Castile soap

Early soapmakers in the Mediterranean area did not have easy access to laurel oil and therefore dropped it from their formulations, thereby creating an olive oil-based soap now known as Castile soap.

The sale of a monopoly in Protestant England to a Catholic company caused a great uproar, ending with the Castile soap company eventually being stripped of the monopoly.

In his article "A short history of soap", John Hunt maintains that barilla (an impure form of sodium carbonate obtained from halophyte plant ashes that were high in sodium) was boiled with locally available olive oil, rather than tallow.

[6] Adding brine to the boiled liquor made the soap float to the surface, where the soap-boiler could skim it off, leaving the excess lye and impurities to settle out.

While Aleppo soap tends to be green, this produced what was probably the first white hard soap, which hardened further as it aged, without losing its whiteness, forming jabón de Castilla.