Cold process soap making is the traditional method of making soap by combining fat or oil (animal or plant-based) with sodium hydroxide lye, then blending in the addition of essential oils and other ingredients. The process does not involve heat, and the ingredients are not heated, which allows them to conserve their beneficial and natural properties. The cold process can be individualized to refine every amount of each ingredient, add fresh fruits and milk, and many people consider it a more creative method as the thicker consistency allows for a great number of heavier ingredients to be incorporated. The process is time-consuming and involves the handling of a toxic ingredient (lye), but this slow and traditional method is very satisfying and produces a superior product in the end. The curing process requires a warm environment and a very slow cooling process. Cold process soap is safe to use after a few days, but it is recommended to let the soap cure for 4-6 weeks in a cool, dry place with good airflow to create harder and milder bars that last longer in the shower.