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FULL BOILED, SEMI BOILED AND SWING SOAP
Industrial soap can be classified according to how glycerin is managed during saponification. Full Boiled, Semi Boiled and Swing Soap differ mainly in the way glycerin is separated or retained in the finished soap.
Full boiled and semi boiled swing soap comparison
Soap Types: Full Boiled, Semi Boiled and Swing Soap
In industrial soap manufacturing, solid soaps can be classified according to the saponification process and the way glycerin is handled during production. Three terms commonly encountered in the soap industry are Full Boiled Soap, Semi Boiled Soap and Swing Soap. The main difference between these soap types is whether the glycerin naturally produced during saponification is removed from the soap or retained in the finished product.
Full Boiled Soap
Full Boiled Soap is produced through a saponification process in which the glycerin generated by the reaction is largely separated from the soap. The process can be carried out using a kettle saponification plant or a continuous saponification system with a washing section. During the process, the soap is separated from the glycerin-containing aqueous phase. As a result, the finished soap contains only a relatively small amount of residual glycerin. Full boiled soap has traditionally been used as a base for the production of high-quality toilet soap and laundry soap, depending on the formulation and subsequent finishing process. The main characteristic of this process is therefore:
Glycerin produced → separated during processing → very small % of glycerin in finished soap
Semi Boiled Soap
Semi Boiled Soap is produced without a dedicated glycerin separation stage. The saponification of oils and fats takes place using sodium hydroxide, producing soap and glycerin. Because the glycerin is not removed through a washing and separation stage, a significant portion remains in the soap. The glycerin remains in the soap in the range of approximately 6–8%, although the actual amount depends on the raw materials, formulation and manufacturing process. Semi boiled soap can be produced using batch saponification or continuous systems without a washing section. Historically, semi boiled soap was mainly associated with laundry soap, but the process can also be used for certain toilet soap formulations. One important advantage is that fewer processing stages are required compared with a traditional full boiled process, which can reduce equipment requirements, processing time and production costs. The main characteristic is:
Glycerin produced → not separated → retained in the soap
Swing Soap
Swing Soap is a more recent term used in the soap industry. The name comes from: SWING = Soap With INside Glycerine. The term describes soap in which the glycerin produced during saponification remains inside the soap rather than being removed through a glycerin separation stage. From a practical point of view, Swing Soap and Semi Boiled Soap describe essentially the same fundamental concept: glycerin is retained in the soap. The term “Swing Soap” is therefore mainly used to emphasize the presence of glycerin inside the finished soap.
Glycerin and Soap Quality
The presence or absence of glycerin should not automatically be interpreted as an indication of soap quality. The final characteristics of a soap depend on many factors, including:
  • fatty-acid composition;
  • Total Fatty Matter (TFM);
  • moisture;
  • glycerin content;      
  • fillers and additives;
  • manufacturing process;
  • finishing technology.
A semi boiled or Swing soap can therefore be formulated to produce a consistent and commercially suitable finished product. The key difference is primarily related to process design and glycerin management, rather than simply to whether one type of soap is “good” and another is “bad”.
Why Glycerin Separation Matters
Glycerin is a valuable by-product of soap manufacturing. In a full boiled process, the glycerin-containing phase can be separated from the soap and subsequently processed for glycerin recovery and purification. In a semi boiled or Swing process, the glycerin remains incorporated into the soap. This difference has consequences for both the manufacturing process and the final soap composition. For manufacturers, the decision to separate or retain glycerin is therefore an important part of selecting the appropriate industrial soap manufacturing system.
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