How Is Soap Made?
Handcrafted soap can be made from scratch, by either hot or cold process, or created from a ready-made soap base. The method(s) chosen by a soapmaker are based on personal preference and the desired end result. In some cases, a final soap may contain both soap from scratch and ready-made soap base.
Made From Scratch
Handcrafted soaps made from scratch require three ingredients to become soap: oil (animal or vegetable oil, not petroleum-based oil), water and lye. These three ingredients, mixed together in correct proportions, combine and chemically change into soap - a process called "saponification". They may include other ingredients to provide additional benefits or to color or scent the soap, but these are not part of the chemical process that results in basic soap.
An accurate recipe is necessary, in order to ensure that the right amount of lye is used for the specific oils selected. A lye calculator can be used to calculate the right amount of lye, although it can also be calculated based on the type and quantity of oils being used.
The solid lye is mixed with water to dissolve it. The amount of water depends on the particular recipe, but is usually 2 to 3 times the amount of lye, based on weight. When the lye is added to the water the solution gets hot. It is important to remember that lye is highly caustic and can cause severe burns if it comes in contact with skin for more than a few seconds. Proper protective gear, including at least gloves and goggles, should be used when handling lye or incomplete soap.
Cold Process Soap
The term "cold process" refers to the fact that no heat is applied during soapmaking.
The lye solution is normally cooled to room temperature before it is added to the oils. The oils are then heated as necessary to melt any solid fats or butters and generally cooled to between 80° - 110° F, depending on the recipe formulation.
Once the lye solution and oils are at the desired temperature, they are combined together and mixed. As mixing continues, the mixture will gradually thicken. It will also get warmer, sometimes quite hot, depending on the starting temperature and the formulation. This is the chemical reaction of the oils and lye becoming soap.
Once the mixture has reached "trace" (the point at which mixture dribbled from a spoon will leave a brief trace on the surface), any other ingredients (scent, color, herbs, clays, etc) are added to the soap and thoroughly incorporated.
At that point, the soap is ready to be poured into molds. The entire batch can be poured into one mold, to be cut up after it solidifies, or the soap can be poured into individual molds, depending on the preference of the soapmaker and the formulation. Once in the mold, the soap is left to cool and finish the saponification process. Often it is insulated in the mold to slow the cooling process and increase the saponification time.
Once the soap is completely cool and solid, it can be unmolded. If it was poured into one mold, this is the time to cut it into bars. The soap will be solid, but should be soft enough to cut.
The final stage is curing the soap for 3 - 8 weeks to allow the excess water to evaporate out. The length of time will depend on the amount of water used in the soap as well as the temperature, relative humidity and air circulation where they are located. The soap can be used before then, but it will still be relatively soft. The longer the water is allowed to evaporate out of the soap, the harder the soap will be.
Hot Process Soap
"Hot process" soap refers to the fact that an outside source of heat is applied to make the soap.
With hot process soap, the lye solution and oils are mixed together and then an outside source of heat is used to keep the temperature up. The added heat reduces the time needed to ensure the chemical process (saponification) is completed.
Once the soap is completed, it is still in liquid form because of the higher temperatures (essentially, it is soap in a "melted" form). When fully saponified, it can be poured into molds in the same manner as cold process soap, and cut as needed when cooled and hardened.
Because hot process soap is fully saponified when poured into the molds, no additional time is needed in the molds to complete the process. Hot process soap may still be cured to allow additional water evaporation to harden the bars, although less curing time, if any, is generally needed.
Once the bars, whether made by cold or hot process are sufficiently cured and hardened, they can be packaged as desired and, of course, used!
Ready-Made Soap Base
Ready-Made soap base is already soap, so all the steps necessary to producing the soap itself are eliminated. The soapmaker's concentration can be focused on the artistic, aesthetic and beneficial aspects of the soap.
Also referred to as "melt and pour" or "MP" soap, ready-made soap base comes in a solid block. Following the manufacturer's directions, the soap is heated up in order to melt it into a liquid state. At that point, colors, scents and other ingredients can be added to the soap. Once the additives are incorporated into the soap, it is poured into molds and allowed to cool and solidify. Once hardened, it can be unmolded and is ready for packaging and/or use.
Ready-Made Soap base is available as both clear or opaque soap and is especially useful for specialty shaped soaps for which a wide variety of individual molds are available. With the versatility of ready-made soap base, soapmakers have a wide range of creative possibilities, including placing colorful embeds of soap or even toys in soap or producing soaps that look like food or other items.