Let me preface this by saying I am no scientist, and this guide is definitely a quick one (and based very much on personal experience). I took 12th grade chemistry, and that’s it—and that was a while ago. I did, however, convince my brilliant friend Adrian to proofread this guide, and since he’s working towards his PhD in chemistry, I’m pretty sure nothing in here is outright wrong (and it if is, it’s my fault).
One of the most important things you should consider when you’re experimenting with your various DIY projects is solubility.
There’s a pretty wide spectrum of solubility, but the main ones we’re concerned with are:
- Water Soluble (water, some botanical extracts)
- Oil Soluble (oils, butters, essential oils)
- Insoluble (clays, micas, oxides)
Most of the ingredients you use will fall into one of these categories (it is also fully possible for something to be only slightly soluble). So, before you start devising any exciting concoctions, make sure you know the solubility of each ingredient.
So, point #1 is that these categories do not mix without some coercion. Within the category you won’t have any troubles—things like body butter and lip balm (oil+oil) are super easy, all you have to do is mix everything together, and off you go!
Emulsions (Oil + Water)
When water and oil mix, we get an emulsion (like lotion or soap). For this to happen, you will generally need an emulsifier, like emulsifying wax, borax + beeswax, solubilizer, or a high pH ingredient like sodium hydroxide.
The first emulsions I made used borax and beeswax as the emulsifier. They required a 50/50 mix of oil and water, and were quite finicky. The oil and water had to be the same temperature, and I needed to use a blender to get the emulsion to hold—without that amount of vigorous blending it would separate after a day or two.
After that I branched out to Emulsifying Wax NF. If you use emulsifying wax at about 25% of your oil phase you can create lotions with much smaller oil phases, giving you a much lighter end product.
From there, I found solubilizers, which allow you to make oil in water emulsions that are still liquid. Basically, you can just mix your solubilizer of choice and some oils of your choice (often essential oils), and then you can disperse that mixture into any volume of water. There are many different kinds of solubilizers; please read this page for more information.
There are, of course, many other things that can help you create emulsions—manufacturers are releasing new emulsifiers all the time! I would be very happy to hear about your experiences with them. I haven’t had time to try everything yet (le shock).
If you leave out your emulsifier, the mixture will, most likely, eventually separate. It may take a few days, so watch it. When lotions separate you generally end up with a totally unusable puddle of water with chunks or blobs of oil in it that will have to be thrown away.
You can kind of get away without using solubilizer. The mixture will still separate, but you can give it a really vigorous shake before each use to attempt to disperse the oils into the water. To get an idea of how well it will work, think of your basic oil & vinegar dressing that’s just been shaken together—it separates on your salad pretty quickly, right? That’s about what you’ll get.
Suspensions (Insoluble compounds + oil and/or water)
When you disperse something insoluble in a mixture, and it stays dispersed, you get a suspension—think fruit pieces in jello, just at a different scale. This is what happens when you mix clay or mica into lip balm to make lipstick.
To continue with the jello metaphor—if you tried to suspend fruit pieces in a glass of water, they wouldn’t suspend particularly well. This is why, when you’re making lipsticks and other cosmetics that depend on the suspension of insoluble compounds for colour, you need to let the oils cool a bit so they have a bit of viscosity before you add the clay, mica, or oxide, otherwise they will just sink to the bottom as the mixture cools.
And, of course, particle size is very important here. Micas and oxides are quite fine powders, but clays can vary. Ensure the clay feels nice and smooth or you’ll end up with a final product that feels like it has bits of sand in it.
When combining insoluble powders with oils, you’ll find some (like oxides), have absolutely no interest in going anywhere near the water. With clays, you’ll get a paste (perfect for face masks), and then a more obvious suspension, depending on how much water you add. (The reason I don’t use water and clay to make lipsticks or lip stains is because the clay dries out when you use water, the colour changes unevenly & it cracks as it dries, and it also draws moisture out of your lips.)
Water Soluble Solids in Oil, and Vice Versa (plus larger-grain insoluble solids)
This is a great way to add a bit of exfoliation to something. When I say solids I’m talking about anything from salt and sugar to beetroot extract, coarse clay, and jojoba beads. Some are water soluble, some are oil soluble, and some are insoluble. If you cross boundaries (i.e. salt [water soluble]+ olive oil (pomace) [oil soluble]), you’ll get a gritty mixture that makes for a nice exfoliating scrub.
Here’s an example: beetroot lipstick. It sounded like a nice idea, and despite knowing better, I tried anyways, just in case. Beetroot extract is water soluble, and the lipstick base is totally oil based.
It doesn’t look too bad, right? Well… let’s try it on the skin…
This would likely work better if I infused an oil with the beetroot, strained out the powder, and then made the lipstick from there, but I would probably get more of a lip tint than a lipstick at that concentration (just a hypothesis, I haven’t tried it yet).
Ok! That’s that for my quick guide—what solubility tips do you have? If you’ve got a chemistry degree, please feel free to chime in with some expert knowledge 😉