So.
Also, die Haarseife hat einen pH-Wert von 9, was mich vermuten lässt, dass es wirklich Seife ist.
Die Seifensorte scheint eine Seife auf Pflanzen-Soda-Aschen-Basis zu sein - was schon very, very, very old school wäre. ;)
Wikipedia sagt dazu (nur englisch, sorry..): (Artikel über "Natron" und "Soda_ash")
Several "halophyte" (salt tolerant) plant species and seaweed species can be processed to yield an impure form of sodium carbonate, and these sources predominated in Europe and elsewhere until the early 19th Century. The land plants (typically glassworts or saltworts) or the seaweed (typically Fucus species) were harvested, dried, and burned. The ashes were then "lixiviated" (washed with water) to form an alkali solution. This solution was boiled dry to create the final product, which was termed "soda ash;" this very old name refers to the archetypal plant source for soda ash, which was the small annual shrub Salsola soda ("barilla plant").
The sodium carbonate concentration in soda ash varied very widely, from 2-3% for the seaweed-derived form ("kelp"), to 30% for the best barilla produced from saltwort plants in Spain. Plant and seaweed sources for soda ash, and also for the related alkali "potash," became increasingly inadequate by the end of the 18th Century, and the search for commercially-viable routes to synthesizing soda ash from salt and other chemicals intensified.[10]Historical natron was harvested directly as a salt mixture from dry lake beds in ancient Egypt and has been used for thousands of years as a cleaning product for both the home and body. Blended with oil, it was an early form of soap. It softens water whilst removing oil, grease, and alcohol stains. Undiluted, natron was a cleanser for the teeth and an early mouthwash. The mineral was mixed into early antiseptics for wounds and minor cuts. Natron can be used to dry and preserve fish and meat. It was also an ancient household insecticide.
Das ist, was ich in etwa wusste - man verbrennt Seetang und gewinnt daraus Sodaasche, die als Pottasche zum Seife machen verwendet wird.
Na, da bin ich ja super gespannt. :)