Easy Homemade Castile Soap from Lye
This project began because there are a lot of little hands to wash in our house which means going through soap like it’s chocolate.
Our local co-op sells Dr. Bronners in “bulk” but it comes out of the same one gallon container you can buy from Amazon. As with many large family things, you might as well get the big giant container. So I bought a gallon of Dr. Bronner’s Soap.
They have a solid reputation as an eco-friendly company, however, at $60 a gallon their soap is super expensive. They say you can dilute it, but liquid castile soap already has a watery consistency (though it lathers beautifully) and I never thought that diluting it was a great soap using experience.
When I started noticing the endless supply of baby soap containers making their way into our recycling bin, I read up on soap making. It seemed like it would be relatively straight forward, but the big stumbling block for people is lye – a fundamental ingredient of soap.
Lye makes a lot of people nervous. If it gets in your eyes it can blind you or it can burn your skin or kill you if you eat it, but other than that it’s relatively harmless.
What about lye-free soap?
Soap has to contain lye or it’s not soap. People post lye-free recipes online, which usually say something like, “grate a bar of soap, add glycerin, etc.” Lye is integral to saponification, which is the chemical reaction between lye and fat that creates soap. Claiming you can make lye-free soap is like saying you can drink oxygen-free water.
As I was reading, I came across this blog post from Northwest Edibles which contains some of the most thorough instructions I’ve ever seen. It empowered me to try my hand at liquid soap-making.
I already had olive oil and coconut oil, but did not have any lye laying around so I ordered some from Amazon. It’s important to note that there are two types of lye – sodium hydroxide for bar soap and potassium hydroxide for liquid soap.. On the day it came the heavens parted and angels started singing. Also, we were home for most of the day.
I immediately started pulling out my stainless steel things as my husband followed me around expressing his concerns about lye and the various eyes it can blind. I figured he was volunteering. He’s a chemical engineer and as he donned his safety goggles, fireworks of chemistry excitement ignited in his brain. The lye/water/saponification experience was for sure the highlight of his day. Also mine. If you never do anything else in your life, make soap. I almost wanted to switch my major to chemistry.
He couldn’t find the weedwacking goggles so he put on some swimming goggles, only to realize they were kid-sized. He decided to find my post-LASIK goggles instead. Sexy.
I did not buy any special equipment for this project. Rather than using a special crockpot (mine was coated with something), I used my stainless steel stock pot on the stove. I had a stainless steel metal spoon I used. I do not own a stick blender, so I just used my hand mixer (which worked fine). We already owned safety goggles, gloves my husband didn’t use (rebel!) and a digital scale. We used tap water because we knew from our hydroponics system that our water was pH neutral. Which is just to say that you can be a minimalist about this.
The first step is to mix the potassium hydroxide with water. No matter the temperature of the water, the reaction will make it boil.
Then you mix the lye-water solution with melted coconut oil and olive oil (here’s the recipe again).
You then mix it, mix it some more, and then let it cook for hours stirring occasionally. I found the stove top version to be much much quicker than a crock pot. Instead of 30 minutes, the soap was too thick to mix in 10. This did not seem to interfere with the process in any way – it just sped it up.
My husband grabbed my camera and started snapping goggle pictures of me as retribution. I was trying not to get splattered with boiling lye.
It turns from milky to an icing texture to partially translucent in 10 minutes.
Once it’s at the fully translucent stage a few hours later, you dilute it and it makes a fantastic liquid soap that is equal to or better than Dr. Bronners.
So back to the zero waste thing.
Why make your own soap?
My two main motivators were saving money and reducing our consumption of single use plastic.
Who doesn’t love new ways to save money? This surprised me – I definitely did not think the cost difference would be so substantial.
- Cheap Liquid Soap: $33 a gallon. If you buy cheap liquid soap (or baby shampoo) with lots of plastic this is the cost for eight bottles (about 1 gallon).
- Dr. Bronner’s Soap $60 a gallon, depending on your source.
- Homemade liquid castile soap, $16 a gallon, or cheaper if you can source less expensive ingredients. We got Coconut Oil (refined coconut oil is even cheaper) and Potassium Hydroxide from Amazon, and a gallon of olive oil from the grocery store.
2. Less plastic.
If you’re debating between 15 oz containers and gallon containers, it looks something like this.
Eight empty plastic shampoo containers weigh about twice as much as an empty one gallon container, so the little bottles use twice as much plastic. Not to mention the caps, which I’m pretty sure cannot be recycled.
If you make soap at home, a lot of the plastic usage depends on how you source the items you’re using. If you buy these things in bulk, of course you’d have no packaging (however, as noted previously, sometimes bulk is coming out of gallon sized containers).
Added Bonus: Biodegradability
It’s completely biodgradable and gentle enough to use the next time you go camping. Or shower in a waterfall. Or bathe in a lake. According to Dr. Wallace over here, it would be the same as spilling some olive oil in the stream, or better because it’s “partially digested” (whatever that means).
The coconut container has enough coconut oil to make 3 gallons of soap, the olive oil can make 5 gallons of soap and the lye is enough to make 3 1/2 gallons of soap. You can visually compare the plastic usage below – it’s not quite as much “savings” as I thought it would be though it’s still significant and even more so when compared to the smaller bottles. I would estimate that making it saves 1/2 to 2/3 of the plastic.
It is worth noting that the containers on the left are useful for other things. We use the coconut oil container to buy other foods in bulk and the olive oil container for additional soap (for now). they’re useful sizes and shapes (as opposed to the smaller bottles that I haven’t found many uses for).
If for no other reason, soap is fun to make (envision the first time you cooked something in college and it was edible) and you save a decent amount of money and lots of plastic. Castile soap is also biodegradable since it’s made out of biodegradable things. It’s dangerous for only a few minutes while the lye is reacting and the longer it reacts the less dangerous it becomes. And it’s not dangerous at all if you have your spouse do it instead. I would say the difficulty level is on par with making chili. If you can make chili, you can make soap.