You can start with your oils in one of two forms — liquid or solid. Here's the lowdown on each.
Some oils — such as avocado oil and olive oil — are sold as liquids. To be used in soap, oils must be in a liquid state when mixed with the caustic solution. Liquid oils are, of course, ready to go, and they usually require little if any heating to get them ready to mix. Pouring room-temperature liquid oils into the warmed and melted solid oils is an effective way of helping to lower their temperature to the point necessary for combining the oils with the caustics. Here is a selection of the liquid oils available:
Almond oil: lubricating, occlusive, rich, and moisturizing. It has a short shelf life, so use sparingly.
Avocado oil: a thick, rich oil. High in vitamins, goes rancid slowly, and is very lubricating.
Canola Oil: comes from grapeseed oil. Almost completely unsaturated.
Can be used similarly to olive oil. Absorbs well on the skin.
Needs to be blended with some saturated oils in order to saponify well.
Castor oil: an indispensable oil for soapmakers. It has a specialized chemical makeup that provides an outstanding lather boost to lye soaps. It also helps to bind fragrance. It is a great default superfatting agent. Great in shampoos and transparent soap.
Emu oil: very beneficial in many ways. Good for superfatting. Found to be an extremely healing oil.
Grapeseed oil: is a light, slightly astringent oil. An extremely light oil that lubricates well, but leaves little residue on the skin. It is very light green and has no taste and very little odor. Slightly astringent.
Jojoba oil: actually a liquid wax that comes from the beans of the jojoba tree, native to the southwestern United States. Virtually never goes bad and is similar to the oil in human skin. It is humectant and contributes shelf life and silky feel to soap. Costly and can be used as part of a formula for a luxury soap, or as a superfatting agent in a basic recipe.
Macadamia nut oil: light, rich, and adds lubrication and silkiness to soap formulas. It has a long shelf life. Like jojoba oil, it is costly so can be reserved for superfatting or can be part of a blend of expensive oils for a luxurious soap.
Soybean oil: light and readily available. Most salad oils sold as “vegetable oil” are made from soy. It absorbs readily, does not clog pores, and is inexpensive. It is best used in combination with richer oils, as on its own it tends to have a weak, unstable lather.
Last but not least is good old olive oil. It is an excellent moisturizer and is the most overall useful soapmaking oil. True castile soap is made of 100-percent olive oil from the Castile region of Spain. In soapmaking, lower-grade, less-expensive olive pomace oil makes a hard bar and creates a quicker trace than higher grades. Higher grades of olive oil — such as virgin and extra-virgin — make a soap with a lower foam and although they make hard bars, dissolve very easily when left exposed to water. Olive oils range from light gold to deep green and can affect the color of the finished soap.
Other oils — such as coconut oil and lard — are sold as solids. Solid oils must be melted before they can be mixed with the caustic solutions. Melting points vary from just-above room temperature to quite a bit higher, so you'll need to be sure to plan carefully to avoid getting the oil solution too hot. Never let oils come to a boil and never leave heating oils unattended. A good way to melt solid oils is to place them in heated liquid oils and let them liquefy as they bring down the temperature of the overall solution. Here is a selection of the solid oils available:
Coconut oil: creates the billowy, stable lather prized in handmade soap. It should be used in combination with emollient oils to counteract coconut's potential to create a drying soap.
Lard: fat that comes from the areas around the kidneys of pigs. Makes a very hard bar on its own, but without other oils it has a low slippery lather. Best used in combination with vegetable oils that have properties it lacks.
Mango butter: yellow and grainy. An excellent superfatting agent and adds rich silkiness to soaps. It has a long shelf life.
Palm oil: one of the primary soapmaking oils. It contributes hardness and body to soap formulas. You can use it at between 20 percent and 30 percent in soap formulas.
Palm kernel oil: can be used in combination with coconut and olive to create a hard, long-lasting bar with lots of glycerin. It releases a large amount of glycerin.
Shea butter: made from the seeds of the karite tree of Western Africa. Use in quantity for a very luxurious soap. It works well as a superfatting agent.
Solid vegetable shortening: made from mostly soy oil, sometimes with cottonseed oil added, depending on brand and season. You can make a serviceable and inexpensive soap from just this oil
Tallow: used to make soap for centuries. Tallow comes from cows and game animals such as deer, moose, and elk. You can render tallow on your own or buy it from a renderer. It is more difficult to find than lard.