< Previous Next >
How To Make Easy Cold-Processed Lavender Soap
By Meagan - July 24, 2015

How To Make Easy Cold-Processed Lavender Soap

Guest post by Jan of The Nerdy Farm Wife Soap is what's made when pure oils meet a caustic substance. In times past, our grandmothers used potash made from wood ashes for this job. Because there was no way to determine the strength of those ashes, soaps often turned out lye-heavy and harsh. Today, we have a standardized product called sodium hydroxide (lye). It takes the guesswork out of making soap and ensures a balanced bar every time. Every molecule of lye will react with molecules of oil, in a chemical transformation that changes both of them. No lye remains in the final bars of soap. Sometimes you can buy lye locally at small hardware or feed stores, or you can also order it from Amazon.com. Today I'm going to be sharing an easy cold-processed lavender soap recipe with you. This sweetly scented lavender castile soap is made from 100% olive oil. It starts off a little soft, then over time cures into a hard, but gentle bar that's perfect for those with sensitive skin. While it's a wonderful cleanser, it has a low amount of lather. Because of this, some like to boost the bubbles by adding a little bit of second oil to the mix. If you'd like to do this too, just check the "Variations" section below for instructions on how to do so.

Easy Cold-Processed Lavender Soap

  • 1 cup dried lavender buds
  • 30 oz (850 g) olive oil
  • 8 oz (227 g) water
  • 3.85 oz (109 g) sodium hydroxide (lye)
  • 1 to 2 tbsp (15 to 30 ml) lavender essential oil
  • Soap making pot or deep mixing bowl (stainless steel, heavy duty plastic, or enamel lined)
  • Heavy duty rubber or silicone spatula or spoon
  • Small cup or container for weighing dry lye
  • Stainless steel or heavy duty plastic pitcher for weighing water and combining lye solution
  • Thermometer (one designed for candy making works well)
  • Digital scale
  • Stick (immersion) blender
  • 3 pound soap mold or similar equivalent such as a 9” x 5” glass loaf pan
  • Rubber or latex gloves and a pair of goggles
Directions: Step 1: Make the Lavender Infused Oil Place the lavender flowers in a quart jar then pour the olive oil over them. If you're not in a hurry, you can close the jar tightly and then tuck it away for around 4 weeks before straining. For a quicker infusion, keep the jar uncapped and set it down into a saucepan containing a few inches of water, forming a makeshift double boiler. Set the pan over a low burner and gently heat the oil for 1 to 2 hours. Strain the oil from the spent flowers and weigh it. Add extra olive oil as needed until it weighs 30 ounces. Step 2: Preparation Gather all of the ingredients and equipment needed for this recipe. I like to work in my kitchen sink, so that any spills are contained. For easier cleanup, line the nearby counter with wax paper to catch drips and dribbles as they happen. Put your gloves and goggles on to protect your skin and eyes from any stray splashes and consider wearing long sleeves as well. If your soap mold isn't silicone, line it with parchment paper or an inexpensive unscented trash bag to keep the soap from sticking. Step 3: Make the Lye Solution Weigh 8 ounces of water into a heat proof plastic or stainless steel pitcher or container. Using a small jar or cup that's reserved for lye use only, weigh out the 3.85 ounces of lye. Carefully pour the lye into the water. Stir with a heavy duty rubber or silicone spatula until it's completely dissolved. The mixture will get very hot. It will also give off strong fumes for a few moments; so turn your head away and avoid breathing those in. Set the lye solution in a safe place away from pets and children and allow it to cool until it's around 90 to 110 degrees Fahrenheit. Step 4: Make the Soap While the lye solution cools, weigh out and pour your oil into the soap making pot or deep mixing bowl. This should be stainless steel, enamel lined or heavy duty plastic. Avoid using aluminum or non-stick surfaces like Teflon since they can react in a bad way to lye. Heat the oil gently until it's around 90 to 110 degrees as well. Once the lye solution and oils are in somewhat of a similar temperature range, it's time to make your soap! Pour the lye solution into the oil and hand stir for about 30 seconds. Using your stick (immersion) blender, stir in short spurts of 20 to 30 seconds blending with the motor on, then 20 to 30 seconds hand stirring with the motor off. This keeps from putting too much air in your soap and lessens the chance of burning out your stick blender. Keep stirring until you reach trace. Trace is when your soap batter is thick enough to leave a faint impression, or “trace”, when you drizzle it across the top surface of itself. It's very similar to a thin pudding. Pure olive oil soaps usually take a long while to reach trace. Since this recipe has a reduced amount of water to compensate for that tendency though, it should only take between 5 to 15 minutes. Step 5: Adding Extras and Pouring Once trace is reached, stir in the lavender essential oil and pour the soap into the prepared mold. If you'd like, you can sprinkle a light layer of lavender buds over the top of the soap for decoration. Resist the urge to stir them into the soap batter however, since they'll eventually turn an unattractive shade of brown. Cover the mold with a layer of wax paper and then the mold's top. If it doesn't have a top, a piece of cardboard works too. Tuck a quilt or heavy blanket around the mold and let it sit undisturbed for at least 24 to 48 hours. Castile soap starts off softer than other types, so it may need to stay in the mold for up to a full week. That's okay and perfectly normal. Step 6: Finishing Up Once your soap has hardened in the mold, you can remove it and slice it into bars. All cold process soaps should be cured in the open air on sheets of wax paper or coated wire racks for at least 4 weeks before use, but castile soap benefits from an even longer time. Some people let their bars of castile cure for 1 year before using! You don't have to wait that long, but over the next few months, you should notice that your soap gets harder and nicer to use as the water evaporates out. Variations: If you'd like to make an “Almost Castile” soap that lathers a little bit better, you can try adding a second oil to the mix. Sometimes, this requires a change in the lye amount, depending on which type of oil you use. One option is to change the recipe to 27 ounces olive oil, 3 ounces castor oil and the same amount of lye, water and lavender essential oil. When castor oil is added to soap, it contributes nice bubbles and stabilizes the lather of other oils. Another idea for boosting bubbles is to add coconut oil. Coconut oil also adds hardness to a bar of soap. Try 27 ounces olive oil and 3 ounce of coconut oil. Because it takes a different amount of lye to turn coconut oil into soap, you'll need to adjust your lye amount to an even 4.0 ounces. The amount of water and lavender essential oil will be the same.
So what do you think? Do you think you could make this recipe at home? Have you ever made your own cold-processed soap before? If so, how'd it turn out?
Jan Berry is a goat chasing, soap making, homeschooling farm wife who loves turning weeds into beautiful things. You can find more of her soap projects and herbal recipes at TheNerdyFarmWife.com.


  1. April king
    How can you incorporate goat milk into this recipe?
    1. Jan @ The Nerdy Farm Wife
      Hi April!

      Instead of water, use frozen or slushy goat's milk instead. You'll want to add your lye slowly and mix well, so that the milk won't scorch.

      You can keep the soap at room temperature (for an off-white soap) or if you want to try to get a very white bar, you can pour it into the mold, then refrigerate or freeze it overnight (or for around 12 hours), before returning to room temperature. Let the soap stay in the mold an extra day or so, if you refrigerate or freeze it, because it will be very soft at first.
  2. spghirotti
    What does the lavendar infusion add to the soap? Does it add more lavendar smell?
    1. Meagan
      I'm not a soap-maker, but my guess is that it adds the benefits of lavender into the soap. I don't know if it would add that much smell... maybe a little. Sorry I couldn't be more helpful.