Common soap making oils – in brief
All oils and butters that are composed of triglycerides and form soap in reaction with lye are called base oils or fixed oils. Any natural base oil or fat can be used to make soap, but not all of them can yield a good soap. The best soaps are made by combination of several different oils and butters. There are only few oils, like olive oil, which can yield a good soap when used alone.
Some oils like coconut, olive or palm oil are especially important and widely used for obtaining desired soap qualities (cleansing, hardness, lather/bubbles, skin conditioning). These oils can be considered as basic soap-making oils. Numerous other oils are used to partially or entirely replace some of the basic oils or to provide additional qualities, e.g. moisturizing, conditioning etc.
Soap properties described here for individual oils refer to soap made of 100% of one particular oil. When used as one of the oils in a recipe, each oil certainly contributes to overall soap qualities in a specific way.
Usage rate means proportion of a particular oil in total oil content used in a recipe. Recommended usage rate is flexible and it depends on properties which a particular oil adds to soap and other oils in the recipe. Depending on the specific combination of oils, usage rate can be adjusted to achieve desired soap properties.
Here is a brief description of some of the most frequently used oils in soap making:
Coconut oil
Coconut oil belongs to hard oils because it contains mainly saturated fatty acids and it is solid up to 24oC (76oF). It makes a very hard, white bar of soap with lots of bubbles and excellent cleansing abilities. Recommended usage rate is 15-30%. If used more than 30%, it may have a drying effect on the skin and should be followed in high superfat. Coconut oil saponifies easily.
Olive oil
Olive oil is soft and liquid at room temperature. It is different from all soap making oils because it initially yields soft soap which becomes very hard after a few months' aging time. It makes soap with excellent conditioning properties, but with very low bubbles. It can be used in any rate up to 100%. It saponifies slowly, so a little more mixing is required. As olive oil slows down trace, it is an oil of choice for complicated swirling.
Palm oil
Palm oil is solid at room temperature. It makes hard soap with creamy, stable lather and it often plays the role of a “soap filler”. Recommended usage rate is up to 50% of total oil content in soap. Palm oil is often used as a substitute of tallow in making the vegan version of classic soap recipes.
Palm kernel oil
Palm kernel oil is very similar to coconut oil in fatty acid profile. It is solid up to 24oC (76oF). Palm kernel oil makes a hard, almost brittle white bar of soap with lots of bubbles and great cleansing abilities. Recommended usage rate is 10-30%. If palm kernel oil is used too much in soap, it will leave your skin dry.
Castor oil
Castor oil is soft and liquid at room temperature. It makes a soft bar if used in high proportion. Castor oil is an excellent humectant and bubble buster. Even in a small rate, it contributes to fluffy and stable lather, which makes it suitable to be used as a foaming agent in soap. Recommended usage rate is 3-8%. It can accelerate trace if used more than 5%.
Sweet Almond oil
Sweet almond oil is a soft oil known by its moisturizing properties. Almond oil is frequently used in soap making because it supports lather and increases moisturizing and conditioning properties of soap. It makes a very mild soft bar with rich, creamy lather. Recommended usage rate is 5-20%. Sweet almond oil saponifies easily, but does not accelerate trace.
Shea butter
Shea (karite) butter is one of the most valuable skin conditioners. It is very stable and does not spoil easily. It makes a very hard bar of soap with great conditioning and moisturizing properties and creamy lather. Shea butter is considered a luxury butter in soap making. Recommended usage rate is 5-15% or even higher, always with good results. Shea butter accelerates trace. It is often used for superfatting by adding at trace.
Cocoa butter
Cocoa butter is hard and brittle at room temperature and melts at 34-38oC (93-100oF). It makes a very hard bar with rich, creamy lather. Also, it moisturizes and softens the skin and has good conditioning properties. Recommended usage rate is 5-15%. At higher rates, cocoa butter will make a brittle bar of soap. It can accelerate trace.
Safflower oil
Safflower oil makes a white, soft soap bar with stable lather and good conditioning and moisturizing properties. It traces slowly, so it is good for complicated swirling. Safflower oil in soap making is similar to sunflower, soybean and canola oil and can substitute a portion of olive oil in the recipe. It has a short shelf life. Recommended usage rate is 5-15%.
Sunflower oil
Sunflower oil is liquid at room temperature and makes a white, soft bar of soap. Sunflower oil contributes to highly moisturizing properties and rich, creamy lather. It is rich in polyunsaturated fatty acids which yield a conditioning soap bar that is prone to rancidity and DOS (dreaded orange spots). Recommended usage rate is 5-20%. Sunflower oil is sometimes considered a cheaper alternative to olive or almond oil. It saponifies slowly, so it is good for swirling recipes.
Tallow
Tallow is the most important soap-making fat in history. It makes a very hard, white, highly moisturizing and conditioning bar of soap with stable, creamy lather and mild cleansing properties. Tallow is one of the best tracers in soap making. Recommended usage rate is up to 40%, but basic tallow soaps are often made of 85% or more tallow. If used in higher rate, the soap bar may become brittle.
Lard
Lard is another historic source of fat for soap making. Lard makes a hard white bar with low, stable but slimy lather. Lard soap has moderate cleansing, conditioning and moisturizing abilities. It is a good soap filler due to its low price and the fact that qualities of lard soap can be easily improved with the addition of other oils. Lard can be used in any rate, usually up to 50%. Soap made of 100% lard and 0% superfat is actually the traditional laundry soap.
Avocado oil
Avocado oil is a luxury emollient oil in soap making. It makes a soft soap with stable, creamy lather and mild cleansing properties. Nevertheless, it is very conditioning and moisturizing to the skin due to its high content of oleic acid and unsaponifiables. Recommended usage rate is 5-20%, but it is often used at an even higher rate. Avocado oil does not accelerate trace.
Mango butter
Mango butter is a semi-solid, off-white oil resembling shea or cocoa butter. It makes a hard soap bar with stable and very conditioning lather. Its high unsaponifiable content provides beneficial skin care properties. Recommended usage rate is 5-15%.
Canola oil
Canola oil makes a soft soap bar with great conditioning and moisturizing properties and low, creamy lather. It is a great substitute for olive oil. Recommended usage rate is 10-15%. Canola oil slows down trace, so it is good for complicated swirls.
Corn oil
Corn oil is not regularly used in soap making, but it can be added as part of liquid oils. It contains a high portion of polyunsaturated fatty acids which makes it a good conditioner and leads to quick rancidity. Corn oil makes creamy, white soft soap with low or somewhat slimy lather and good conditioning and moisturizing properties. Recommended usage rate is 10-15%. It saponifies slowly, so it is good for swirling recipes.
Grape seed oil
Grape seed oil makes a creamy, white soft soap bar with low, creamy lather and excellent conditioning properties. It is a valued oil in skin care and, as such, used as part of liquid oils in soap making for a good reason. Its high level of polyunsaturated fatty acids leads to rapid rancidity, sometimes before the end of curing time. Recommended usage rate is 3-10%. Grape seed oil is a slow tracer.
Soybean oil
Soybean oil produces a soft, mild soap with low lather and good conditioning and moisturizing properties, but it tends to go rancid very quickly. It is frequently used as a cost-effective portion of liquid oils. Recommended usage rate is 5-20%. In the recommended dose and combined with hard oils, it contributes to mildness and moisturizing, stable lather. With higher dosing it increases the risk of rancidity. Soybean oil does not speed up trace.
Soap making waxes – in brief
Jojoba oil
By its chemical composition, jojoba oil is actually a liquid wax. It contains a rather high unsaponifiable content which makes jojoba one of the most valuable oils for skin care. Jojoba oil itself saponifies at low rate and slowly, it tends to separate and makes very soft soap with very low lather. In oil mixtures, it stabilizes existing lather and provides excellent moisturizing and conditioning qualities. Recommended usage rate is 5-10%. If used at higher rates, it will contribute to a soft bar and cut down lather. Jojoba oil accelerates saponification.
Lanolin
Lanolin is a fat-like wool wax. Due to its high content of waxy components, it does not saponify. Recommended usage rate is 1-5%. Lanolin accelerates trace, increases temperature in the mold and forces soap to gel. With recommended dosing, lanolin gives soap its excellent emollient and moisturizing qualities and a silky feel. Used at higher rates, it leads to a soft bar of soap.
Beeswax
Beeswax is a hard wax with a melting point of 58-64oC (136-147oF). This makes it tricky for use in the cold process. It is used to increase hardness, impart honey scent and prevent soda ash. Beeswax contains a high portion of unsaponifiables, so it saponifies at a very low rate but contributes to a hard soap bar with a silky feel. Recommended usage rate is 1-3%. At higher rates, it will inhibit lather.