Soap is made from fat through a chemical process called saponification. This involves reacting a fat (like animal tallow, lard, or vegetable oils) with an alkali, most commonly sodium hydroxide (lye). The lye is highly corrosive, but the reaction with the fat neutralizes it, creating soap.
The Saponification Process
- Fat Selection: Various fats can be used, including animal fats (tallow, lard) and vegetable oils (olive oil, coconut oil). Historically, readily available animal fats were frequently used. Even fats unsuitable for cooking were utilized. [Source: How to Make Lard Soap Cheaply the Old-Fashioned Way, Making Bacon Soap]
- Mixing with Alkali: The chosen fat is mixed with a strong alkali like sodium hydroxide (lye). This mixture is crucial for the chemical reaction. [Source: As we mentioned, soap is made from a chemical reaction between a fat and an alkali ingredient. Tallow soaps are made by mixing animal fat with sodium hydroxide, more commonly known as lye.]
- Saponification Reaction: The lye reacts with the triglycerides in the fat, breaking them down into glycerol and fatty acid salts. These salts are what constitutes soap. [Source: As we mentioned, soap is made from a chemical reaction between a fat and an alkali ingredient. Tallow soaps are made by mixing animal fat with sodium hydroxide, more commonly known as lye. Lye is highly corrosive, but when it mixes with tallow it undergoes a reaction called saponification.]
- Soap Formation: After the reaction, the mixture is processed (often involving cooling and curing) to separate the soap from the remaining glycerol. [Source: Simple Tallow Soap Recipe, Tallow Soap Recipe]
- Product: The resulting product is soap, a mixture of fatty acid salts that possess cleaning properties. [Source: Soap - Wikipedia]
Types of Soap and Fats Used
Both bar soap and liquid soap can be made using animal or vegetable fats. The choice of fat affects the soap's properties. For example, tallow soap, made from animal fat, is often praised for its hardness and cleansing power. [Source: Is it true that soap bars contain animal fat but liquid soap does not, Sodium Tallowate: What It Is and Why It's Sometimes Used in Soap, 100% animal fat? ] Modern soap-making often utilizes a blend of different fats and oils to achieve desired characteristics. [Source: How to make a handmade soap bar using BSFL fat]
How Soap Works
Soap molecules have a dual nature. They possess a hydrophilic (water-loving) and a hydrophobic (water-fearing) end. This allows them to emulsify oils and fats, lifting them from surfaces and allowing them to be washed away with water. [Source: ELI5: how does soap remove fats and oils if it's made of fats and oils]
