Ever had that experience when you finally move out of your parent’s house into your own empty apartment, possibly with a roommate, and you realize there’s so much more to setting up a place than you expected? Like, yes, you obviously need the basics—couch, table, mirror—but then you realize, you also need a utensil organizer to separate your forks from your spoons, a knife sharpener so you can cut those tough vegetables, and a water filter because, well, living in California means drinking water straight from the tap is highly discouraged. It’s the little things, the ones you never really considered, the things you probably thought just appeared out of thin air or simply existed since the beginning of time. But no, each household item was thought about and intentionally chosen to make this house a functioning home (thanks mom 😊).
That’s what cosmetic formulation feels like to me, more or less.
The deeper I get into formulating, the more I realize how much I need to think about. Obviously, there are the big things like pH, temperature, solubility, viscosity, stability, efficacy, blah blah blah the list goes on. But one thing I didn’t consider as a beginner formulator?
Charge (+/-).
Yep, every ingredient in your formula has a specific charge. It’s either positive, negative, or neutral. And mixing these can be a bit tricky—especially when you’re working with ingredients that have opposite charges. If you’re not careful, your formula could end up all kinds of messed up.
Types of Charge
Back to Gen Chem 101. A quick refresher of the definitions: anionic ingredients carry a negative charge, cationic ingredients carry a positive charge. Finally, the non-ionic ingredients are the neutral crew: they don’t have a charge, which makes them compatible with both the anionic and cationic ingredients (for the most part).
So, how does this all play out in a formula?
Opposites attract! A little too much…
When anionic and cationic ingredients meet, they create something called electrostatic attraction. They bond and become pretty inseparable, which can cause them to precipitate—basically, clump together in solid particles or granules. This makes it hard for your formula to mix properly or deliver its intended benefits, reducing its efficacy. For example, if you try to mix an anionic surfactant (like a shampoo) with a cationic conditioner (like certain silicones), they’ll neutralize each other, rendering both of them pretty ineffective.
When I did a little bit of digging regarding the importance of charge in a cosmetic formulation, a lot of the times it was in the context of choosing a surfactant or an emulsifier. Depending on whether you’re making a O/W (oil in water) or a W/O (water in oil) formula, the charge of the emulsifier you choose will also change. Here’s a MakingCosmetics article that’s pretty helpful in outlining the basics of this concept.
But I noticed there isn’t much discussion about how charge affects all the other parts of a formula, like thickeners! So in this post, I want to share my experience of how I unexpectedly came across this challenge.
Formula Troubleshooting with TX Vector
I was making experimenting on a new serum with the active ingredient TX Vector. I have a blog post where I talk about this new tranexamic acid derivative, and you can read it here. When I first approached it, I was loosely following a skeleton formula provided by the supplier. The problem was, I didn’t have every ingredient they recommended, so I took some creative liberty and made my own substitutions. The formula asked for 1.0% of Tamarind Seed Gum. I did not have any on hand, so I replaced it with 0.3% of a xanthan gum (version A), a widely used thickener a lot of formulators fall back on. It was an ingredient that I was also most familiar with at the time.
Everything seemed fine at first, but once the formula settled, I noticed these tiny granules. So, I thought maybe I needed to increase the mixing speed. Or heat it for longer. But neither of those changes helped. It wasn’t the process; something was definitely off with the ingredients.
So, I added less Xanthan gum…0.1% to be exact (version B). It was a little better, but still slightly grainy when I rubbed it in. Then I thought maybe the emulsifiers weren’t doing their job, so I added more of them. Still no luck. Maybe even got worse. I ended up just throwing the third batch out mid-formulation.
I was stuck. After scratching my head for a while, I decided to email the supplier. Turns out, it was a charge issue all along! TX Vector is cationic, while xanthan gum is anionic. Even a tiny bit of an anionic ingredient like Xanthan gum can throw the formula off, causing the TX Vector to “crash” out of solution, which is what caused the gritty texture.
The solution? I switched to a non-ionic thickener. So I tried hydroxyethylcellulose (HEC), a non-ionic, water-soluble polymer derived from plant cell walls. And there it was, a smooth and stable formula! I used 1.0% HEC, which I officially called version C.
I also tried making another batch with Spinosa Gum, which is also a non-ionic thickener derived from the sap of the Acacia senegal tree (also 1.0%, version D). This, too, gave me a smooth formula! But I ended up going with hydroxyethylcellulose because it felt a little more lightweight on the skin compared to the spinosa gum.
Rule #1: Since thickeners also carry a charge (anionic, cationic, or non-ionic), choosing the right one is important to avoid unwanted interactions/precipitation in a formula!
You can really see the gritty texture of A shine through.
Final Thoughts
It’s wild how much goes into formulating, but I honestly love that I’m always learning something new. Every challenge helps me get closer to creating products that not only work better but also feel better. Oh, the fun of it all!
Sure, there’s always more to consider, but I’ve found that these limitations actually make ingredient selection a bit easier. When there are too many options, it can feel overwhelming, but narrowing things down like this helps me make clearer choices.
What do you think? Does having more factors like these to consider feel like a hassle, or does it make the process more manageable for you? I would love to know your thoughts.
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