Keep your eyes and skin safe by wearing goggles and work gloves.
Using a scale, weigh all your ingredients exactly as told in the recipe.
Slowly heat your oils over the stove in a stainless steel pot.
Add water to a heat-resistant 4-cup measuring cup. Very slowly add your lye while stirring constantly. It is best to do this in a well ventilated area as there will be very strong fumes you will not want to breathe in.
Place your lye mixture in an ice bath. It will need to cool to 115°F. Your oils should also measure at 115°F.Reheat them if necessary.
Using an immersion blender, pour the lye mixture into the oils.
Continue blending until your mixture reaches a light trace or the consistency of pudding.
To make the marbled effect, remove a couple tablespoons of your soap and mix it with the charcoal. Once thoroughly mixed, add the batter back into the bowl. Use a spatula to pull it through the mixture three times in different directions.
Pour your mixture into a soap mold. If you don’t have a soap mold, a cleaned and dried 1L milk carton will also work.
Cover your mold with towels and cardboard, then set it somewhere warm (such as the top of the fridge) for 48 hours.
After 48 hours, remove your soap from the mold. Cut into equal sections.
Place your soap on a wire rack and allow it to cure in a cool and dark place for 6 weeks.