Curing and storing
Updated
Four to six weeks of doing nothing, in conditions that decide whether it works.
Airflow is the requirement
Water has to leave, and it leaves from the surface.
Bars need space around them: on edge or standing, not touching, not stacked, not in a closed box.
A stacked batch does not cure. It sits at the same weight for six weeks and the maker concludes the recipe is soft.
The rack
Open shelving with a mesh or slatted surface, or trays with air gaps.
Bars on edge take less space and cure more evenly than bars lying flat.
Label every rack with the batch number and the cut date. Six weeks is long enough to lose track, and a rack of unidentified soap is a rack of soap you cannot sell honestly.
Turning and weighing
Turn the bars once or twice over the cure so both faces dry evenly, which prevents the warping that shows as a curved bar.
Weigh three marked bars from each batch weekly. When the weight stops falling, the cure is done.
That is the measurement that replaces the calendar, and it is what makes the declared net weight defensible.
Where not to cure
Anywhere humid: a bathroom, a basement, a kitchen with something boiling. Soap will not lose water into air that is already wet.
Anywhere with strong smells, because cured soap picks up ambient odor.
In direct sunlight, which fades color and can accelerate rancidity.
And anywhere it will be disturbed, because six weeks is long enough for somebody to move it, stack it or put it in a box.