The cauldron cooking of Marseille soap paste at 212 or 230°F (100 or 110°C) makes its particularity. This old, long, and delicate method guarantees the final quality and longevity of the soap that cooks slowly for several days until the sodium hydroxide no longer alters. The soap master tastes the soap and checks its appearance and elasticity. The respect of this decisive step of the Marseillais process guarantees that the soap, once dried, remains hard and does not melt easily.