Where are soaps made

The cold process for soap production described here was documented by the Don Quixote working group. A worksheet is available for the hot process.


Safety regulationsn

When working with caustic soda are safety goggles, chemical resistant rubber gloves and a closed one Work smock to wear. Caustic soda splashes in the eyes or on the skin can cause severe burns. Wooden objects or table tops can be damaged by the caustic soda, so cover the surface well with paper. The mixture can swell and splash, especially during saponification. The pots must therefore be large enough and contain a lot of reserve space. The room should have a sink and be well ventilated. Towels and paper towels are always ready to wipe off soap or lye residue.

Soap production using the cold process 

The basic principle in soap production is that fats and oils are "saponified" with the help of caustic soda to make soap and glycerine. The simplest recipe for the production succeeds according to the so-called Cold process. After adding caustic soda to the fats and oils, the saponification process takes place at a relatively low temperature, i.e. initially at around 60 ° C and even at room temperature during the long ripening process. The disadvantage is that the actual saponification takes four to six weeks and only then is the soap ready. The soap is not salted out with table salt, which is why this process results in a high-quality soap in which the substances that care for the skin, such as glycerine, are retained. The method described here is popular with manufacturers who have enough time and want to produce a very high-quality product.

Soap production: addition of coconut fat and olive oil.

First, coconut oil and olive oil are heated in a stainless steel pan on a hotplate until the mixture has just melted. An aluminum pot must not be used under any circumstances, as this is attacked by the caustic soda. Then the stove is switched off and the pot is removed. The temperature should not exceed 80 ° C. The olive oil produces the nourishing component of the soap. The coconut oil makes the soap hard, so it can be stored well. Above all, saponification with caustic soda leads to self-heating of the mixture, so that a heating plate is no longer required. A high proportion of olive oil leads to a green soap, a high proportion of coconut fat (or palm oil) tends to produce a yellow one.

Start of saponification: addition of sodium hydroxide solution.
After the olive oil and coconut fat have melted, add the 32% concentrated sodium hydroxide solution at 40 to 60 ° C, depending on the coconut fat content, and stir vigorously until the mass thickens like a paste. The concentrated sodium hydroxide solution can also be prepared by carefully dissolving granular sodium hydroxide in water. At the now taking place Saponification the is formed according to the principle of neutral oil saponification Soap glue. The thickening process can be accelerated with the help of a hand blender so that it does not need to be stirred for more than half an hour.

Advanced saponification after stirring.


Other ingredients are added while it cools: linseed oil makes the soap finer and smoother, castor oil promotes the foam-forming effect of the soap and pure scented oils such as lavender oil give the product a pleasant scent. Perfumes are unsuitable because they change the scent of the finished soap or create streaks due to the alcohol present. Oils such as jojoba oil, avocado oil or wheat germ oil also have a nourishing effect. At the same time, you can also add shredded, organic material such as lavender flowers or dyes approved in cosmetics. Food dyes or pigments that subsequently discolor the skin are not suitable. After the addition, the mixture is stirred again. Adding the special oils accelerates the thickening process.


Prepare the special oils.

The porridge is placed in a wooden box pan that has been greased or lined with baking paper and covered with a tea towel. Wood has good insulating properties and is breathable at the same time. To prevent bubbles from forming, tap the mold vigorously or hit it on the table.

Transferring the soap glue into a wooden mold.

For post-ripening, some manufacturers place the mold in an oven preheated to a maximum of 90 ° C for a few more hours. The saponification process is an exothermic reaction that releases heat. Therefore, the temperature in the soap mass rises by itself, which can be measured with a thermometer. With an optimal reaction, the mass becomes more transparent and the soap goes into the Gel phase above. The "young" soap, which has not yet been completely saponified, contains a lot of caustic soda. Therefore the pH value with pH = 11 or pH = 12 is still too high. This would be harmful to the skin. The final ripening process therefore takes four to six weeks in a designated cupboard.

The “soap cake” matured after six weeks.

After the ripening process, the mold is loosened and the resulting soap cake is cut into manageable pieces. The subsequent ripening leads to the soap shrinking and drying out, at the same time the pH value drops to pH = 9 or below. This is how you get the high-quality, still glycerine-containing Glue soap.  

Cutting and sizing the finished soap.

Bewindow production after Hot process

At the Hot process the saponification process is accelerated by the additional supply of heat and water. When adding sodium hydroxide solution, the mixture then begins to swell and boil. Bubbles rise and foam forms on the surface. So that the soap does not burn at the bottom of the pot, it is traditionally heated in a water bath. You can do this by placing a smaller saucepan in a larger saucepan with boiling water. With the term Soapy water is generally meant the saponification process. However, the term is somewhat unfortunate because the saponification process in the pure cold process, in which the mixture does not boil, is also a "soap boiling" process. Whether a cold process or a hot process is involved cannot always be clearly decided. The self-heating during saponification in the cold process can be so strong that the hot process is used more or less involuntarily. The vigor of the reaction is mainly controlled by the proportions of the starting materials and the coconut oil. Before the soap makers could import the coconut oil, the hot process was widely used. Then they discovered that saponifying coconut oil generated enough heat to speed up the process.
At the Curd soap process table salt is added after the saponification process. Because of this Salting out the soap separates from the glycerine. While the educated Curd soap floats at the top, the glycerine-containing one forms at the bottom Lower lye. Glycerine is a valuable raw material and can be sold on. It is an important component of other cosmetics and it is used in the manufacture of nitroglycerin and dynamite. However, the soap loses an important, caring component.
Another advantage of salting out was previously seen primarily in the fact that undesirable pollutants and odorous substances remained in the lower lye. With the curd soap process in connection with the hot process, you could also work with more water and with diluted alkalis. This used to be important because the caustic soda was not available in concentrated form. The soap makers made the lye from soda and slaked lime. They received a contaminated lye with a concentration of a maximum of 20%.
The flocculated curd soap was then usually mixed with water again and salted out a second time. As a result of the repeated salting out, the curd soap separated completely from the water and impurities. The hot process in connection with the curd soap process used to be used primarily for the production of Fatty soap made from cheap animal fat waste such as lard or beef tallow.
Note: If you want to shape a bar of soap into a ball - as shown in the photos above in the school experiment - the curd soap must be salted out of the hot solution and shaped while it is warm (see> worksheet).

Production of Schmierseife

The two methods described above result in a tough one Soda soap. With them, the soap anion is linked to a sodium ion. At a Potash soap instead contain potassium ions. It is not firm, it feels greasy, which is why it is also known as soft soap.

To make it, coconut oil is melted in the same volume of water. Glycerine, in which a little potassium hydroxide is dissolved, is carefully added to the hot melt. Then heat and stir with the magnetic stirrer for at least five minutes until the mixture foams. After cooling, a greasy, yellow mass forms, which forms a foam when shaken with water. Soft soaps are mainly used for cleaning floors.

Questions of understanding

1. Show the difference between glue and curd soap!
2. What are the advantages and disadvantages of the curd soap process?
3. What process would you, as a hobby craftsman, use today to obtain a very high-quality soap? Explain!
4. Show the difference between a soda and a potash soap with a chemical formula.