The earliest mention of this soap dates back to approximately the 700s AD.  It is made from olive oil, sweet bay laurel oil, water, and sodium hydroxide (aka lye, caustic soda) and was a widely sought trade item during the Crusades.

The ancient city of Aleppo was and still is famous for its production of some of the finest soap.  Aleppo is a city in Syria and has been producing soap for approximately 1300 years. Even now, the soap is made by hand using traditional methods.  Large blocks of soap are cut into smaller blocks and stamped with the maker’s mark.  These are then set out on racks to dry for six to nine months.  The process of drying hardens the outside of the bar and changes its color from olive green to a deep, rich gold. 

Aleppo soap is made from two fundamental ingredients: olive oil and laurel (bay leaf) oil.  The ratio of these two ingredients determines the properties as well as the quality of the soap. The higher the quantity of laurel oil, the better and the more expensive the soap.

Castile soap is simply a soap made from lye, water, and olive oil.  Aleppo soap is considered a Castile soap. London port books (1567–1568) record importations of "Castile soap" through Antwerp. John Hunt, in his article "A Short History of Soap," tells that barilla, an impure form of sodium carbonate from halophyte plant ashes, was boiled with locally available olive oil, rather than tallow.

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.(Hunt)

These soaps were known by their Latin names of sapo hispaniensis (Spanish soap) or of sapo castilliensis (Castilian soap).

The Crusades of the 11th century were the basis for the introduction of many things to the European market including soap and the process for making it based on the Aleppo soap.  This is not to say that soap was unknown in Europe prior to this, but rather the type, availability, and desirability for soap changed. The Laurel oil that made Aleppo soap so distinctive was not readily available to the European soap makers. The exclusion of the Laurel oil led to the formation one of the most popular - and still available - soaps ever, Castile soap.

A hand-milled soap is simply a soap that has been made from other soap and had scents or oils added to it. There is no exact date for when this process came to be, but there are recipes for hand-milled soaps in medieval household books.

There is a scented lye-based soap recipe in The treasurie of commodious conceits, & hidden secrets by John Partridge (Imprinted at London : By Richarde Iones, 1573).

 "To Make Muske Soape Take stronge lye made of chalk, and six pounde of stone chalk: iiii, pounde of Deere Suet, and put them in the lye; in an earthen potte, and mingle it well, and kepe it the space of forty daies, and mingle and [styr? fyr?] it, iii, or, iiii times a daye, tyll it be consumed, and that, that remayneth, vii, or, viii, dayes after, then you muste put a quarter of an ounce of Muske, and when you have done so, you must [sty?re] it, and it wyll smell of Musk."

A Delicate Washing Ball

“Take three ounces of Orace, halfe an ounce of Cypres, two ounces of Calamus Aromaticus, one ounce of Rose leaves, two ounces of Lavender flowers, beat all these together in a mortar, searcing [sifting] them through a fine searce [sieve], then scrape some castill sope, and dissolve it with some Rosewater, then incorporat all your powders therewith, by labouring of them well in a mortar."[1]

A Ball to Take Out Staines from Linnen

Take foure ounces of white hard Soape, beate it in a mortar with two small Lemmons sliced, and as much roche allome as an hasell Nut, roll it up in a ball, rub the staine therewith, and after fetch it out with warme water if need be.[1]

A Manly Soap Ball

This soap ball was inspired by the 14th century description from Boccaccio's Decameron: 

"Without permitting anyone else to lay a hand on him, the lady herself washed Salabaetto all over with soap scented with musk and cloves. . .

Rose Soap Ball

This soap ball was made using the following recipe: 5 Tbsp castile soap scrapings.

1 Tbsp Rose water 

1 Tbsp olive oil

3 dps Rose absolute (EO) to enhance fragrance if desired

This last recipe is a redacted recipe created after looking at several “beauty soap” recipes from period sources.  Rose water and lavender water were frequent ingredients in cosmetic-type preparations.