Finally! My Extech pH110 pH meter has arrived! I ordered it last week from Lotioncrafter, but they are out in Washington (USA) and I am way over in Michigan (USA) so it took a while.
Of course, with a new toy, I had to play!
So I got out a few of my recent lotions and started measuring the pH. First I calibrated the meter, and then was off to the races!
Most of the lotions turned out pretty much as I expected (between 4.5 to 5.9), but I did have a couple of surprises.
The one I thought would be more acidic (Mello Mello Limoncello) because it has lemon essential oil in it — that one was a pH 5.25. I was expecting it to be in the “4’s”. It could be because that one also has some cosmeceuticals in it, and those can raise the pH, so maybe the lemon essential oil actually did offset that and lowered the pH after all.
The two that I thought would be the best for the skin turned out around pH 7. What is surprising to me is that other than some oils, emulsifier, water and glycerin, there really was not anything else in there to raise the pH. There was no fragrance, no cosmeceuticals and not even any extracts.
You might think, “But pH 7 is neutral, so that should be very gentle on the skin”. You would be right in that pH 7 is considered neutral. However, skin is slightly acidic, so pH 7 is actually more alkaline than the skin is.
While a pH of 7 won’t burn or otherwise injure the skin, it could upset the balance of the acid mantle. Most lotions should be in the 4.5 to 6 range.
So now I have to figure out why those two are so alkaline. Sure, I could make the recipe again and add a smidgen of citric acid to lower the pH, but I really want to know why it is so high in the first place so when I use that ingredient again, I can make the proper adjustments.
I posted a question on this to the “Making Skincare” group on Facebook and will share their answer. I thought it would be best to ask the experts. The one good thing about science is there is always a “cause and effect” so somebody will likely know what caused it.
I found that for the lotions, you can just squirt some lotion into a shot glass and measure the pH directly. I tried it this way, and also when mixed with distilled water and got similar readings, so no need for the extra step.
With creams, however, it did work better to mix the cream with a little distilled water and thin it out first before measuring.
This meter was not cheap (I bought the deluxe kit which comes with accessories) – it was $119.95 USD, but I bought it because it has an enclosed electrode. Many of the others I looked at had an exposed glass bulb electrode and it looked like it would be difficult to clean in between uses. This one is totally enclosed, so you just rinse it off, wipe it and then move on to measuring the next thing.
This meter also has a refillable electrode, so when it runs dry, you just refill it. They give you a little tool you use to open it up and add more solution.
It was very easy to get up and running. Calibration was a breeze and using it is intuitive. It’s pretty much “point and shoot”.
I also bought a new micro-scale for measuring very small amounts of ingredients. I was having a little difficulty with my kitchen scale while making lotions because some of the ingredients are measured in such small amounts, they just wouldn’t register. My new micro-scale measures down to 0.1 grams. That should do the trick!
I may have bought a couple of beakers too. 🙂 Because what is a science lab without beakers? Next up? Test Tubes? Microscope? Pointy glasses? Pocket protector?
So excited! No more pH test strips for me (well, unless I am testing cold process soap).
I posted my question on the Making Skincare group on Facebook to find out why the pH on two of my lotions was hovering around 7 instead of lower (4 to 6) and my suspicion was validated, but I also learned something new. What a great group they are! Very knowledgeable!
The lotions in question are just simple lotions with no fancy ingredients in them. Literally they are oils, water, emulsifying waxes and preservative. All these ingredients have a neutral pH (around 7), except for maybe the distilled water (mine registers at about 6).
Anyhow, since this is a simple recipe with nothing to alter the pH, naturally, the lotion is a neutral as the ingredients it contains. I suspected this to be the case.
pH 7 is nothing to be concerned about. The lotion is a gentle as putting water on your skin. But most of us have a slightly lower pH than that, so I am trying to formulate a little lower. The closer to the skin’s natural pH, the better. My skin seems to like it somewhere between 4.7 and 5.5. My husband’s skin likes it a little higher (5 to 7). Children, however, can have a higher pH, so this lotion would be great for them.
What I learned new – The pH of distilled water can change over time. It reacts with the carbon dioxide in the air and the pH drops to lower than 7. I had used the last bit of distilled water in my water jug to make those two lotions. That means it was not very fresh and had changed pH. Ordinarily, this would not be an issue for me because I usually go through a gallon of distilled water per month (at least), but around that time I had run out and had to borrow my husband’s bottle until I could get to the store. Who knows how long that has been hanging around for! But this was not the problem of my lotion. If anything, it helped reduce the pH of the lotion rather than making it high.
What else I learned – I compared these recipes with some other lotions I made that tested much lower (4.6 to 6) and those recipes had aloe vera in them. Aloe Vera juice has a variable pH (depending on where you buy it from, and they batch number), but it is generally from 4 to 5. So in those recipes, my lotion’s pH was lower as well. This is partially because the aloe vera juice contains preservatives such as citric acid and sodium benzoate and those are acidic.
Therefore if A+B=C – if you want to formulate for a slightly acidic skin type, use aloe vera juice! (You can also add small amounts of citric acid into the cool down phase to help).
Unfortunately, the only way to be able to predict an outcome is to make the recipe again, make one adjustment, test again, and see the result. Then keep repeating until you get a formula that meets your requirements. You can’t easily change a lotion once it has been made, but if you formulate in small batches until you get your recipe perfect, you can afford a few mis-steps.
I consider these lotions a success though (and not a mis-step). It was never a “problem” per se, that these have a 7.0 pH. It is just a preference I have for making them slightly more acidic than that. Most store brand lotions are formulated for certain pH levels (5.5 being a popular one). Cetaphil is 4.7 (which is why my skin likes it). Oh and by the way, before I forget, I tested my Cetaphil dupe recipe and guess what? It’s 4.7! Hooray! I guess it is a good dupe!
I just wanted to share what I learned about this, so the article is complete. 🙂