Pure & Mild Castile Soap

About: Adventures in sustainable living from a fourth-floor walk-up. Recipes, homesteading, and gardening — all from an urban point-of-view.

Of all the products I’ve made myself, soap was always the DIY project that dare not speak its name. The ingredients were simple, the outcome was delightful, but there was that middle part with the horrible threat of flesh-eating burns and death that kept me relegated to scrubs and salad dressings.

But when I came across a recipe for a pure olive oil soap, it was so simple, I couldn’t resist. It seemed the perfect place to start.


50 oz. olive oil
6.3 oz. lye
15 oz. distilled water

This should yield about 30 two- to three-ounce bars. (Holy crap, right?) I’ve halved the original recipe to make it more manageable after I found myself working with over ten pounds of ingredients once I got going. This one is more… apartment-sized.

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Step 1: Pure & Mild Castile Soap

To get a sense for the soap-making process before you do anything — the steps, the tools, and how to be safe — I recommend The Crafty Gemini’s YouTube tutorial.

I started by heating the olive oil on the stove. I knew it would hold its heat while I made the dreaded lye water. Like most things in life, the lye water actually wasn’t that hard. Aside from the fumes smelling like instant death, the only unexpected moment of panic was measuring the lye, when a static charge on my measuring cups sent lye granules flying everywhere but in.  After I made the lye water outside, I poured it into a 5-gallon bucket with my olive oil and blended it for all it was worth until it was about the consistency of school cafeteria custard. (It looked about as appetizing, too.) This is another reason I halved the recipe, because 10 pounds of flesh-eating sludge can be surprisingly daunting in the moment.

Step 2: Pure & Mild Castile Soap

Back inside, I’d lined shallow cardboard boxes and cut-out milk cartons to act as moulds. I slopped in my soap, and decided to add essential oils to a few now that I had smaller batches. The rule for essential oils is about a half-ounce per pound of soap. So I grabbed one mould, weighed it, measured some essential oils — I went for the peppermint and rosemary — and just poured it on top and mixed it all in. Then I put the soap moulds off to the side and covered them with a garbage bag, then blankets to insulate them overnight. (Oh, all right, it was dirty laundry.)

I didn’t understand that last step until the next day when I took the blocks of soap out for cutting. The soap that’d been insulated was rock hard, while the dirty mixing bucket I’d left outside in the cold had soap, too, but kind of smooshy to the touch. Heat is clearly a commodity. I cut 1-inch-thick bars that (depending on the moulds) came out to about 2 or 3 ounces apiece. (And, yes, I was squealing with delight with every bar.) Then I arranged them to dry and left them alone for about 6 weeks to cure into nice, hard bars.

Step 3: Pure & Mild Castile Soap

Why homemade soaps?

I don’t know about other cities, but in New York, a bar of natural soap like Dr. Bronner’s is almost $5. But if I divide the number of bars I made in this recipe from the cost of all my ingredients — not counting the scale and thermometer and all the upfront stuff — a bar of quality, natural soap only costs me 80¢ a pop. Eighty cents! Not too shabby, huh?

A lot of people are probably thinking, “But, Crunchy Urbanite, doesn’t bar soap dry your skin?” Nope. Conventional bar soaps do dry your skin, but that’s because conventional bar soaps aren’t soap anymore. They’re detergents. Castile soaps like this one create glycerin in the saponifying process, which your skin loves, and which chemical companies remove from conventional bar soap to sell back to you in more high-end products like moisturizers and lotions.

“But, Crunchy Urbanite,” you’re saying. “You’re so gung-ho about organics; how come you didn’t say to use organic olive oil?” (Or at least, that’s what I said to myself.) The truth is, when I saw how much it would cost me to buy large quantities of organic olive oil, I did a little sleuthing. Olive oil is one of those crops with next to no toxicity difference between conventional and organic. Personally, I’ll still buy organic for cooking, but for something like soap, I went conventional.

Smelling my soaps curing for six weeks was incredible. But using them was even better. Pure olive oil soap doesn’t lather much — a frothy lather typically comes from added detergents for show, anyway — but, wow! What a great clean.

I think I’m hooked.

Original post from The Crunchy Urbanite

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    16 Discussions


    Question 5 weeks ago on Step 1

    Hi, You were saying that one could use coconut oil. How do you substitute or use half and half.


    2 months ago

    Crunchy urbanite, what kind of lye did you wear?
    I was wondering which "brand" and "type" of lye I should use. Just so that I understand what product it is. That way I can search more easily.


    6 months ago

    Castile soap is best if allowed to cure for at least 6 months. Less than that and your soap won't last long and the slime that it produces instead of suds is worse. Best yet, let cure for a year.
    Something else, all ingredients should be weighed, except for the water because, an ounce of water weighs an ounce.
    Almost as important is to NEVER, EVER, set any kind of soap to cure on metal!!! The soap will affect the metal, even if it's plastic coated, and that will cause what soapers call DOS: dreaded orange spots. Those are areas of rancid soap and it's disastrous. It changes the color and smell of the soap.
    As for the smell of soap curing, it's only pleasant if you've scented the bars. Otherwise, those first few days the fumes are eye-watering. I know this because I made my first batch in an efficiency apt that has little to no ventilation. Nowadays I'm living and making soap in a bigger house with a porch. If you don't have one of these, turn on your stove's extractor and make your soap there. Then leave the soaps to cure where there's good ventilation.
    Finally, learn to use a lye calculator and run EVERY soap recipe through it. Google for one but I usually use SoapCalc.net. And I joined the soapmakingforum.com for LOTS of tips and guidance on making the best soap for you.
    I wish everyone a great soaping journey!!
    P. S.: if you REALLY want to learn to make great soap, and experiment with it, try watching the channel Soaping101's on YouTube. Katherine is a great teacher, her voice is NOT annoying, and she gives you the best info, technical and scientific, without giving you a headache. Plus her recipes are infinitely modifiable.
    I'm including one of my recipes, run through SoapCalc.net, that I've used more often than not when trying new additives, but also add just a basic soap.


    3 years ago

    Great Instructable!!
    - btw, Castile soap is gentle on skin because it doesn't have a shitload of nasty additives that're in the usual factory-made soaps, not because of glycerine which creates the illusion of soft, smooth skin, as its a humectant. This means it absorbs moisture and the closest supply of moisture is (unfortunately) our skin leaving it soft, smooth and dry. Soap being left on our skin will have a drying effect and why we wash it off. And also why we feel the need to keep using moisturisers when we aim to help our dry skin - because 99% of them all contain glycerine. For those who don't feel their skin has become dry when using glycerine-based skin care, welcome to the world of premature aging!
    Thought would mention (for those that are interested) other sources of lye:
    - wood ash (yes, the ash that remains after wood fire has burned down), when added to water forms lye;
    - caustic soda.


    Reply 3 years ago

    I make my soaps with both olive and coconut oil. I'm not sure that you would want to use JUST coconut, or JUST sunflower by themselves. . . I think I remember reading in one of my books that you'd have to use an insanely large amount of them to achieve the same results, which is why I never bothered.


    4 years ago on Introduction

    Fantastic! Really looking forward to trying this. Thanks for a great 'ible!


    5 years ago

    Could this be turned into shower gel? Or liquid soap?


    5 years ago on Step 2

    Thanks for posting! I've been itching to try my hand at homemade soap for a while now and hope I can try this soon.

    I am curious, where did you end up getting the lye, did you order it online?

    1 reply

    Reply 5 years ago on Introduction

    You can get lye as a drain cleaner from your local hardware store (Ace, Home Depot, etc.) Just make sure it's the only ingredient, it comes in a powder/crystal form.

    Marcaine Art

    6 years ago on Introduction

    I love this. Have you tried to make any with herbs or other things mixed in like oatmeal for scent and scrubbing effect?

    1 reply

    Thanks, no, not yet. I have a recipe for coffee-grounds soap that I'm curious to try next. Lord knows there're always enough ground at my place... ;)