How to Make Homemade Soap: Easy Terms You Should Know

A Soap-Making Resource and Glossary

How to Make Homemade Soap: Easy Terms You Should Know

Even with easy homemade soap recipes, beginners get bombarded with foreign terminology. Use this glossary if you’re wondering how to make homemade soap easy. Soap-making resources make the process more enjoyable.

Soap: A salt created when a fatty acid meets a strong alkaline solution. This creates a surfactant, which breaks the surface tension of water so it can lift away dirt and oil. Soap can also be a verb referring to the process of soap-making. As in, “Don’t bother me for an hour. I’m soaping.”


Alkaline: Having a pH greater than 7. The opposite of an acid. Lye and potash are both alkaline.

Carrier oil: A base oil used to dilute essential oils. If you’re just learning soap-making techniques with scents, research your carrier oil to be sure it doesn’t react with allergies or use pure essential oils.

Cosmetic Grade: A quality high enough to be safe for cosmetics or application onto skin. Always use cosmetic grade colorants and fragrances for soap.

Essential Oil: Volatile oils from plants which possess the odor and other characteristics of the plants. Essential oils are often used in perfumes or pharmaceuticals.

Fatty Acid: Acids consisting of a long hydrocarbon chain ending in a carboxyl group bonding with glycerol to form a fat. Animal fats and plant oils contain fatty acids. They are essential for learning how to make soap with glycerin because natural glycerin is a byproduct of saponification.

Flash Point: The temperature at which an oil ignites. Oils with low or medium flash points may require special shipping and handling.

Fixative: A substance that slows evaporation. Soap-making fixatives sustain the fragrance longer within the product.

Fragrance Oil: Oils which may contain some or no essential oil but are used to scent soaps and candles. Always use cosmetic-grade fragrance oils for soap.

Glycerin: A colorless, odorless, sweet liquid with a molecular formula similar to sugar. Homemade soap retains natural glycerin but it has been removed from commercial detergent bars.

Hydrogenated Oil: Trans-fatty acids which have been chemically changed to be solid at room temperature. Shortening is hydrogenated but olive oil is not.

Litmus Paper: Paper used to test the acidity or alkalinity of a product.

MSDS – Material Safety Data Sheet: the paper which accompanies chemicals and states their physical states, toxicity, reactivity, and health effects. You can look up the MSDS for lye or potash online.

Potassium hydroxide (POH) – caustic potash: A caustic chemical, usually a white powder or pellets, used in soap-making. Potassium hydroxide is necessary for making liquid soap.

Render: The process of melting down raw animal fat for a usable product such as tallow or lard. Fat from a pig must first be rendered before the lard can be used for soap.

Saponification value (SAP): The milligrams of potassium hydroxide necessary to turn one gram of oil into soap. Each oil has its own saponification value. Good soap calculators also have settings for sodium hydroxide.

Sodium hydroxide (NaOH) – caustic soda – lye: The caustic chemical most commonly used by people learning how to make homemade soap. Easy to measure with a constant alkalinity, it produces a solid bar.

Tallow: Fat from bovine animals which has been rendered to a solid fat which is solid at room temperature. Tallow was traditionally used for soap and candles in Europe before olive oil came into fashion.

Vegan: Materials which have never been derived from animal products. Olive and coconut oils are vegan but honey and goat milk are not.

Viscosity: The property of a fluid that resists the force tending to cause the fluid to flow. Thickness. Viscous oils may need to be heated or melted prior to soaping.

Volatile Oils: A distilled oil which does not saponify. Oils which evaporate rapidly and are not glyceride. Many essential oils are volatile.

Photo by Shelley DeDauw


Cold process: A soap-making method which does not involve heat other than melting solid oils or warming liquid to a specific low temperature. Cold process takes longer than hot process but allows more artistic designs.

CPHP (Crock Pot Hot Process): A soap-making method where oils and lye are heated within a crock pot then cooked until the mixture reaches gel stage.

CPOP (Cold Process Oven process): A soap-making method where oils are unheated or warmed until melted then mixed with lye. Poured soap is placed within a warm oven to force the gel stage.

Cure: The time period where finished soap sits in a cool, dry, ventilated environment so excess water can evaporate. This makes the soap milder, harder, and longer-lasting

Gel: The active saponification phase where the soap mixture heats up and resembles petroleum jelly.

Hand-Milled: Grated or ground down by hand. Also called “rebatching.” Hand-milled or French milled soaps have been made and cured prior to grinding down and melting with a little water. Hot, melted soap is then remolded and cooled.

Hot Process: A soap-making method where oils and lye are mixed then actively cooked until it reaches the gel state. Hot process is the oldest soap-making method and allows for small discrepancies in alkalinity.

Lye Discount: A factor in a soap recipe where the amount of lye necessary is reduced. This creates a higher oil percentage to ensure soap is moisturizing and not dangerous. Most lye discounts range from 5% to 20%. “Superfat” can be used for the same concept.

Melt and Pour: A petroleum-based and commercially made product designed to be melted and cooled repeatedly for easy crafting projects. It’s how to make soap without lye or glycerin but it isn’t at all natural.

Morph: Change shape or form. Due to the alkalinity of homemade soap, fragrances may be altered or dyes may discolor. Learn which fragrances and colors morph by visiting soap-making forums.

OHP – Oven Hot Process: A soap-making method where oils and lye are combined then are cooked within an oven until the mixture reaches gel phase. This method isn’t frequently used by crafters knowing how to make homemade soap; easy CP or CPHP methods are preferred.

Rebatch: Also called hand-milling, this involves grating down previously made soap then melting it with a little liquid prior to cooling within soap molds. Rebatching is recommended to fix ugly soap or use scraps but cannot correct bad recipes.

RTCP – Room Temperature Cold Process: A soap-making method where oils are not heated at all prior to mixing with water and lye. RTCP is best for oils which are already liquid, such as olive or fractionated coconut.

Saponify: To convert a fat into soap by using an alkaline solution.

Seize: A physical reaction when raw, liquid soap suddenly hardens. This is most frequently caused by water discounts or adding specific essential oils and fragrances, such as some florals or fruity scents. To learn which fragrances cause seizing, visit soap-making forums.

Trace: The stage during soap-making where the consistency resembles thin pudding. When a spatula or immersion blender is lifted from the soap “batter,” it leaves a “trace” visible at the top of the liquid. Prior to trace, any drops immediately sink back into the mixture.

Water Discount: A factor in a soap recipe where less water is used than is recommended within a safe recipe. A water discount reduces cure time but can also lead to a false trace or seizing within the pot. Do not calculate in a water discount if you are just learning how to make homemade soap. Easy mistakes happen fast.

Zap: The effect, resembling electric shock, when a tongue is touched to soap that has not completely saponified. Soap-makers often use the zap test to determine if their product is safe. If soap is properly made, zap should only occur within a couple days of processing.


Cleansing: The ability of a soap to lift away dirt and oil. A balanced soap recipe should not be too cleansing or it will make skin too dry. Laundry soap should have high cleansing properties.

Conditioning: This refers to the soap’s emollient content, which helps skin retain moisture and stay soft. Soaps with higher conditioning properties are moisturizing but may cause acne in some people.

DOS – Dreaded Orange Spot: A primary indication of rancidity within soap. DOS begins with a small rusty orange dot, often at the bottom of the bar, which spreads as the soap goes bad. Soap with DOS is still safe to use. But please, for the reputation of all soap-makers everywhere, do not sell soap prone to DOS.

Emollient: A substance which softens and smooths skin. Many soaps and lotions are emollient or contain additional emollients.

Hardness: A soap quality which refers to a bar’s rigidity. Soaps with a lower iodine value are often harder.

Humectant: A substance which helps moisture absorb into the skin. Honey is a humectant often added to soaps and lotions.

INS: A theory developed in the 1930s to determine soap quality, taking into account the degree of unsaturation and molecular weight of the oil. The theory claims that a value of 160 equals perfect soap. Modern soap-makers often dispute the theory and instead lean on individual properties of a finished bar.

Irritant: A substance which causes reddening, discomfort, or allergic reactions within any of the senses. Commercially made detergent bars and perfumes contain more irritants than homemade soap does. Avoid irritants by combining pure oils with lye and avoiding colorants or fragrances.

Lather: The bubbles created when soap is agitated under water. Though lather is not necessary for a good bar of soap, the aesthetic quality is highly sought after. Soap-makers often add a percentage of coconut oil into recipes to add to the lather.

pH: The acidity or alkalinity of a chemical, on a scale of 0 to 10. Pure water is neutral. Numbers below 7 are acid and above 7 are alkaline (base). Very strong acids and bases can drop below 0 and above 14. Soap should be either neutral or slightly acidic.

Photosensitizer: A substance which makes the skin sensitive to sunlight. Some citrus essential oils can make the skin more prone to sunburn.

Rancid: Spoilage of an oil, characterized by a bad fragrance, darkening, and changes in viscosity. Because soap is made with oil, it can go rancid. Soap made with certain oils or a higher superfat are more prone to rancidity.

Superfat: The percentage of oil above what is necessary for saponification. A superfat percentage is often calculated to make soap more moisturizing or to avoid having too much lye in a recipe. The concept can also be called a “lye discount.” Common superfat percentages range from 5 percent to 20 percent.

Surfectant: A substance which breaks the surface tension of water, allowing it to carry away dirt and oil. Antibacterial soaps are usually unnecessary because surfectants allow bacteria to wash away with the oil.

Use this resource when learning how to make homemade soap easy. Easy glossaries help you focus on the important details such as safety precautions or procedures.

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