Reading pH strip tests

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Garden Gives Me Joy

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Jan 25, 2020
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United States
I have been noticing that pH strips could start out one color and then after several hours ie after the strips have dried, change in color to the extent that I might have interpreted the results differently if I observed the results at only one of the 2 times.

My process is that I put several drops of the test liquid into a dish, put the strip into the dish, lean the dish on an angle so that excess liquid can run off the surface of the strip and allow the strip to dry. If my process is wrong, what should I do differently please?

If my process is fine, should I use my observation immediately after the strip makes contact and is completely saturated ... or should I wait until the strip is dry?

Both of the images I have included here were taken on the same day, 8 hours apart. The image of the darker looking result was taken immediately after the strip was introduced to the soap water. The lighter colored version was taken 8 hours afterwards. Very happy for your comments, experiences, suggestions, etc.

What pH would you arrive at in this situation?

pH strip - 1800 hrs, 6 Jul 2023.jpeg



  • pH strip - 1100 hrs, 6 Jul 2023.jpeg
    pH strip - 1100 hrs, 6 Jul 2023.jpeg
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Feb 20, 2013
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None of the pH test strips I've ever used say to let the strip dry before determining the pH. Test strips are always evaluated shortly after they're wetted, but whether the evaluation is done immediately after wetting or after 60 seconds after wetting or after some other (short) period of time depends on the product.

When using pH test strips, read and follow the directions to the letter -- don't second-guess the manufacturer's instructions. If the directions aren't on the package, go to the manufacturer's website and find the directions there.

Even if you follow the directions, testing soap with pH test strips is not accurate. And the 0-14 unit paper test strips are the worst of the worst choice.

You really need a test strip that reads to 0.1 pH unit to get any kind of useful info about soap. Even the best pH test strips only test to 0.5 pH unit in the alkaline pH range that soap has.

Even if these 0-14 strips are able to give an accurate pH reading in soap (which they are not), they aren't remotely precise enough to tell you anything useful about your soap.

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