Making homemade castile soap

A guide to making your own castile soap at home, which is a commonly-made gentle lye soap.

Photo Credit: Stacey Walker
By John Casteele

Using natural or homemade soap is a trend that has seen an enormous popularity in recent years; it’s a great way to know exactly what you’re putting on your body as well as keeping old traditions alive. One of the more popular forms of homemade soap is Castile soap, a gentle lye soap that’s named after a region in Spain (it’s country of origin.)

Castile soap is perhaps one of the gentlest soaps to date, a fact that makes it the choice of many mothers when choosing a first soap for their babies. It’s made with 100% pure olive oil (which is one way to tell whether or not it’s a true Castile soap), and is naturally very mild and moisturizing.

To make your own Castile soap, you’ll need the following:

2 lbs. 100% pure olive oil
2 oz. beeswax pearls
4-5 oz. lye crystals (available at most hobby and department stores)
10-12 oz. distilled water
2 oz. scented oil (herbal essential oils work best)
Food coloring (a color to match the scent of the oil is recommended)

You will also need mixing bowls (glass, if possible), wooden spoons, pots, molds, and safety glasses. Any material you use in soap making should be reserved ONLY for soap making if possible; lye can be very dangerous if ingested or gotten on the skin, and you don’t want to re-use a pot that’s had lye in it for cooking.

Once you have all of your ingredients, begin by melting your beeswax into your olive oil. Heat the oil to around 100 – 120 degrees, and set aside (maintaining the temperature of the oil). You should then put on your safety glasses and begin adding the lye SLOWLY to the distilled water; stir well. The water will begin to heat as it reacts with the lye, and will need to cool until it reaches the same temperature as the oil mixture.

Once the lye has cooled sufficiently, begin SLOWLY adding the lye to the oil. You should always add lye to other materials, and not the other way around; pouring any liquid into lye crystals or a lye mixture could cause it to splash, and lye can cause burns if it comes in contact with the skin. All lye work should also be done in a well-ventilated area.

After you’ve added all of your lye to the oil mixture, begin stirring it until it “traces”, or you can see the path of the spoon for a few moments after it passes through. This is also the time to add your fragrances and any pigment to the soap mixture (though don’t go overboard with either, since you don’t want an overpowering scent or soap that will dye your skin.) Once the soap begins to trace, pour it into the molds you have or into a greased plastic pan to allow it to set. Placing freezer paper in the bottom of the pan (if that’s what you’re using) will allow for an easier removal once the soap is finished.

Once the soap is in the molds or in a pan, cover it with a piece of freezer paper and then place cardboard or a lid on top. Wrap the soap molds in a blanket, and set in a place where it won’t be disturbed for 18 – 20 hours. After that time has gone by, remove the blankets and let it set for another 12.

You can now remove the soap from the molds (or remove it from the pan and cut it) and place it on a drying rack for about 2 weeks or longer. This allows the soap to cure, and the more time that it has to cure will make it both harder and milder in the long run. The beeswax in the soap will also make for a much smoother and silkier bar once the curing is done. The bars may not lather well, as Castile soap sometimes doesn’t, but they are one of the best soaps that you’ll find.