How was soap invented

The Arabs of the 7th and 8th centuries proved to be particularly skilled at making soap, right after the time when Mohammed founded Islam. With the spread of this religion, the art of soap making came to Europe via Spain.
The Arabs produce the first solid potash soaps by "causticizing" (= making them alkaline) of soda or potash with quicklime [calcium hydroxide].
In the early Middle Ages, centers of a flourishing soap boiler trade developed in the Mediterranean region.Soap boiler
Especially Spain, Italy and later France had the necessary raw materials. Olives served as a supplier of oil, and the ashes of seaweed contained soda.
In France, the soaps were refined by adding scents obtained from various plants. This was the birth of toilet soap, which was highly valued as cosmetic soap balls at Europe's courts, but was an inaccessible treasure for the majority of the population.
However, these soaps were not used for personal hygiene or for cleaning laundry or floors. They were used for cosmetic purposes or as medicinal products, and from 1525 for men's shaving.
Soap - especially curd soap - was an absolute luxury item that only well-to-do heads could afford.
Tallow and wood ash were still available in sufficient quantities in the 18th century. In addition, the desire to wash oneself and one's clothes regularly was not very strong.