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Testing the P.H. Level of Soap

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  • Testing the P.H. Level of Soap

    How many of you test the P.H. level of your soap? I am having the dilemma of whether to splash out on yet another piece of equipment (I guess this could be quite an important one to invest in).

    The cheapest P.H. Meter I can find is the Pen Type at £28.00 on-line by Has anyone bought one and do they work with soap OK, as they seemed to be designed to be dipped into substances.

    Loving the sunshine!


  • #2
    Can't you just buy litmus paper strips for testing PH - like we used to use in science class?
    I bought a pack so that I knew when I'd neutralised my jewellery making acids enough to be able to dispose of it safely.

    I know nothing about soap making but if you wet the soap slightly and press it against it the paper will react - I remember we tested soap in science class

    Belovedly facebook group


    • #3
      Don't bother with litmus paper it's not accurate enough - you have 3 options:
      1. pH strips ( the ones that are just for for alkaline measurements not the full spectrum such as these
      2. Phenolphthalein (if you're not used to titration forget it)
      3. pH meter - you will also need calibration buffers pH7 & pH10


      • #4
        Yes, I'd heard that litmus paper was not accurate enough.

        The P.H. pen and the P.H. strips works out to be around the same price. Are the calibration buffers a separate item or built into the pen?

        What would you personally recommend using?


        • #5
          I haven't ever measured the pH of soap but i have used both a digital pH meter and universal indicator paper for work. I think it depends what you are measuring and how accurate you need to be.

          I personally prefer the Universal indicator papers as they are so easy to use, disposable, dont require calibration, easy to store and are cheap. They can be used in liquids or if you wet the soap in a small area when its a solid that would also work. The negative is that they are not so good if you are colour blind and only really give a result to the nearest whole number.

          If you need to be quite accurate (to 1 or two decimal places) a digital meter would be better but the ones i have used only really worked well in liquids and require buffer solutions for calibration that are usually separate. These also need storage and will need replacing regularly.

          Hope thats some help,


          • #6
            The calibration buffers are a separate item you use them just to ensure that the pH meter is reading on the right side of the pH curve.
            The strips are easier to use but as Yum said they are varying shades of the same sort of colours so if you can't distinguish colour they're not easy to use.
            However when measuring pH you will need a consistent protocol, there is no point just wetting your soap and testing, make up a 1 or 5% solution and test that then when you compare soaps it will all be against the same measurement.


            • #7
              Thanks to both you for your advice - hmmm, I might just stick to the tongue test for now.