The creation of genuine Marseilles soap is a complex process that requires several steps. First, oil is mixed with alkali and sea salt in a large cauldron. One cauldron can yield up to 8 tons of soap. Olive oil will produce a green-colored soap and copra with palm oils will make a white-colored soap. The mixture is made to reach boiling point and cooks for about 8 hours during which the chemical reaction of saponification creates the soap mixture.
The mixture is then cooked at 100°C for about 4 hours. During this time the soap maker must stir the mixture so that it does not boil over. He also regularly collects the rejected alkalis that accumulate on top of the mixture. At the end of this step, the mixture is washed with salty water to get rid of any impurities left behind. The soap maker tastes the mixture. If it is salty, he must wash it again. If it is sweet, it is ready and there are no soda byproducts left behind. The mixture is then covered and left to cool and dry for 36 hours.
The bottom of the cauldron is linked to cement compartments on the first floor. The mixture is poured slowly while it's still at 60°C into the cement basins and left to dry for 48 hours. When the soap is dry it is marked with a special compass in order to be cut into 35 kg blocks then into 2.5 kg bars then into 300g, 400g, 600g and 1kg cubes.
The soap is then stamped and left to dry on wooden boards with space in between the pieces. It takes up to 15 days to dry a bar of soap that is 1 cm thick. For fragrance Marseilles soap, the blocks are made into soap flakes. Fragrance is then added as the mixture is stirred. The soap is remolded into bars and left to dry. The last step is stamping of the soap. The soap maker uses an old hand press for traditional stamping of Marseilles soap.