Go ahead, make a Fight Club joke. I know you want to. Oh, wait, you can’t, or you’ll break the first rule of Fight Club and Brad Pitt will hunt you down and make you eat that bar of pink soap he’s always holding. (I realize some of you would probably like Brad Pitt to hunt you down, but let’s move on, shall we? I’m sure he has better things to do than make you eat cleaning products.) So—homemade soap. Why? It’s not like store bought soap is the most expensive thing on your grocery list by a long shot, and you probably only buy a bar a couple times a year. So why bother to make your own? Well, for starters, it’s pretty freaking fun, especially if you’re a DIY-type. And, even if you do end up buying a bunch of new ingredients for your soap-making endeavors, almost everything but the lye can be used for other body-care things. And the lye can be used to clear drains. Or start your very own fight club (shhhhhh).
Second reason—there’s a lot of suspicious stuff in mass-produced soap. The fragrances are almost always entirely synthetic, and even the “unscented” stuff has fragrance in it to cover up the scent of the plain soap (makes me wonder what kind of wizardly goes into “unflavored” stuff…). The oils used are usually just whatever’s cheapest, so beef tallow, palm oil, and coconut oil are very common ingredients. These oils make a bar that is hard and has a nice lather, but it won’t be very moisturizing. And, both palm and palm kernel oil are environmentally controversial right now as they are often harvested by destroying Orangutan habitat.
There are countless other reasons that natural soap is better for you and the environment than the mass-produced stuff, but I’m climb down off my soapbox (haha, couldn’t resist) and get to the chemistry part of things now!
Soap is made by combining a variety of oils with a lye (sodium hydroxide) solution. Each type of fat requires a different quantity of lye to convert it into soap, so most people (myself included) use a lye calculator (my favourite is Soap Calc—and here’s a video on how to use it) to figure out how much lye and water they’ll need for a given amount of any given recipe.
As far as choosing fats for your soap go, there are 3.5 different categories of fats, and you generally want one from each to make a nice bar. First, there are the hard fats (tallow, lard, and palm), which will help firm up your bar so it doesn’t melt into a lump of goo when it gets wet. Second, you have the lathering oils, which are pretty much coconut and palm kernel. Third, you want the soap to be moisturizing, but not ridiculously expensive to make, so something like olive, canola, or sunflower will do. The half category is for castor oil (USA / Canada), which is a nice double-whammy with both moisturizing and lathering love to contribute, generally at a 5–8% level. You can also create another category of more expensive, luxury oils like jojoba if you so desire. If you’re interested in learning more about the properties of different oils in soap making, there’s an in-depth article here.
You will likely want a separate set of pots and spoons for soap-making to avoid cross-contamination. I definitely recommend hitting up Value Village or whatever your local op-shop is for some super-cheap used stuff.
Alright? Ready to get started? Rad! I’ll be making a 500g batch, but you can enter any final weight you want into the calculator (no less than a pound), using the percentages in the recipe for easy-peasy scaling.
Essential oil(s) of choice; 30g essential oils per 500g of oils (1oz essential oils per pound of oils)
Equipment—anything plastic should be dishwasher safe, and nothing metal can be aluminum
- Digital scale with tare function with a capacity of at least 5kg/11lbs (you’ll be measuring everything by weight)
- Heavy-bottomed pot
- 2L juice jug
- Ceramic mug or small glass bowl to measure essential oils into
- Empty plastic container with a lid to measure lye into (I use an old cream cheese spread container)
- Sturdy silicone spatula
- An extra bowl or glass measuring cup with a spout, for mixing up multiple colours
- Immersion blender (My Braun one is still going strong after 5+ years)
- 2x instant read thermometers that start at 100°F or lower
- Something to mould your soap in; you can buy specific moulds or a loaf tin will work (silicone bakeware is fantastic)
- Parchment paper (Not wax paper! The wax will melt and fuse the paper to your soap.)
- Safety gear: Goggles, rubber gloves, & lab coat
- Spray bottle of white vinegar for any lye spills
Ready your mould. If it’s a square mould, you’ll be able to line it with parchment paper (with overhang for easy removal) without much trouble. If you’re using a mould like mine, I find using rubber bands around the end to hold the paper down works really well (since tape tends not to stick to parchment). For cake tins and other things with a semi-irregular shape, line it with plastic wrap first, and then with parchment paper.
Measure your oils (by weight!) out into your soaping pot, attach a thermometer, and place over low heat to start melting. While that’s happening, measure the essential oil into the ceramic mug. Measure the distilled water into the juice jug. Check on your oils and make sure they’re still melting. If they’re all melted, take them off the heat and get them cooling down. Do not let your oils overheat of you can get a nasty, super-hot mess on your hand.
Next up, bringing lye into the equation. Put on your safety gear. Lye has the potential to be dangerous (similar to bleach), so treat it with a healthy dose of respect. Measure the dry lye into your little plastic container, and in a well-ventilated area, add it to the water. Never, ever, EVER do this the other way around, or you will have a caustic lye volcano on your hands. Stir the solution with your second thermometer, taking care not to inhale the fumes. The lye will cause the water to heat up quite a bit, and that steam that is coming off will smell foul and make you feel pretty icky if you inhale it.
The next part is pretty boring. You have to wait for the oils and the lye to reach the same temperature, ideally somewhere around 100º–110º Fahrenheit. They don’t have to be exactly the same, but they should be within three or four degrees. You might have to do a bit of juggling to get things to match. For the oils, they can be reheated on the stove, or cooled by placing the pot in an ice water bath. Ideally, you’ll be fiddling with the oils, not the lye, but if the lye needs to be warmed a bit, place it in a hot water bath.
Once the oils are at the same temperature, pour the lye solution into the oils. Now, we stir. Using the immersion blender in short bursts, you’re looking for the mixture to be fully emulsified. About.com has a handy video that will help you figure out what you’re looking for. Once you’ve reached trace, you can stir in the essential oils.
How thick of a trace you take your soap to depends on what you plan on doing with it. If you’re just pouring it into a mould, it doesn’t have to be thick at all. If you want to suspend something in it, you’ll have to take it to a thickness that will be able to hold up your dried flowers or whatever. If you want to do swirls or layers, it will have to be thick enough that the different colours won’t just combine, like pouring milk into coffee. You’ll be looking for a trace as thick as good, cold pudding for those sorts of things.
If you’re not going to do anything special, it’s time to mould. Pour the soap into your mould, cover, and insulate with an old towel. Make sure you leave the mould somewhere it won’t be disturbed for 24 hours.
Cleaning up… urg. You can either do it straight away, still wearing your safety gear. Or, you can wait a day or two until all the leftovers have turned into soap.
After 24 hours your soap should be firm enough to cut. Using the parchment paper overhang, pull the soap out of the mould. Slice it into soap-sized bars. You can roll any trimmings into little balls, which you can use as-is or suspend in another batch of soap.
Now you wait. Place the bars somewhere cool and dry, where they’ll get decent air circulation, and wait for at least three weeks to let extra moisture evaporate out. The longer the cure time, the harder the bar will be, and the longer it will last once you start using it. This also gives the scent a chance to mellow out. Some scents last better than others, but they’ll all fade a bit.
Don’t want to fuss with all that temperature juggling?
Try soaping at room temperature—it’s basically all I do anymore (I chat about it in my Cinnamon Swirl Shampoo Recipe). It takes a bit of thinking ahead, but gives you more time to work with the soap batter as it won’t thicken up as quickly. You also don’t need any thermometers, so you can save a few bucks there.
Got all that? Here’s some extended reading!
Why there is no such thing as making soap without lye and Why I use lard & beef tallow in my soap and why you should, too, and my All in One Soap Recipe.
This entry was updated June 1, 2016.