Mint soap leaves you feeling refreshed and invigorated throughout the day after bathing with it. While you can buy mint soap at the store, commercially produced mint soap may contain an artificial mint fragrance instead of pure peppermint or spearmint oil. Organic mint soaps usually contain natural essential oils, but can still cost a lot more than you want to spend. Get the best of both worlds by making your own fragrant homemade mint soap using essential oils and other natural ingredients.
Remove the top from the bottom of a double boiler. Pour water into the bottom half of the double boiler, and bring it to a boil on the stove. Place 2 pounds of cubed melt-and-pour soap base into the top of a double boiler and fill the bottom of the double boiler half-full of water. If you have a solid block of melt-and-pour soap base, cut it into cubes with a sharp knife before placing the base into the double boiler. Set the top of the double boiler back on to the bottom after the water inside it begins to boil.
Heat the double boiler on an stove over medium to high heat until the melt-and-pour soap base melts, stirring occasionally with a wooden spoon. Place a high-heat glass candy thermometer into the soap base. Once it reaches 110 degrees Fahrenheit and appears smooth and even, add 20 drops of either spearmint or peppermint essential oil or 10 drops each if you prefer a mixture of the two fragrances. Stir the oils into the soap base thoroughly with a wooden spoon.
Add three to five drops of green food coloring into the mixture, stirring with the wooden spoon until the color appears evenly distributed throughout the mixture. Add more drops if you prefer a bright green mint soap.
Spray the soap mold with an oil-based cooking spray. This lightly greases the mold to make it easier to remove the soap once it hardens. Pour the soap mixture into the prepared mold and allow the mixture to cool completely. As it cools, the soap hardens. Pop out the soap -- if using individual soap molds -- or remove and cut the soap into bars, if you used a block mold.