MANUFACTURING / Pot boiling method

The raw materials for soap are natural fat and oil, and caustic soda. Fatty acid, which is a part of oil and fat, bonds with sodium, which is a part of caustic soda, to create soap (fatty acid sodium). The nature of the soap-- how well it dissolves in water, how well it cleans, how much lather it produces--is determined by the type of fatty acid. Matsuyama makes its soap body from a combination of beef tallow and coconut oil.

  • The oil and fat are heated in a pot, stirred, and then combined with a caustic soda (sodium hydroxide) solution, which breaks down the oil and fat molecules into fatty acid and glycerin. The fatty acid bonds with sodium, and soap is produced. This process is called "saponification." We refer to it as the "Pot boiling method" (saponification method), and it is a traditional method of soap-making.

  • Inside the pot is a mixture of soap, glycerin, free fatty acid and free alkali. When sodium chloride is added, the soap molecules consolidate and non-soap materials precipitate together with the salt. This chemical reaction is called "salting out" and it is used to increase the purity of the soap. For its salting out process, Matsuyama uses natural salt (Ako salt).

  • After salting out, the heating and stirring of the pot are halted, and the process goes into "still standing" to allow the purity of the soap to increase in the pot. Then, the best quality soap from the top of the pot is skimmed off and put in a storage tank. The tank supplies soap body for both milled soap and framed soap.