Olive oil is mixed in large cauldrons with an aqueous solution of an alkali - soda ash. Originally the soda ash was obtained from a desert plant, the salsola kali. But recently this has been replaced by industrially produced soda ash.
The mixture is heated to more than 200 degrees Celsius and stirred until the oil fully decomposes yielding glycerin and the sodium salt of olive oil. This process is called ‘saponification’. Towards the end of the initial process, bayberry oil is added to the mixture and further saponification takes place.
The caustic soda solution is drained from the cauldron and the soap mixture is washed with fresh water until tested free of any alkalinity. It is drained again and left overnight to slightly cool and to further drain excess water.