Soap Making Glossary
Quick definitions for common soap making and calculator terms.
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Core Soap Making Terms
Lye
A strong alkali used to turn oils into soap. In soap making this usually means sodium hydroxide or potassium hydroxide.
Sodium Hydroxide
Also called NaOH. Used for bar soap. It is caustic and must be handled with proper safety gear.
Potassium Hydroxide
Also called KOH. Commonly used for liquid soap because it creates a softer soap paste.
Purity (Lye Purity %)
Lye may be sold below 100% purity, especially KOH. Lower purity means you must use more lye by weight to reach the same active alkali amount.
Cold Process
Soap made by mixing oils and lye solution, then pouring into a mold to finish saponification and cure over time.
Hot Process
Soap made with additional heat during saponification, usually resulting in a rustic texture and faster initial usability.
Melt and Pour
A pre-made soap base that is melted and customized. No direct lye handling is required by the maker.
Trace
The stage where soap batter thickens and leaves a visible trail when dripped on itself. Light trace is often ideal for pouring.
Gel Phase
A warm stage where soap becomes translucent and gel-like. It can deepen color and create a more uniform look.
Superfat
The percentage of oils left unsaponified on purpose, often used to make soap feel milder.
Lye Concentration
The percentage of lye in the lye-water solution. Higher concentration means less water.
Water:Lye Ratio
The amount of water used relative to lye (for example 2:1). It affects batter speed and curing behavior.
Water Discount
Using less water to speed unmolding and dry-down. This can shorten working time and cause faster thickening, so it is often used carefully.
Full Water
Using more water for longer working time and easier fluid designs. Bars usually take longer to unmold and cure.
Saponification
The chemical reaction between fats/oils and lye that creates soap and glycerin.
SAP Value
The amount of lye needed to fully saponify a specific oil. Different oils have different SAP values.
Cure
The resting period after unmolding and cutting, when water evaporates and bar structure improves.
CPOP
Cold Process Oven Process. A method of warming molded cold process soap to encourage full gel phase.
Gel / No Gel
Gel phase can deepen colors and change texture. No-gel soap is often more opaque and pastel-looking.
Soap Qualities
Hardness
A prediction of how firm a bar will be. Higher hardness generally means a firmer, longer-lasting bar.
Cleansing
Indicates how strongly a bar removes oils from skin. Too high can feel drying for some users.
Conditioning
Indicates how gentle and skin-feel friendly a bar may be, often associated with more unsaturated fatty acids.
Bubbly
A prediction of larger, airy lather bubbles.
Creamy
A prediction of dense, lotion-like lather.
Iodine
A value related to unsaturation of oils. Higher values can correlate with softer soap and faster oxidation risk.
INS
A rule-of-thumb index based on SAP and iodine values. Higher INS often means harder, more cleansing (potentially more drying) bars.
Fatty Acid Profiles
Lauric
Contributes cleansing power and bubbly lather; high levels can feel drying. Example high source: coconut oil.
Myristic
Adds cleansing and bubbly qualities similar to lauric, usually with added hardness. Example high source: coconut oil.
Palmitic
Supports bar hardness and stable, creamy lather. Example high source: palm oil.
Stearic
Increases hardness and dense creamy lather, often helping bar longevity. Example high source: cocoa butter.
Ricinoleic
Boosts lather stability and can improve conditioning feel; commonly associated with castor oil. Example high source: castor oil.
Oleic
Promotes conditioning and mildness, but very high levels can produce softer bars. Example high source: olive oil.
Linoleic
Adds conditioning and silkiness, though excessive amounts may reduce shelf stability. Example high source: sunflower oil.
Linolenic
Contributes conditioning, but high levels can increase softness and oxidation risk. Example high source: flaxseed oil.
Troubleshooting
DOS (Dreaded Orange Spots) / Rancidity
Orange spots or off odors caused by oxidation of fats. Risk rises with old oils, high unsaturated profiles, heat, light, and contamination.
Acceleration
Batter thickens faster than expected, often from fragrance choice, warmer temps, or recipe composition.
False Trace
Apparent thickening caused by cooling fats rather than true emulsion. If poured too early, batter can separate.
Overheating / Volcano
Soap gets too hot and may crack, dome, or erupt out of the mold. More common with sugar, milk, high heat, or heavy insulation.
Additives and General
Sugar
Often used in small amounts to boost bubbly lather. It can increase heat, so many makers dissolve it fully before mixing.
Clay
Used for slip, feel, and appearance. Clay can also thicken batter depending on type and usage rate.
Chelator
An additive such as sodium citrate or EDTA that binds minerals to reduce soap scum and help lower oxidation risk.
Additives
Extra ingredients added for performance or aesthetics, like clays, sugars, salts, and colorants.
Batch / Yield
The total amount of soap produced by a recipe. Final cured weight is lower than fresh weight because water evaporates during cure.
Lather
The foam character of soap, including bubbly and creamy traits. It depends on fatty acids, cure time, additives, and water quality.
Hard Water
Water high in calcium and magnesium that can reduce lather and create soap scum. Chelators can improve performance in hard water.