I tested it for you La Savonnerie de marin

Located in Marin, Savonnerie Marinel was conceived by Jean-Luc Le Toquin. Passionate about craftsmanship for over ten years, Jean-Luc has specialized in the manufacture of natural soaps, derived from reasonable, sustainable agriculture. From body and face soaps to hand soaps and shampoos, Savonnerie Marinel creates quality handmade solid soaps that are gentle on the skin and adapted to individual needs.

The workshop uses exclusively cold saponification.

“We use cold saponification. We say ‘cold’ because there’s no heat involved in soap-making. Well… which is a bit wrong, because when you pour caustic soda into water, exothermic heat is generated. It rises to 80-90 degrees. So you need to protect yourself with gloves and goggles when handling caustic soda.

We then wait for the solution to drop to 45 degrees. At this point, we heat the oils in a bain-marie to 40 degrees. The aim is for the two devices to be at the same temperature, plus or minus 40 degrees. Once you’ve done that, the hard part’s over. All that’s left is to blend the mixture with an immersion blender to a mayonnaise-like consistency. This means that the caustic soda, at the right temperature and in the right quantity, starts the chemical process that will transform the oil into soap and glycerine.

This is the beginning of saponification. The process takes around 24 hours. The mixture is placed in a wooden mold, where it first hardens, then generates heat, goes through a gel phase before hardening again to produce soap and glycerine. After 24 hours, 80% of the caustic soda has disappeared. The soap is left to cure for 4 to 6 weeks, so that no traces of caustic soda remain. After 6 weeks, the soap is ready for use.