Traditional cold soap and hot soap are both fatty acid soaps with fatty acid salts as the main surfactants. The pH value of fatty acid soap is alkaline, with strong degreasing power, and the skin feels tight after washing. Long-term use will make the stratum corneum thinner, causing great irritation and harm to the skin, and when used in hard water, it will react with calcium ions to form insoluble calcium soap.
With the improvement of people's living standards, many changes have taken place in the field of soap. First of all, liquid products such as shower gel, shower gel, hand sanitizer and facial cleanser are widely used. Secondly, more and more soap-free cleaning blocks and so-called composite soaps, that is, soap and surfactant composite products, have entered people's homes, and these products have gradually entered the original market share of soap.
Neutral soap is a composite soap with synthetic surfactant as the main body and contains no free alkali. The weak acidity, which can be neutral or the pH value is lower than 7, can be adjusted to solve the problem that soap is not suitable for alkalinity. It foams and cleans well under various water hardness conditions, and will not form curd or precipitate.
The historical development of soap
A synthetic detergent appeared in Song Dynasty, which was made of natural Gleditsia sinensis (also known as Gleditsia sinensis, hanging knife and Gleditsia sinensis) by mashing and grinding, adding spices and other things, and made into orange-sized balls for washing face and bathing body, commonly known as "soap balls". Song people's careful "Old Wulin Stories" (Volume 6) and "Little Broker" recorded that there was a businessman who specialized in "soap troupe" in Lin 'an, Kyoto in the Southern Song Dynasty.
Li Shizhen's Compendium of Materia Medica in the Ming Dynasty recorded the making method of Gleditsia sinensis: Gleditsia sinensis was born in a high mountain, with tall trees, leaves like sandalwood Gleditsia sinensis, flowering in May and June, the pod was three or four inches thick, fleshy, with several spots as big as fingers, not round, and white kernels inside, which were edible. Picking pods in October, boiling and mashing, white flour fragrant pills, bathing the body surface, removing dirt and moistening, is better than Gleditsia sinensis. In addition to natural plants such as Sapindus mukoraiensis, it is also circulated among the people and has become a good cleaner.