Occasionally, I see the posts when people ask which ingredients are their favourite ones. It made me think and I decided to write about the group of the ingredients which fascinate me.
I love fatty alcohols, their structure, how they behave and how useful they are.
For people who don’t like the word “alcohol” in it and think that alcohol will dry skin - good news. It doesn’t.
The alcohol in hand sanitiser is a tiny molecule that evaporates in seconds and takes your skin's water with it. A fatty alcohol is enormous by comparison: a long greasy chain with one small water-loving tip on the end. It comes as white waxy flakes, melts around 50 °C, and doesn't evaporate at all. It's an emollient. A lovely, solid emollient! That shape: big greasy chain, tiny tip — is exactly why it behaves so differently depending on what else is in the pot.
In lotions and creams (oil-in-water, where water is continues phase and little drops of oil inside it)
Cetearyl or cetyl alcohol is not your emulsifier, alone it can't hold oil and water together. But pair it with a real one and together they build something clever.
Liquid crystals — this is the bit worth knowing the name for. A liquid crystal is a halfway state between liquid and solid: it flows, but its molecules stay lined up in neat layers. Like a deck of cards that slides around yet never stops being a stack.
As your cream cools, the fatty alcohol and emulsifier arrange into exactly that: flat sheets stacked one on another, with water trapped between every pair. Formulators call it a lamellar (layered) liquid crystalline phase, or a gel network.
The stack makes the cream thick, oil droplets sit in a jelly rather than floating loose. And the water locked between the sheets is why a good cream feels moisturising, not greasy. Skin's own barrier is layered the same way, which is part of why these creams feel so comfortable.
Some advice: Use 3–6%, and respect the heat. Melt to 75 °C, blend, then keep stirring gently as it cools through 45–35 °C — that cool-down is when the layers assemble. Who read my post about shear and homogeniser, its where and why we swap high shear to low while cooling. Cool it fast and standing still and you get thin, gritty lotion. And don't judge thickness for 24–48 hours, it's still building.
In water-in-oil creams (where tiny drops of water wrapped inside continues oil phase)
Flip the phases and the scaffolding simply can't form! There's no water phase for it to build in. Now it's just a wax that stiffens the oil and holds the water droplets in place. Useful, but keep it low (0.5–2%) or you buy waxy drag instead of stability. A pinch of salt in the water phase does far more here. I prefer it to beeswax any time
In balms, scrubs and whipped butters (no water at all)
Same story — pure wax, no scaffolding. But it's a nice wax.
For your balms: 3–8% adds firmness without beeswax's tacky, sealing feel. Smoother melt, better slip. Lovely in the lip balms!
Whipped butters: 3–8% helps the whip hold its shape and stops it slumping in a warm room. Stearyl beats cetyl here because it melts higher (58 vs 49 °C). It also makes shea feel lighter and less greasy. It won't fix shea graininess though — that's a tempering problem, not an ingredient one.
Oil scrubs: 3–5% thickens the oil so the sugar stops sinking and the oil stops pooling on top. This is the single best fix for a separating scrub.
Try it!
Just quick picks: Cetyl = softer, lighter, silkier. Stearyl = firmer, waxier, better in heat. Cetearyl = a blend of the two, and the most forgiving of the three. Start with cetearyl.
Overdose it anywhere and you'll get the same two complaints: waxy drag, and a white smear when you rub it in. With fatty alcohols, less is usually more.
