The difference between cold process, hot process, and melt and pour

There are three basic soap making methods; the hot process, the cold process, and melt and pour. Learn about these methods and then choose which is best for you.

Photo Credit: Donna Lorka
By Laurel Fisher

Soap making is both practical and fun, making it a very popular hobby. People who make soap can create specialty soaps with great scents and interesting shapes. The custom bars that result are significantly less expensive to make than they are to buy in the stores, and they are perfect for personal use or thoughtful gifts. People who want to learn to make their own soap have three options: the cold process, the hot process, and melt and pour. All three of these methods have their own advantages and disadvantages, so it is important to know the differences.

Melt and pour is the easiest method. Basically, people just buy a soap making kit that will contain a pre-made chunk of soap. They then melt the soap, add various extras, and pour the mixture into molds. Although this might sound pretty boring, it is actually rather fun for people who get creative. During the melting stage, most people add some sort of essential oil; this gives the soap its nice scent. Other treats, such as oatmeal, dye, orange peel, flower petals, or thyme, can also be added. The resulting soap can be as simple or elaborate as desired, and the cost of the kit and the extra ingredients is typically still lower than the cost of store-bought designer soap.

As fun and useful as the melt and pour process is, people who use this method are not technically making soap; they are improving plain, already existing, but rather bland soap. People who actually want to make soap need to use either the hot process or the cold process.

The hot process begins by adding lye to water. This simple step is actually slightly dangerous, since people who accidentally add water to lye will inadvertently cause a minor explosion; the lye must be added to the water, not the other way around. Next, the lye mixture is added to heated fat. Some people like to do this in their crockpot. The mixture is stirred for a while before adding any desired extras, such as the aforementioned oatmeal, dye, orange peel, etcetera. The mixture is then stirred a little more to make sure that everything is evenly distributed before being poured into molds.

The cold process is very similar to the hot process, except that the mixture is not heated throughout the entire stirring process; the fat is heated, but the lye, water, and fat mixture is not heated. Some people claim that the cold process produces a soap that is softer on skin.

Both the cold and the hot process rely on lye, which is a very dangerous chemical that can burn skin on contact and is fatal if ingested. Therefore, people who use lye to make soap need to be very careful and follow detailed directions. Many people have tried to find a way to make soap without using lye, but this is impossible. Even the soap in the melt and pour soap kits was processed with lye, although people using these kits do not have to handle the lye themselves.

Children, beginners, and people who have a healthy fear of caustic chemicals are probably better off using the melt and pour method. Traditionalists might prefer the hot process, which is the oldest method that humans have used to make soap. And people who want to pamper themselves with extra conditioning soap might like the cold process.