Hey everyone, it’s Mia here, from that cosmetic emulsification supplier you might’ve heard me ramble about at industry trade shows last month. Today I wanna talk about something we get asked literally every single day: why some face serums or moisturizers sink into your skin like they’re wearing tiny scuba gear, and others just sit on top, making you feel like you slathered a thick layer of whipped cream that never actually absorbs. Spoiler alert? It’s not magic (unfortunately, I’ve tried making a “skin penetration spell” batch that smelled like lavender and ruined three refrigerators). It all boils down to the formulation of the emulsion itself—y’know, the mix of water, oil, emulsifiers, and active stuff we spend 12 hours a day tweaking in our lab. Cosmetic Emulsification
First, let’s keep this real: I used to think “penetration” just meant “how light the product feels when you pat it on.” But nope, there’s actual skin science here, and I’ve seen clients lose big accounts because their “fast-penetrating” lotion was just sitting on the stratum corneum like a rude house guest at a dinner party. The stratum corneum is that top layer of your skin—think of it as a brick wall: dead skin cells are the bricks, and lipids (fatty stuff like ceramides, cholesterol, fatty acids) are the mortar. For a cosmetic emulsion to get past that wall, it needs to move through either the bricks (transcellular) or the mortar (intercellular), right? And every part of the formulation changes how easily it can do that.
Let’s start with the oil phase, because this is where most of the confusion happens. A lot of new brand founders think “lighter oil = better penetration” and reach for jojoba or squalane, but wait—there’s a whole science to oil polarity here. Oils are either non-polar (like mineral oil, silicone oils) or polar (like plant oils with omega-6s, rosehip seed oil). Your stratum corneum’s mortar is mostly polar lipids, right? So if your emulsion’s oil phase is too non-polar, it can’t mix with that mortar to slip in. But if it’s too big? Like, heavy castor oil with 30+ carbon atoms? It’s too bulky to wiggle between the cells. That’s why I recently worked with a clean beauty client who switched from their old emulsion’s oil blend (heavy olive oil + mineral oil) to a mix of squalane (30 carbons, but super fluid) and grapeseed oil (18 carbons, polar) and saw a 40% jump in independent lab testing for active ingredient penetration into the lower dermis. Game changer, and we didn’t even change the emulsifier—just swapped the oil ratio.
Then there’s the water phase, which I feel like no one talks about enough. The water phase isn’t just “the stuff that makes it not oily”—it also includes humectants like glycerin, hyaluronic acid, and panthenol. If your water phase has too high of a humectant concentration? Wait, that can backfire. I once had a client who crammed 2% sodium hyaluronate into their night moisturizer because they wanted “plump skin,” but the emulsion wouldn’t penetrate. Why? Because hyaluronic acid draws water to the top layer of skin first, and if there’s too much, it forms a temporary gel layer on the surface that traps the emulsion’s oil and active particles from getting in. We adjusted that client’s humectant mix to 0.5% hyaluronic acid and added a bit of propylene glycol to balance the water phase’s viscosity, and boom—their penetration rates went up. Pro tip: water phase isn’t just filler, it’s a key player in how the whole thing moves through skin.
Now the big one that’s our bread and butter as an emulsification supplier: emulsifiers. This is the stuff that holds water and oil together in an emulsion, right? There are two main types: o/w (oil in water, which is lighter, like most toners or lightweight moisturizers) and w/o (water in oil, which is thicker, like cold creams or deep moisturizing balms). But not all emulsifiers are created equal, and their HLB (hydrophilic-lipophilic balance) number is make or break here. HLB measures how much an emulsifier likes water vs. oil—low numbers mean oil-loving, high mean water-loving. If you pick an emulsifier with the wrong HLB for your oil phase? The emulsion will separate immediately, but even worse for penetration: if the emulsifier is too strong for the oil, it’ll form a super tight layer around oil and active particles that can’t slip past the stratum corneum. Let’s take an example: a client wanted a lightweight o/w sunscreen emulsion, so they picked a super high HLB emulsifier to keep it “extra light,” but that made the emulsion’s particle size way too tiny (like, under 200 nm) and the emulsifier was so tightly bound, the active UV filters couldn’t break free to penetrate the skin and actually protect it. We swapped in an emulsifier with a slightly lower HLB, upped the particle size to 300-500 nm, and suddenly the UV filters were able to shed that emulsifier shell and get into the upper layers of skin where they need to be. That’s the stuff we deal with every single day—tweaking HLB to balance stability and penetration.
Wait, let’s talk about particle size too, because that’s a direct result of emulsification (read: our job). When we make an emulsion, the size of the oil droplets (or water droplets, depending on o/w or w/o) is everything. The stratum corneum’s pores between cells are only about 500 nm to 1 micrometer wide, right? So if your emulsion’s droplets are bigger than that, they can’t fit through. I once had a client who came to us panicking because their new serum was “greasy and didn’t work” and their emulsification machine was broken. Turns out their oil droplets were over 2 micrometers—way too big to squeeze through the skin’s gaps—so they just sat on top. We adjusted the homogenization speed (faster spinning breaks droplets smaller, slower keeps them bigger) and got the droplet size down to 450 nm, and that serum went from sitting on skin to being absorbed in 2 minutes flat. Also, not just size—polydispersity (how uniform the droplets are) matters too. If you have a mix of super tiny and super big droplets, the big ones block the small ones from getting in. We always aim for a narrow particle size distribution for our clients’ emulsions, because that’s non-negotiable for penetration.
Then there are the active ingredients, which everyone cares about, but they have to fit the emulsion. If your active is, say, vitamin C, which is water-soluble, putting it in a w/o emulsion won’t do much—because it can’t get into the oil phase to move through the mortar. Same with retinol, which is oil-soluble: if you stuff it into an o/w emulsion, it’s stuck in the water phase and can’t penetrate. We had a client who wanted a retinol moisturizer that was non-greasy, so they tried putting retinol in an o/w emulsion. It looked and felt great, but when we tested penetration, less than 10% of the retinol actually got past the top layer of skin. We switched it to an o/w/o (oil-in-water-in-oil) double emulsion, which lets the retinol sit in a tiny oil core inside the water phase of the lightweight moisturizer, so it can move through the skin. That client’s product became their top seller in 6 months—all because we matched the active’s solubility to the emulsion type.
Wait, I know this can get super jargon-heavy, so let’s make it relatable. Let’s compare two popular products: a $50 drugstore face serum and a $250 luxury face serum. The drugstore one might have a great oil blend, but their emulsifier is cheap, high HLB, and their droplet size is all over the place, so the active is stuck on top. The luxury one might use a custom emulsifier blend, balance the oil and water phases perfectly, get the particle size right, so the active sinks in faster. But that doesn’t mean expensive = good—we’ve had a big luxury brand come to us because their “ultra-premium” emulsion had terrible penetration, and we fixed it by adjusting the oil blend and emulsifier, and they cut their production cost by 20% too. That’s our sweet spot as an emulsification supplier: making products that work for consumers, not just for the price tag.
Also, let’s not forget about the skin’s individual factors, right? Like, if you have dry skin, your stratum corneum has less of that lipid mortar, so the emulsion needs to be more polar and a bit thicker to slip through. If you have oily skin, your skin already has extra sebum, so a too-greasy emulsion will sit on top, so you need a lighter oil blend and smaller droplets. We work with clients to adjust emulsions for different skin types, but the core formulation rules still apply. For example, we did a batch for a sensitive skin client, so we cut out all harsh emulsifiers and used only natural HLB-balanced ones like lecithin, and adjusted the oil phase to be all squalane and jojoba (polar, small molecules) so it didn’t irritate and penetrated well, even for people with reactive skin.
Wait, I wanna bust a common myth real quick: more active ingredients = better penetration. No way. A client once added 5 actives to their moisturizer: vitamin C, retinol, niacinamide, hyaluronic acid, and ferulic acid. The emulsion couldn’t hold all of them, the particle size got all messed up, and less than 5% of any active penetrated. We cut it down to 2 actives, balanced the formulation, and penetration went up to 65%. Less is sometimes more when it comes to emulsions, because each extra active can throw off the polarity, HLB, and particle size.
At the end of the day, as an emulsification supplier, our whole job is to translate that science into something brands can make, and consumers can use. We don’t just mix stuff together—we test every batch for HLB, particle size, penetration rates, stability, and how it feels on skin. That’s why so many big and small brands come to us when their products aren’t working, because we know exactly how to tweak the formulation to get that perfect balance of light feel, good stability, and actual penetration.
If you’re a brand founder, formulation chemist, or someone who’s been struggling with an emulsion that either doesn’t absorb, separates, or doesn’t get your actives working—hit us up. We don’t do one-size-fits-all; we work with you to adjust every part of the emulsion to fit your product’s needs, whether it’s a serum, sunscreen, moisturizer, or whatever you’re making. No weird sales calls, no confusing jargon—just real talk about emulsions that actually work.
Ultrasonic Coating System References:
- Barry, B.W. (2001). Delivery of molecules into and through the skin. Journal of Controlled Release, 74(1-3), 23-33.
- Schaefer, H., & Redelmeier, T.E. (1996). Skin Barrier Function: Principles of Percutaneous Absorption. Karger Publishers.
- Rieger, J. (2010). Emulsifiers in personal care products. Cosmetics & Toiletries, 125(11), 57-68.
- Roberts, M.S., & Walters, K.A. (Eds.). (1998). Dermatological and Transdermal Delivery Systems. Marcel Dekker.
- Junginger, H.E., & Bouwstra, J.A. (2001). Lipid emulsions for improved skin penetration. Advanced Drug Delivery Reviews, 47(2-3), 109-128.
Hangzhou Precision Machinery Co., Ltd.
Hangzhou Precision Machinery Co., Ltd. is one of the most reliable manufacturers and suppliers of cosmetic emulsification machinery in China, also supports custom service. With abundant experience, we warmly welcome you to buy advanced cosmetic emulsification machinery from our factory.
Address: NO.1, 10th Rd. Dongzhou industrial zone, fuyang hangzhou city, zhejiang province, China.
E-mail: abby@jh-ultrasonic.com
WebSite: https://www.jh-ultrasonic.com/
