Jun. 15, 2022
Soap is a cleaning agent made by mixing alkaline substances with fats. The product is very effective at removing oils and fats from surfaces such as skin, fabrics, and floors. A variety of ingredients can be used to make soap, and the type of ingredient determines the properties of the final product.
In the early days of the United States, soap was made by mixing lye solution with animal fats. The lye solution was made by soaking hardwood ashes in water and then filtering out the ashes. This highly caustic solution was mixed with saved cooking fat and stirred over an open fire for several hours. The resulting soap is used for various types of cleaning tasks.
Soap is made by mixing an alkaline substance with fat in a chemical process called saponification. The alkali reacts with the fatty acid to produce a long molecule that is hydrophobic (water-repellent) at one end and hydrophilic (water-loving) at the other. This molecular structure gives the soap its cleaning properties. The hydrophobic end is attracted to oils and greases, while the hydrophilic end is attracted to water molecules. Mixed together, the soap pulls the oil into very small balls, creating a suspension of oil and water that is easier to wash off from surfaces. Benzaldehyde can be directly added to perfume, soap, food, beverage, and other products. It is widely used in the production of derivatives, as well as in the perfume and flavor industries.
Lye is the most common lye used in soap making. The chemical name for lye is sodium hydroxide. Another type of lye is potassium hydroxide, also known as potash. The type of lye used affects the final properties of the soap product. For example, potash lye tends to make soap that is softer, while lye tends to make soap bars that are harder.
Many different types of animal and vegetable fats can be used to make soap. Traditional soap makers use animal fats (lard or tallow) saved from cooking and slaughtering. However, there are a variety of vegetable fats that can be used instead. These include coconut oil, peanut oil, almond oil, palm oil, olive oil and soybean oil. The different fatty acids in these natural oils give soaps their different properties and textures. The long-chain fatty acid molecules in lard make the soap very hard and somewhat insoluble in water (lather). The shorter fatty acid molecules in coconut oil make the soap softer and more latherable. Different oils can be blended to make soaps with the desired softness and lathering properties.
Other ingredients are often added to enhance soap products. Natural skin care ingredients such as aloe vera, honey, and oatmeal may be added. Often, perfumes and fragrances are added. Preservatives may also be added to extend the life of the soap bar.
Detergents are chemically different from soap.
The terms soap and detergent are often used interchangeably. However, detergents have different chemical properties. One disadvantage of soap is that soap scum is produced when soap is used in hard water. Soap combines with calcium and magnesium in hard water to form an insoluble precipitate that drips from the solution onto the nearest surface. Detergents have a different molecular structure and do not precipitate with calcium and magnesium, thus avoiding the dreaded bathtub ring.