hours and then every day or 2 and then finally in the finished beer.

There is plenty of discussion about what the initial mash pH should be. The readings beyond that lend assurance that the process is going normally. If you are used to seeing pH drop 0.15 in the kettle and it only drops 0.05 then you know something is wrong (or at least different) and should try to figure out why.

One of the most comforting applications is in checking that the fermentation is starting normally. Yeast will drop the pH of properly fermenting beer hours before any visible signs are apparent. This is especially the case if enclosed (such as cylindroconical) fermentors are being used. A drop of 0.2 pH or more in the first few hours is a pretty sure sign that a healthy fermentation is underway.

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