How do you make soap?
Triglycerides have three fatty acid chains attached to a glycerol. Each type of oil has a different make up of fatty acids which results in soap with different properties. When creating a recipe I always have the end in mind, choosing oil and butter combinations that balance hardness, bubbliness, lather, and cleansing and conditioning abilities.
Sodium hydroxide, or lye, is a man made caustic base that is a necessary ingredient for the chemical reaction that produces bar soap. Without lye, you do not have soap.
Saponification, the chemical reaction achieved by adding lye to the fats, releases the glycerol from the long chain fatty acids. The glycerol (glycerin) remains free while the long chain fatty acids and lye combine and transform into soap.
Glycerin is a natural humectant that draws moisture from the air to your skin. Many commercial soap companies remove the glycerin from their soap for use in more expensive products, leaving a bar of soap that dries out your skin.
How does soap work?
Soap molecules are unique in that they have two ends with opposite feelings toward water. One end is hydrophilic, meaning it loves water, while the other end is hydrophobic, meaning it's repelled by water. The 'phobic' end attaches itself to whatever it can find that's not water, i.e. germs, grease, oil and dirt particles. The 'philic' end meanwhile reaches out into the water. As a result the germs, grease, oil and dirt get pulled away from your skin, surrounded by more soap molecules, suspended in the water and rinsed down the drain.