Just a quick post to announce that I purchased an Apera SX620 pH meter (3pt calibration). I’ll probably on occasion still use Macherey-Nagel pH strips to test some products such as ones that aren’t for the face to avoid contamination.
I purchased a meter because my favorite Vitamin C serum from Cosmetic Skin Solutions was discontinued. I decided to try Paula’s Choice C15 serum (so far so good!) because of the price, but the pH strips made the serum look much lower than the advertised pH of 3.0. I was worried it was a lot lower and would cause irritation. With the meter, it came out at 2.71, which is fine with me. Review forthcoming and I’ll also add it to my refrigeration of Vitamin C serums post.