Soap making process

The basic chemical reaction of soap is the interaction of oil and alkali to form soap and glycerin.


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The soap obtained by the reaction is salted out, washed, and finished, and is called a soap base, and further processed to form soaps of various commercial forms.


Remove impurities from grease. Common refining processes include deodorization, alkali refining (deacidification) decolorization. Degumming is a hydration method in which a colloid such as a phospholipid in a fat or oil is removed, a colloidal hydration such as a phospholipid is hydrated with water, and then precipitated and precipitated; and a phospholipid and a similar impurity are carbonized and precipitated by concentrated sulfuric acid. The main function of alkali refining is to remove free fatty acids in fats and oils, but the formation of flocculent soap removes pigments and impurities in fats and oils by adsorption.


After the oil is refined, it is saponified with a base. Boiling is the main method of saponification, and the soap pot is cylindrical or square.

In addition to the conveying pipe with grease, lye, water, salt water, etc., it is also equipped with a direct steam or steam coil to pass steam and stir the soap. The pan is also equipped with a moving head tube, and the upper mouth of the tube can be placed at any liquid level to discharge the soap in the pot. The bottom of the pot is tapered, and a discharge tube is arranged to discharge the residual liquid remaining after the discharge of the moving head tube. The oil and caustic soda are boiled in the soap pot until the saponification rate reaches about 95%, and the saponification operation is stopped when the soap material is uniformly closed.

Salting out

In the closed soap, salt or saturated brine is added to separate the soap from the dilute glycerin water. The lowest concentration at which soap is precipitated is called the salting out limit concentration. After the closed soap gel is salted out, the upper layer of soap is called soap granules; the lower layer of salted glycerin water is discharged from the bottom of the soap pot to recover glycerin.


After separating the waste liquid, water and steam are added to boil the soap particles, so that they are separated into a uniform soapy gel, and the residual glycerin, pigment and impurities are washed out.

Alkaline analysis

In order to completely saponify the oil and fat remaining in the soap granules, glycerin, salt, coloring matter and impurities in the soap granules are further washed out by alkali precipitation. The concentration of the lowest alkali in which the alkali water is completely precipitated is referred to as the alkali precipitation limit concentration.

Finishing and adjusting the electrolyte and fatty acid content in the soap after alkali precipitation, reducing impurities, improving the color, and obtaining the maximum soaping rate and quality of the soap base. When finishing, add appropriate amount of electrolyte (such as caustic soda, salt), and adjust enough to separate the soap material into two upper and lower soap phases. The upper layer is a pure soap base and the lower layer is a soap base. Soap feet have deep color and many impurities, and are generally reused in the next pot of alkali precipitation.


The soap base is condensed into a large soap board, and then cut into soap slabs, printed and dried into laundry soap, soap and other products.

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