In part one of this post, I presented a formula for a very nice soap, provided links to the ingredients, and explained just how making this soap at home could save you money. But I didn’t explain how to make the soap.
I’ve put that off long enough; it’s time to get our hands <ehem> clean.
In baking, it is not uncommon for a recipe to be broken up into assembling the dry ingredients and the wet ingredients in separate steps, bringing them together, and pouring the result into a pan or molds. Soapmaking involves a similar approach1:
- Make the lye.
- Blend the oils.
- Add the lye to the oils.
- Pour into a mold.
- Cure.
Making the Lye
In a well-ventilated room, wearing long sleeves, rubber dishwashing gloves, and safety goggles (even just eyeglasses are better than nothing), place a suitably sized Pyrex measuring pitcher on an electronic food scale2, tare the scale to zero, and set the units to grams. Pour the appropriate amount of distilled water (preferably refrigerated) into the pitcher. Tare the scale to zero again. Next, slowly and carefully pour in the appropriate amount of sodium hydroxide into the pitcher. Gently stir with a wooden spoon until the sodium hydroxide is completely dissolved. Set it aside in a safe place to let it completely cool. Rinse the spoon. You now have a 500 ppt solution of Lye (this just means equal parts NaOH and H2O).
You’ll notice that this is an exothermic reaction; the solution gets very hot quickly. Be very careful working with lye as even when it has completely cooled it will burn the skin. Don’t let any get on your skin or in your eyes.
Blend the Oils
The formula I provided has three oils, one that is liquid at room temperature, two that aren’t. We want a nice liquid blend of all three. Place a large stainless steel (never aluminum) stock pot on the scale and tare it. Scoop out the appropriate weight of the solid oils into the stock pot, taring the scale after each one has reached the desired weight. Finally, pour in the liquid (olive) oil until the appropriate weight is reached.
Be exact in all your measurements. Be slow and deliberate and remember to tare the scale before weighing a new ingredient. If you end up with too much of something (accidentally of course), it better be oil or water.
Add the Lye to the Oils
When the lye has cooled to room temperature, and you’re ready to make soap, get your soap mold ready and place the stock pot of oils over low heat on your stovetop. When the oil solids have all become liquid give it a stir with the wooden spoon and monitor the temperature with a meat thermometer until they’ve reached 43°C or 109°F. Remove from the heat and put on your gloves and safety goggles.
Next, pour the lye into the oils and gently stir. Stir until the raw soap mixture reaches ‘trace’. Trace is the point when the surface of the mixture no longer heals itself. In other words, if you drag the spoon across the surface, and the line it creates disappears immediately you have not yet reached trace. But the very first time you drag the spoon across, and the imprint of the line is still faintly visible thereafter, you’re at trace3. Reaching trace can take a few minutes so be patient.
Pour into the Mold
Immediately after trace is reached, pour the raw soap into the soap mold. Do this carefully as raw soap can still burn the skin.
If trace snuck up on you to quickly, you might have something quite a bit thicker than milkshake consistency. Here you can scrape out the soap into the mold and hopefully it settles. Rare is the soap maker who hasn’t waited too long to call trace. The result? Soap in stock pot that has to be cut out and salvaged or worse, washed down the drain. It is better to call ‘trace’ early than to be absolutely convinced you’re at trace. How about that for a vague instruction?!
If your mold has a lid, go ahead and put it on there. If not no worries. Either way, place the mold on a rack in the middle of the oven with no heat for a few hours. This is just an insulated environment that slows the cooling of the mold and allows the saponification to complete.
After about four hours you can have your oven back, but don’t remove the soap from the mold for a couple of days. The soap in the stock pot will be easier to remove after a couple of days, so put off the cleaning of the pot for a couple of days too.
Cure
I resisted a reference to the band. You’re welcome.
After two days, the soap should be pretty hard. If so, remove the soap from the mold and cut through the slab on a cutting board to get 8 to 12 bars depending on how big you want them. Then stand them up on a shelf or lay them on a rack so that they get as much air as possible.
The soap is now safe to use, but they would go very quickly. However, if we leave them to cure for at least two weeks, preferably four weeks, they will be considerably harder and will last much longer when they’re put to use.
1The process outlined in this post is referred to as the ‘cold process’. Does it involve heat? Yes. But apparently, there is a ‘hot process’ that is used commercially, and that process involves boiling fats and oils in an excess of lye. Eventually, fully saponified soap rises to the top of the vessel and the glycerin is lost with the extra lye at the bottom. The version I lay out here is a modified version of that taught by Kevin M. Dunn in his book ‘Scientific Soapmaking‘. Written for the layperson, it is an excellent book that bridges the gap between poorly written, recipe-heavy cottage industry articles and scientifically dense, textbooks for chemists in the commercial soap industry. I highly recommend purchasing this book if soapmaking becomes a habit.
2In part one, did I assume that everyone has a 7kg capacity (minimum) electronic food scale with a readability of 1-gram increments? No. Did I completely forget and leave out the scale when preparing my financial tables in part one? Yes. Will, I go back to edit that post? No.
3If you’re adding essential oils for fragrance, this is the time to do it. The weight of the essential oils should be about 3% of the weight of the primary oils. Once added, quickly stir for a couple of seconds to distribute and then pour the mixture into the mold.