In my previous post, I described how to render fat to make lard. In this post, I will show you how turn that lard into homemade lye soap (cold process) that’s better than anything you’ll ever buy in the store.
Before I begin, I should note that this post has lots of information. Don’t let this intimidate you! If you can make a cake or brownies from scratch, I promise that you can make soap. It’s really as simple as adding three ingredients together and mixing, and pouring them into a
pan soap mold. You don’t even need to turn on the oven!
To make soap, you need:
- lye (sodium hydroxide, often sold as drain cleaner)
- water at room temperature
- fat/oil of your choice; the quantity will depend on which kind(s) you use
- very large heatproof mixing bowl (mine is 5 liters, which I think is a great size)
- good rubber gloves and eye protection
- immersion thermometer
- scale to weigh ingredients precisely (it is more accurate to measure by weight than volume, and accuracy counts here)
- stick blender
- soap mold or quart-sized cardboard milk/cream containers, rinsed and dried
- chef’s knife or pastry scraper to cut soap into bars
- additional ingredients as desired – essential oil, colorants, texturizing ingredients (oatmeal, etc.)
I didn’t list how much lye, water or fat you need. That’s because you must calculate your water and lye quantities (as well as the amount of fat) based on which fats you plan to use, and how much you want to make. Usually that requires referring to a chart and using math, but to make it a whole lot easier, there’s a fantastic spreadsheet you can download that does all the calculations for you. (Thanks to my friend Russ for finding that link!).
Steps to making soap:
- Gather all of your ingredients and equipment together. The soap-making process is relatively quick so time can matter.
- Don your safety equipment.
- Weigh your fat(s) of choice and bring it to around 150° on the stove, on low heat. Watch it carefully so it doesn’t get too hot (it takes a while to cool, which can be a problem) or worse, hit the smoke point and burn.
- Weigh room-temperature water and add to bowl.
- Weigh lye and add to water; stir with heat-proof utensil briefly and then step away. (Don’t worry, it won’t bubble up or anything. You just don’t want to breathe the fumes.)
- Wait about 3 minutes, then check temperature of lye mixture as well as the temperature of the fat. If lye is still too hot, give it a couple more minutes to cool further, until both are roughly the same temperature.
- Add fat to lye/water mixture and blend with stick blender.
You’ll note that it starts off roughly the consistency of milk, but within a few minutes it will “trace”, becoming slightly thicker and sticking to the side of the bowl, like a soft pudding. The process is kind of like whipping egg whites or cream, albeit more subtle…. everything is soupy and liquid one moment, and then the magic moment of “trace” happens.
- At trace, add your additional ingredients (fragrance oils, solids, whatever) and blend briefly to incorporate.
- Working quickly, before soap thickens too much, pour into soap mold. (If you’re using a cream container, place it in a bowl first to catch spillage so you can pour it on the top).
- Place mold somewhere it will not be disturbed for 24-48 hours. Some directions call for it to be wrapped to stay warm but in my experience that’s not necessary. It will remain warm to the touch for a while, and as the saponification process happens, it will remain rather caustic, so DON’T TOUCH.
- In 24 hours the soap will still be a little soft to the touch but will have mostly solidified. This is when you should remove it (carefully) from the soap mold, or peel away cardboard, and then slice into bars. I use a chef’s knife. While it is technically safe to use after 48 hours, you should resist the temptation and allow it to cure for two to four weeks.
With the batch I just made, I used the following “recipe”:
- 24.3 oz lard
- 5.5 oz olive oil
- 6 oz additional olive oil for superfatting (see below)
- 4 oz lye
- 9.9 oz water
These figures came from the above soap-making spreadsheet, and should yield 41.2 oz after cure. As I discovered, my previous batch, which measured 37.7 oz total weight after cure, was just the right amount for one quart carton. This time I ended up with overflow. I also used both lard and olive oil, though this is not necessary. I mainly added olive oil because I didn’t want to use part of a second jar of lard for this batch!
Stats from this batch:
- Water temperature before lye was added: 75°
- Water temperature immediately upon adding lye: 205°
- Six minutes later the water dropped to 152°, which was the temperature of the fat on the stove (on low). Time to make soap!
- Time to reach trace: 4 minutes.
- Superfatting percentage: 18% (super high)
What is “superfatting” and why should I care?
First of all, when you are making lye soap, you are creating a chemical reaction between the lye, water and fat. It’s important that you have the correct proportion of ingredients or all of the lye may not bind with fat molecules, and you will then have incredibly harsh, potentially caustic soap. Superfatting allows you to have a little wiggle room. It also gives the soap a richer, more emollient feel. Most soapmakers recommend about 5% superfatting, but experiment and see what works for you.
Important cautionary note:
Making soap is easy, but it can be dangerous. Be sure to follow all of the rules below:
- Lye is an extremely caustic and dangerous substance. Don’t freak out about using it, but do handle it with care and intelligence.
- Use a large (and ideally, metal) bowl for mixing your soap. You do not want it to splash out as the mixture is quite caustic and will burn. My regular mixing bowl wasn’t big enough so I purchased a new set of stainless bowls for this process.
- Make sure your lye/water mixture and fat are the same temperature (within a few degrees is fine) when mixing them together.
- Always add the lye to the water, not the other way around.
- Always use use gloves and eye protection (at least eyeglasses) when dealing with lye. Really, I’m not kidding. Do it. My father got lye in his eye once, and I’ll never forget his howl of pain and fear when it happened (he recovered, but he was lucky). And you don’t want the lye or the fat/lye mixture to get on your skin.
- Along those lines: do not inhale the fumes/smoke that rises when you add the lye to the water. It can burn your sinuses. You should also vent the room with an open window, stove fan, etc.
- Make sure small children and pets stay far away from the process. This is not a project for small fingers or curious critters.
Wikipedia has a nice article about the history of soap and what actually is happening in the soap-making process.