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Excuse me guys~I'm making cheese at the moment. My girls tell me the meter has been calibrated. ( don't know if it must be calibrated over and over)

The milk read: 7.9 at the start~mixed citric acid in water the mix read:2.6.

added the mix to the milk and the milk then read: 6.5.

I'm after Mozzarella, so I'm looking for about 5.3-5.5.

Added lipase, will check the pH

Added the rennet, I'll check the curd in a few~


How often do you calibrate your meter?

You only need to calibrate it when it does not read the 7 or 4 calibration solution correctly ,  I check mine a few times per make .  If it Gets to   0.05 to 0.1 out then calibrate

Remember that it needs to be the same temp as what you are trying to get a ph level of . And they can take a minute or more for the fluid in the tip to come up to temp . As it comes up to temp the ph drops , so that means first reading will be a little higher than what it will end up after the temp stabilizes .

Valley, I'm not an expert on this, but I'm pretty sure milk should never be as high as 7.9 pH. I would be checking the calibration, and/or making sure the temperature has stabilized. Something is wrong somewhere ...

Should the pH be checked at the same temperature each time?

Ideally your pH meter should have temperature compensation built into it. On my Extech, it shows the temperature reading, and you can see its pH reading change as it rises to the temperature of the milk or whey or whatever. I often press the meter into the milk or curd and hold it there for 30 seconds or so before even turning it on, so that the reading stabilizes that much more quickly.

If yours doesn't have temperature compensation, that may explain the difference in the readings. Maybe there is a chart somewhere for how to translate the pH at different temperatures?? But honestly, though I have experience only with the Extech meter that I bought, I'd think this would be such an essential requirement that any pH meter would tend to include it.

FWIW, I have a vague memory that calibration on my Extech may NOT take temperature into account, so it is supposed to be calibrated at a specific temperature -- but I am not at all sure about that. I need to go back and check the manual. But that could also be a source of error ...

Well, thanks I'll have a go at it each time I make cheese and see what I get. I'll see about getting known pH water.

"known pH water" is distilled water. That should have a pH of 7

Better yet, get some 4.0 and 7.0 buffer solutions - these are available quite inexpensively (at least in this country) via Amazon.

Those solutions are a bit dear, but, I may give in. What is ATC, is that Automatic Temperature Control? ,,,,,,,,,,,,,,,,,,,Yes, I think it is (Temperature Compensation Automatic, 0-50 C, 32-122 F.

ATC does sound like temperature compensation. On my Extech meter, it takes a bit of time for the temp to settle - as much as 30 seconds.

The cost for the buffer solutions is all over the map, but you don't need to spend a fortune on them. Here is what I have been using: https://www.amazon.com/Atlas-Scientific-Calibration-Solution-Bottles/dp/B00SCADT3K/ref=sr_1_5?ie=UTF8&qid=1476882988&sr=8-5&keywords=4.0+buffer+solution

$10 if you have Amazon Prime, or $10 plus shipping if not. Or you can pay $4 more and get twice as much (8 oz. bottles instead of 4 oz.). And better yet, they last a long, long time.

I don't calibrate every time I make cheese, but maybe every 3rd or 4th time. You only need a little bit each time, so these last a long, long time. I bought 8 oz. bottles almost two years ago (ordered them on October 29, 2014), and I still have about half of the 7.0 bottle and a third of the 4.0 -- I use the 4.0 a bit more quickly, because my Extech calls for storing the tip in a cap with a sponge soaked in 4.0 buffer solution. So I'd guess I'm going to get 3 years out of my $16 order! (Yes, it cost a bit more when I bought them, because I bought the bottles individually rather than as a set.)

Thanks for that!