Accurate ph for clay mask - Cosmetic Science Talk

Accurate ph for clay mask

I've had an ongoing issue measuring ph with a clay mask formulation. I understand that solids are going to pose a challenge, but did assume my readings would be consistent and somewhat accurate (not fluctuate so much during readings). The product contains Honey, Water (10%), Fuller's Earth, Glycolic, Citric, Tartaric and Lactic acids, Glyceryl Caprylate, Glycerin, Sodium Levulinate, Sodium Anisate. The ph meter has been calibrated, and even when diluted my readings are fickle. We are shooting for a ph of 3.8-4.

Any suggestions or insights would be most appreciated.

Comments

  • try another meter if you can and/or cover the beaker around the electrodes when taking measurement.
  • Try using a flat-surface probe, or one designed for high-viscosity products. General purpose electrodes don't work reliably with high-viscosity/high-solids formulations.
    Robert Zonis, Sr. Formulation Chemist, Beaumont Products "All opinions and comments expressed are my own, have no relation to Beaumont Products, are fully copyrighted, and may not be used without written permission."
  • If dilution is still causing fluctuations something hygroscopic in formula (acids) are absorbing water from the air so try dilution and covering first.I have seen this before.
  • Update: We used a 10% dilution and a new electrode. Slope was around 90, and numbers were spot-on so it appears that the electrode was the culprit. Ph turned out to be very close to our intended mark. Thank you so much for the replies - great insight and suggestions I'll keep in mind if this should come up again.
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