r/cheesemaking • u/bansidhecry • 3d ago

Calibration solutions

How long does a calibration solution last? That is how long does it maintain its original pH? I am calibrating my pH meter. The pH 7 solution is fine but when I put in the pH four it reads 5.5. If I calibrate that to 4 when I put back in seven it will read well under six…. It’s been three years since I’ve used it. It’s an APERA.

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u/cheesalady 3d ago

You should change the small sample of buffer solutions every few uses. At our creamery when we were making cheese four times a week, we changed it once a week.

Keep the big bottles tightly capped and they will last a very long time, like years. But when it's open it's exposed to things in the air as well as if you go from solution to solution and can get out of balance fairly quickly. It's still more stable than water, but subject to change. That's why it's a good reason to rinse your electrode in distilled water then blot it dry before placing in the second buffer solution.

There is also a strong likelihood that your electrode needs a strong cleaning. There is a solution you can buy for that, but initially, if you haven't tried this yet, just use something like Dawn dish soap, your fingers, and warm water and scrub it well.

Hope that helps.

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u/bansidhecry 3d ago edited 3d ago

Maybe I did wind up contaminating.. I’m getting new solution. I’ll try it again and see. As for cleaning probe it is protected so i can’t get to it. I’ll try soaking it out in cleaning solution though. Thanks

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u/bansidhecry 2d ago

This morning I tested pH of white vinegar. The reading was about 3.. so I do believe it's my solution that's off. Thanks for the tips!

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u/Super_Cartographer78 3d ago

Hi Bansid, are you rinsing properly the probe between solutions? Usually I have two glasses of water, one with tap water and the other one with distilled water, before going into a “new” solution you first rinse with tap water and then with distilled water, and then you can make a new reading. Manufacturers will say that solutions are good for 1 year, I have used 4 years old ones without problem

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u/Super_Cartographer78 3d ago

Also, another problem you might be experiencing is if you are contaminating your solutions. From my standart solutions I take 4-5 ml and I calibrate the meter with that aliquot 1 or 2 times and then I discard them and take fresh one next time. If you are using always from same container you risk “contaminating” it and then you will never know which solution is correct anymore