|Kimwipes and buffer solutions and nitrile gloves oh my!|
In This Post:
- My pH kit haul
- Prepping my gadgets
- Test results
- Lots of science blather about Vitamin C, BHA, and AHA
- Whether it's worth going to all this effort
Over the last year, my interest in beauty products has shifted; I am as enamoured of Asian beauty products as ever, but now I'm highly curious about the science of skincare.
If you've been following my blog, you may have noticed that I have started looking deeper into the ingredients of my products, especially those that are considered 'actives' and therefore expected to have reliable results, and doing a lot of research on the science of skin and skincare, such as my Skincare Discovery: Why the pH of Your Cleanser Matters post, where I get granular about why pH is so integral to the health of your skin.
However, doing science-at-home isn't easy, and some of the questions I get are how to test your products effectively at home, which pH strips to use, and how to test the pH of lipids (oils, fats, etc). The problem is, pH testing works via measuring an aqueous (i.e. water-based) solution. Spoiler alert: you can't at-home test oils, although pH testing oils is a part of fuel manufacturing. That being said, unless you are planning on refining diesel in your basement (in which case, I don't want to know) at-home oil testing is off the table with current methods.
One of the easiest and cheapest ways to pH test your products is with pH strips, and for most products, these work great. I used to have the kind that looks like a roll of tape which you tear off a piece as you need to, and then compare it to a series of whole number and then guess. I find the kind with multiple colour references on a single strip is easiest to be accurate with, although you still have to guess. I don't like guessing.
|pH strip result for my tap water. Is it pH 7? 7.25? 7.5? Who knows?? (Spoiler: my water is actually 7.55)|
Precision is less of an issue if you have something like an AHA, which is tolerant of a pH of 3-4.5 (above 4.5, you are going to lose the efficacy of exfoliation, although you may still get other benefits) so if your pH strip result looks like it's approximately pH 4, you should be fine. Maybe it's really pH 3.75 or 4.25, but 'approximately 4' is within the acceptable range.
When you get a BHA, however, that range narrows to below 4.2, so 'approximately 4' could potentially be too high. LAA (one of the popular Vitamin C serum sources) is even more sensitive, requiring a pH of less than 3.5. [source]
So while chatting with a NMR-based metabolomics research scientist (aka a lady who knows her way around pH testing fluids) and learning about limitations of pH strips when testing acids, I decided to purchase a digital pH meter at her recommendation.
The first one I bought was a bust, as the electrode was embedded inside a giant base that had to be immersed in the liquid until the electrode was covered. This is fine for dunking into an aquarium, swimming pool, or any other large body of fluid. Testing a $60 face serum, where every drop is precious? Uh, no. I'm not willing to sacrifice a third of a bottle or jar of a product for testing purposes.
|Tiny screwdriver NOT included!|
This meter is a 2 point manual calibration, which means that you have to purchase 2 specific buffering/calibration solutions (pictured at the top of this post), one of which is 'neutral' (usually 7.01) and one that is either low (4.01) or high (10.1) for the 2nd calibration point.
These solutions are tricky/expensive to buy online, so I had to go old school and call around to my local fish supply stores. After a very talking to an increasingly mystified employee there, they ordered me in the pH solutions I needed, which were less than $2 ea so I had them get me a 7.01, 4.01, and 10.1.
I am not sure what he thought I was up to, but he finally asked me flat-out what I was using it for, and when I explained it was to pH test my skincare for my blog, he became strangely excited which makes me think that he was either encouraged that girls are nerds too, relieved that I wasn't trying to cook up some sort of Fight-Club-Soap operation, or that he's just really into pH testing?
At said scientist's recommendation, I also picked up some Kimwipes and powder-free Nitrile gloves, and some distilled water for rinsing as I test. Safety first, you know!
The meter did not come with a screwdriver to adjust the Calibration screws at the top, but luckily my husband had one in his stash of electronics
I had assembled all my gear and was excited to start, when I read the instructions (pictured at left) which requires it to be soaked in pH solution for hours before initial calibration.
Cue extreme disappointment. Then I realized I had neglected to get beakers or test tubes to create the narrow container I needed, and scrambled around in my kitchen until I found a wineglass (DON'T JUDGE ME, it was all I had, ok?!) that dipped down into the stem and gave me the narrow-but-deep shape I needed. Per the instructions, I poured some of the pH 7.01 solution into the glass and soaked probe for a few hours. The calibration instructions, including how to complete the 2 point calibration is below:
I used the 4.01 solution (instead of the 10.01, which I am saving for another time) and found that it takes a long, long time for the readings to stabilize before you adjust them. I recommend making yourself a coffee, watching something on youtube, or walking your dog. It's going to be a while.
Once I had it calibrated, I went crazy testing my pH dependent products. Vitamin C serum not tested or pictured because I am out. What fascinated me about this test was that the digital results were actually lower than what my pH strip estimates were, which was a good thing.
After each test, I thoroughly rinsed the probe, dried it with Kimwipes, and stored/reset it in the 4.01 buffer solution while I cleaned and dried my other wineglass between products. I did not adjust the calibration each time I returned it to the 4.01, as I presumed I was contaminating the pH each time I double-dipped the electrode back into it, but it only went up to 4.07 by the end so I'm confident that at most it was reading my products approximately 0.06 higher than they really are.
Mizon AHA & BHA Daily Clean toner result: 4.30
This was interesting, because I had previously pH strip estimated a 4.25-4.5 range, so I was relieved to see that my estimate was accurate. As I mentioned above, that's low enough for AHA but too high for BHA. Either way, the concentration in this toner is too low for use as a deliberate chemical exfoliation, but that's not what it's used for. It's great as a pH adjuster for the skin; when using pH dependent products your skin needs to be at a natural/low pH before use, so you can either let your skin self-adjust after cleansing by waiting 15 minutes, or you can force the pH down with a product if you are rushed/live in a dry climate. This toner is excellent at the latter. That's how I use it, as well as cleaning off the post-acid-exfoliation sludge of dissolved dead skin and sebum before applying the rest of my products.
Cosrx BHA Blackhead Power Liquid results: 3.37
My original pH strip estimate was 3.5ish, which was fine for a BHA but I am pleased to see that this landed between 3-3.5 which is right in the 'butter zone' for BHA. If you use BHA and AHA in the same routine, your BHA will be first for two reasons: 1. it has a lower pH dependency than AHA, and 2. BHA is oil-soluble so it can get down-n-dirty into your sebum-choked pores and do its battles there. This clears the way for AHA, which is not oil soluble and thus would otherwise have its efficacy reduced.
Mizon AHA 8% Peeling Serum result: 3.89
My pH strip estimation for this one was 4, so still close but I'm relieved to see it's in the 3.5-4 range. However, since it is over 3.5, I don't layer it over my BHA to avoid disrupting the pH zone it's working in (which is best below 3.5) and wait 20 min after BHA before applying my AHA serum. I then wait another 20 min to let the AHA do its thing, and then carry on with the rest of my products.
Will I break this out to test every new product? Honestly no, because it's a pain in the ass and requires recalibration each time you take it out of storage; it's stored with solution in the cap (pictured in the image with the screwdriver) to keep the probe from drying off, but it still needs to be rechecked for accuracy (and adjusted if need be) before use. That means keeping plenty of the buffering solution on hand as well.
The results showed me that my pH strips + eyeball estimates are close enough for non-pH dependent products like serums, essences, cleansers, etc. So for 80% of my products, the strips are fine.
However, if I am testing pH dependent products that have specific pH requirements, I will definitely break out this kit and get all Mad Scientist in my kitchen.
All the best,