I had plans to make candles out of last weekend’s rendered tallow, and after I had the candles mastered, I planned to graduate onto soap, which is more chemically complicated. But once I started reading soap recipes, learning about the chemistry, reading tutorials, candles sounded boring. Soap it is!

Do you know what your soap is made of? Unless you buy handcrafted soap at your farmer’s market, or a natural brand that emphasizes the absence of animal products, there’s a good chance your soap contains beef fat, which is called sodium tallowate on the label. That includes all the biggies: Dove, Jergens, Zest, Ivory… don’t be alarmed! Beef fat makes great soap, and specifically hard soap, so your bar lasts a good long time. Other fats contribute different properties. Coconut oil, for example, creates a nice lather. Olive oil makes a soap creamy and conditioning. There are a bajillion types of oil to create a soap to suit every purpose.

The recipe for soap is simple: fat+sodium hydroxide (lye) = soap. Everything else is just decoration. I wanted to keep my soap natural, so I decided to use turmeric, paprika, and Brazilian red clay as colorants, and lemongrass essential oil for scent.

There are some very good soap-making tutorials out there, specifically the excellent Humblebee & Me blog, which includes photos of the entire process. Since this was my first time making soap, I’d caution you against using this post as a tutorial. There is much greater wisdom out there on the interwebs!

This Soap Calculator is an essential tool for the soap maker. It calculates the amount of lye, water, and fragrance you’ll need in both ounces and grams. I knew I had at least 4 lbs of beef tallow to work with, but after doing some research, I learned that I should probably mix the tallow with some other oils to improve the properties of the soap. I was aiming for a 5 lb loaf of soap, so that meant reducing my tallow quantity. In the end, I calculated the following:

  • 36 oz tallow
  • 16 oz coconut oil
  • 16 oz olive oil
  • 25.8 oz water
  • 9.7 oz sodium hydroxide
  • 2.5 oz essential oil

Note these ounces are by weight, not fluid ounces.

First, bring the oil to liquid state at the lowest temperature possible. You’ll eventually have to get it back down to around 110ºF, so any temp above that is heat you’ll just have to lose later.

Melting tallow

Melting tallow

I brought my coconut oil to liquid state in a warm water bath and mixed with the olive oil, then dumped in the frozen tallow. By the time it was all completely melted, my oil was up to 175º, so I brought it outside to cool.

The next step is mixing in the lye, which is supposed to be almost exactly the same temperature as the oil when it’s added. Timing the temperature turned out to be the most complicated part of the whole process. After you mix your carefully measured lye with your carefully measured water, the solution immediately heats up. I expected this to happen, but I didn’t know how much it would heat up. I made the mistake of cooling my oil down to 120º before mixing the lye and water in a plastic pitcher, and the lye heated itself up to 189º! Then it was the lye’s turn to sit outside and cool. By the time it finally cooled to 120º, my oil was too cool and needed to be heated back up on the stove. But then I overheated it. Back out to the porch to cool. You get the picture. The end goal is that the oil and lye solution should both be between 110-115ºF when you mix them.

Once temperature nirvana was at last achieved, I added the lye to the oil. In the old days, you had to stir by hand for an hour or more to fully combine the substances, but we’re lucky that immersion blenders significantly speed the process. The goal is to achieve “trace,” which is a thickness of similar viscosity to stirred yogurt. It took about 10 minutes with my immersion blender.

Once a thin trace is achieved, it’s time to add any scents or colorants. My loose plan for this soap was to be half yellow and half red, with a thin straight line of vibrant red-orange paprika between the two layers. After adding the lemongrass essential oil, I dumped what I guessed to be half of the soap into a second bowl, added the turmeric to the first and the red clay to the second, and continued blending with the immersion blender to bring the yellow layer to a firm trace. This took longer than expected. Once I could finally drizzle the soap on itself and see the “trace” of the lines left behind, it was ready to pour into the mold, which Joshua sweetly built for me earlier that morning. I lined it with freezer paper. After pouring into the mold, I dusted paprika over the yellow layer using a tea strainer.

But by the time I got to the red clay portion, it had cooled a bit and came to firm trace FAST, much faster and thicker than the yellow layer. The yellow bottom layer would need to be thick enough to suspend the red bottom layer without breaking through the surface tension. I held my breath and gently poured. The red layer sunk and swirled, and the paprika gushed up toward the top. Sigh. It was ambitious for a first soap, perhaps. In hindsight, I should have given up on the neat color blocks at this point and just deliberately swirled the colors, but I left it as poured just to see what would happen.



The next step is to insulate your soap to allow the second chemical process to happen: saponification. After molding, the soap heats itself back up again and gels, and something in this process is what officially transforms the caustic lye into benign body soap. I don’t really get it.

24 hours later you can cut your soap. After cutting, I realized that my gestalt 50/50 red and yellow was WAY OFF. Next time I’ll measure. I would also use more turmeric for a deeper yellow. My dad says these look like slabs of raw bacon, which is maybe appropriate, given the origins of this project. Maybe next time I’ll make bacon scented soap. The dogs think this is an excellent idea.

Word of caution, repeated from Humblebee & Me: lye should be treated with a healthy dose of respect. Many soap making tutorials recommend wearing gloves and goggles when working with lye. I had no intention of touching the stuff, and I mixed it outside so the noxious vapors wouldn’t stink up the house, so I ignored both of these suggestions. But I still had to stir the hot lye to help it cool, and the steam it gave off as it cooled was enough to mildly burn my hand, which was itchy and raw for the next 24 hours. Next time I’ll wear gloves.


5 thoughts on “Saponification!

  1. Regardless of whether they look like raw bacon I always enjoy your posts. have you tried the soap yet? I’m not sure it has gone through the final cure yet. How long does it need to set before use?

  2. This is your uncle, the chemical engineer talking: Sodium hydroxide should be treated with more respect than any acid you ever work with. If you ever get a lye solution on your skin, you will notice how slick it feels, almost like soap. Well, that is exactly what is happening, the lye is saponifying the fat in your skin, turning it into soap. Don’t be scared to work with chemicals, but always treat them with respect.

  3. Pingback: Body Lotion Bar DIY: Beef Tallow Part Deux | baD.I.N.K.adink

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