Sorry, I am just seeing this post. We are traveling and I haven’t been good about checking SMF.
I do have a PH meter that my husband has used to test and adjust fertilizer. He said it seems to work well and the seedlings seem to agree. I have not yet used it for cosmetics. Unfortunately, the model I have is no longer sold on Amazon. It’s this one pH Meter, Jellas High Accuracy...
https://www.amazon.com/dp/B071V8BT5J?ref=ppx_pop_mob_ap_share. I don’t know if this link will work so here’s a picture.
I am probably going to try the DIY pourable shampoo bar recipe and will need to test that so I better check my meter when I get home.
I found a SCM post where she pictured a meter she uses. It is this one.
HM Digital PH-200 Waterproof pH Meter, 0-14.00 pH Range, 0.01 pH Resolution, +/- 0.02 pH Readout Accuracy
https://a.co/d/6wbMj7C
She also uses this one, and says is a good budget model. It’s not waterproof so if that’s a concern you may want to spend a bit more.
PH Meter with Automatic Calibration, 7Pros High Accuracy Pen Type Water Quality Tester, 6 pH Buffer Packets , Pocket Size Tool for Testing Alkalinity of Drinking, Pool and Aquarium Water, Testing Range 0.00-14.00 pH
https://a.co/d/ftheoRa
The more I read the more confused I became about how to properly use these meters. I definitely need to spend more time reading and playing around with my meter.