Berry Rhubarb Crumble Soap Tutorial
Recipe type: Cold Process Soap
Serves: About 3-4 pounds of soap
This Berry Rhubarb Crumble Soap was inspired by the delicious summer dessert. Walnut shells and oatmeal give the crumble a realistic look!
  • Silicone Cake Pan Mold
  • 16.4 oz. Olive Oil
  • 12.2 oz. Distilled Water
  • 10.3 oz. Coconut Oil
  • 8.2 oz. Palm Oil
  • 5.7 oz. Sodium Hydroxide Lye
  • 4.1 oz. Apricot Kernel Oil
  • 2.1 oz. Castor Oil
  • 2.5 oz. Red Berry Rhubarb Fragrance Oil
  • 2.5 oz. Rolled Oats
  • Magenta Mica
  • Brick Red Oxide Pigment
  • Titanium Dioxide Pigment
  • Walnut Shells
SAFETY FIRST: Suit up for safe handling practices! That means goggles, gloves and long sleeves. Make sure kids, pets, and other distractions and tripping hazards are out of the house or don’t have access to your soaping space. Always soap in a well-ventilated area.
COLOR PREP: To ensure that the Titanium Dioxide blends smoothly into the soap batter, we recommend micronizing it before dispersing it in oil. Please note this is an optional tip but it does help with the titanium dioxide clumping in the soap. To micronize colorant, simply use a coffee grinder to blend the colorant to break up any clumps of color and prevent streaks of white from showing in the final soap. We like to use a coffee grinder that has a removable, stainless steel mixing area for easy cleaning. Then, disperse 2 teaspoons of the colorant into 2 tablespoons of sunflower or sweet almond oil (or any other liquid oil). Then, disperse ½ teaspoon Brick Red Oxide Pigment into ½ tablespoon of lightweight liquid oil. Finally, disperse 1 teaspoon Magenta Mica into 1 tablespoon lightweight liquid oil. Use a mini mixer to help get rid of any chunks.
FRAGRANCE PREP: Measure 2.5 ounces of Red Berry Rhubarb Fragrance Oil into a glass, fragrance oil safe container. Set aside.
  1. Slowly and carefully add the lye to the water and gently stir until the lye has fully dissolved and the liquid is clear. Set aside to cool.
  2. Melt and combine the apricot kernel oil, castor oil, coconut oil, olive oil and palm oil (remember to fully melt then mix your entire container of palm oil before portioning). Once the lye water and the oils have cooled to 130 degrees or below (and are ideally within 10 degrees of each other), add the lye water to the oils and stick blend until thin trace. If you’d like a harder bar of soap that releases faster from the mold, you can add sodium lactate to the cooled lye water. Use 1 teaspoon of sodium lactate per pound of oils in the recipe. For this recipe, you’d add about 3 teaspoons sodium lactate.
  3. Once you reach a thin trace, add the Red Berry Rhubarb Fragrance Oil into the soap, and use the stick blender to pulse and stir the fragrance oil into the soap.
  4. FOUR: Split off two containers with about 400 mL of soap each. Set aside. To the remaining large batch of soap, add all the dispersed Magenta Mica and ¼ teaspoon of dispersed Brick Red Oxide Pigment. Use the stick blender to fully mix in the colorants, and continue stick blending until you reach a medium trace.
  5. Pour the red soap into the Cake Pan Silicone Mold. Tap on the counter to help get rid of air bubbles. To one of the small containers of soap, add 2 tablespoons of walnut shells and 2.5 ounces of oatmeal. Use a spoon or whisk to fully mix in the walnut shells and oatmeal.
  6. Carefully spoon the oatmeal soap onto the red soap in the mold. Use a spoon to spread it evenly across the mold, and sprinkle a little extra oatmeal on top.
  7. To the final container of soap, add all the dispersed titanium dioxide and use a spoon or whisk to fully mix in the colorant. If the soap is still thin, stick blend it to a thick trace. You want the soap to hold its shape when spooned onto the soap. If the soap is not becoming thick enough with stick blending, leave the soap in the container for about 5 minutes. As the soap sits in the container, it will begin to thicken.
  8. Once the white soap has become quite thick, place eight dollops along the outside of the mold. The dollops should be placed in the center of what will become slices once cut. Depending on how large you make the dollops of white soap, you may have some soap leftover. Transfer any leftover soap into a small, individual cavity mold.
  9. Spritz the soap with 99% isopropyl alcohol to avoid soda ash. Allow the soap to stay in the mold for about 2 days to harden. Remove from the mold, and cut into eight slices. Allow the soap to cure for 4-6 weeks, and enjoy!
Recipe by Soap Queen at