Marseille soap or Savon de Marseille is a traditional hard soap made from vegetable oils that has been produced around Marseille, France, for about 600 years. The first documented soapmaker was recorded there in about 1370. By 1688, Louis XIV introduced regulations in the Edict of Colbert limiting the use of the name savon de Marseille to olive oil based soaps. The law has since been amended to allow other vegetable oils to be used.
By 1913 production had reached 180,000 tons, and in 1924 there were 132 soapmaking companies in the Marseille and Salon-de-Provence areas combined, but by 2000 only five remained.
Traditionally, the soap is made by mixing sea water from the Mediterranean Sea, olive oil, and the alkaline chemicals soda ash (sodium carbonate) and lye (sodium hydroxide) together in a large cauldron (usually making about 8 tons). This mixture is then heated for several days, stirring constantly. The mixture is allowed to sit until ready, then poured into a mold and allowed to set slightly. While still soft it is cut into bars, stamped, and left to completely harden. The whole process can take up to a month.
Today there are two main varieties of Marseille soap, a greenish hued made with olive oil and a white made of palm oil or a palm and copra oil mixture. Originally sold only in 5 kg and 20 kg blocks, today they come in sizes between 300 g and 1 kg, though larger sizes are often available, some up to 40 kg.