In soaps, there are a variety of ingredients used for different purposes. Starting with the basic formula, alkalis are used for mixing with oils to make the basic soap. Alkalis also enhance surfactants, neutralize acidity in other ingredients, and increase the alkalinity of the final product. Examples are lye (made of plant ashes and used in natural soaps) and sodium carbonate (used in some commercially-produced soaps).
Abrasives are often added to soaps with the purpose of refining or smoothing skin. Coarser particles are for purposes like softening the feet, while very fine abrasives can be used on the face. Examples of natural abrasives are ground peach cores, sugar, and salt crystals.
Antimicrobial agents are added to many types of soap now, including dish soap and hand soaps. These antimicrobial products kill germs and inhibit the growth of germs on the soap and on the area washed. Triclosan is an example used in commercial production, with pine oil used in natural antibacterial soaps.
Colorants are added to make the soap attractive. Natural soaps often make use of food coloring to create aesthetically pleasing bars of soap for home use. Fragrances are also for the senses. Some are meant to sooth, like lavender, while others energize, like citrus.
Preservatives are used in commercial production of soap for preventing discoloration, oxidation, and/or bacterial growth. Examples are butylated hydroxytoluene and glutaraldehyde. Natural soaps do not usually have the years of shelf life commercial soaps do, but they do not contain chemical preservatives. Instead, natural soaps are generally made in fresh batches and purchased by consumers as they are used.
