The cold process is quick & simple (takes a few hours) and is used for home-made soap. The heated process is more elaborate and has been the one used in the past to make soap industrially. The Patounis Soap Works factory is one of the few remaining factories in the world that still uses the traditional heated process to make soap.
The heated process has two important advantages. It separates the soap from non-saponifiable elements (ie glycerin) and it offers fine control of the pH. Both these lead to much purer & better soap. They also lead to a much more elaborate & sensitive process - Mr Patounis himself admits that it took him years to master it to perfection!
The only ingredients used by Mr Patounis are (the) oil, soda, sea salt and water. The ingredients are first heated in the kettle for one week. The produced liquid is then put in flat casts for another week where it solidifies and it is cut into bars (natural food dye is used to mark the surface for cutting). Because the fresh soap bars are still too soft to be used, they are placed on drying racks for four months. A final couple of weeks is spent for quality assurance and packaging. So it takes almost 5 months for a bar of natural soap to be ready for use!
Once ready, our soap consists almost entirely of saponified oil and water (there are also traces of sea salt and olive residues from the process). At packaging time the water content is usually no more than 10% - the rest is pure soap. It simply cannot get more natural than this! Because it is a natural product, water keeps evaporating, the soap becomes more dense, and the color changes.
Click here to watch a short (6-minute) video of Mr Patounis explaining the process of traditional olive soap making at his historic soap factory.