How soap is 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.
Try the HSCG Lye Calculator
To dissolve the lye, it is mixed with water. Depending on the particular recipe, it usually takes two to three times more water than lye to do this. When lye is added to water, the solution gets hot. Lye is highly caustic and can cause severe burns if it comes in contact with skin for more than a few seconds. Soapmakers use proper protective gear, including at gloves and goggles, when handling lye or incomplete soap.
The oil used is either animal or vegetable -- not petroleum-based. When mixed in correct proportions, these three ingredients combine and chemically change into soap. This process is called "saponification". While other ingredients may be added (oils, herbs, etc.) for additional benefits or to color or scent the soap, these are not part of the chemical process of saponification.
To ensure that the right amount of lye is used for the specific oils selected, a recipe is key. A lye calculator can be used to calculate the right amount of lye, although it can also be determined based on type and quantity of oils being used.
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. Mixing causes the solution to thicken and heat up. Depending on the starting temperature and the formulation, it can get quite hot. This is the chemical reaction of the oils and lye becoming soap – saponification.
Once the mixture has reached "trace," defined as the point when 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.
The soap is now ready to be poured into molds. The entire batch can either be poured into one mold, to be cut up after it solidifies, or individual molds can be used. 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 cool and solid, soap is unmolded. If using one “loaf” mold, it is now but into bars. The soap will be solid, but still soft enough to easily cut.
The final stage is curing. The soap sits for three to eight weeks, allowing excess water to evaporate. The length of time depends on the amount of water used in the soap as well as temperature, relative humidity and air circulation. While soap can be used before then, but it will still be relatively soft. The longer water is allowed to evaporate out of the soap, the harder the soap will be.
Once cured, the soap can be packaged – and more importantly – used!
Hot Process Soap
"Hot process" soap gets its name because an outside source of heat is added. With hot process soap, the lye solution and oils are mixed, then additional heat is used to maintain a high temperature The added heat reduces the time needed to complete the chemical process (saponification).
Once finished, soap is still a liquid because of the higher temperatures (melted form). When fully saponified, it can be poured into molds in the same manner as cold process soap then cut 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.
Just like cold process, once cured and hardened, the soap can be packaged – and more importantly – used!
Ready-Made Soap Base
Ready-Made soap base is already soap, so the saponification process is eliminated. This allows the soap maker to focus on 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 to melt into a liquid state. This is when colors, scents and other ingredients can be added to the soap. It is then 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 in both clear and opaque form. It is especially useful for specialty shaped soaps. The versatility of ready-made soap base gives soapmakers more creative freedom. This includes soap that looks like food or other objects, as well as embedding colorful pieces of soap or even small toys in the bar.
Handcrafted soapmakers take great pride in developing unique recipes to create signature products. Typically food-quality, natural ingredients are used starting with vegetable oils such as olive, coconut, or palm, or purified tallow or lard. To these, the soapmaker may add specialized oils, nut butters or seed extracts to bring the desired qualities to the finished bar.
Fragrance oils or plant-based essential oils are typically added for scent.
To affect color or texture, soapmakers rely on cosmetic-grade pigments or dyes, botanicals, herbs, spices or other natural ingredients. Most soapmakers also make "simple soap" with no additives or scent for those with allergies and skin sensitivities.