THL Elska á Fjárfelli has put together some WONDERFUL research on period soapmaking. Read her entire blog post here. Below I’ve pasted some of the basic information from her blog post that pertains to pre 17th-century Italian Peninsula.
What is Soap?
First things first. To undertake soap making one should be familiar with what soap is and why it works the way it does. In short, soap is a simple molecule with the unusual ability to dissolve fats and oils into water, making it possible to rinse them away. It is made by mixing dissolved hydroxide salts with fatty acids, resulting in fat salts or soap (for instance, tallow mixed with sodium hydroxide becomes sodium tallowate, or tallow soap). This process is called saponification, from the Latin word sapo for soap. And if you are an outdoor enthusiast you might have inadvertently made soap already. Scrubbing a greasy frying pan with campfire ashes does not just scour the dirt away; rinse with a little water and the hydroxide salts in the ashes will combine with the cooking grease into a primitive cleanser – a way of cleaning dishes and laundry that has been with us through Ancient times!
Soft Soap VS Hard Soap
Black soap, or soft soap, gets its name from the dark color of the wood ash lye used to make it (and the cast iron it was often boiled in). Hard soap was made with high quality barilla ashes, which makes a light colored lye (and hard soda soap); therefore white soap quickly equated with high quality hard soap. Why is this important? It’s because sodium hydroxide made from marine and marsh plants makes solid bar soaps, while potassium hydroxide from land based plants makes liquid or soft soaps. Sodium hydroxide is a small molecule with short and tight molecular bonds which creates soap with a strong crystalline structure. Potassium hydroxide is a large molecule, with long weaker molecular bonds, which creates soap with a weak crystalline structure. It’s the lye that makes the soap.
Soap Through The Ages
The first mention of soap being used on a human body for cleaning was in the 4th C: French soap was described by Theodorus Priscianus as a material for washing the head. (Dunn, 233) By the 7th C Italian soap makers were organized into craft guilds and the profession of soap maker is mentioned in Charlemagne’s Capitulare de Villis of 805 AD. By the 8th C, soft soap made with oils was common in France, Italy, and Spain, as olive oil was widely available. It is generally accepted that soap was known in England by the 10th C, most likely introduced by the Celts. (Bramson, 57) Another early reference to soap manufacture is by the monk Richard of Devizes in about 1200CE: “Apud Bristollum nemo est qui non sit vel fuerit saponarius” (about the number of soap makers in Bristol and the smelly nature of their profession). (Matthews, 4) Also by the 12th C, hard soap came into use which was said to be an Arab development later imported into Europe. By the 13th C, the manufacturing of soap in the Islamic world became virtually industrialized, with sources in Nablus, Fes, Damascus, and Aleppo. Around the 13th C, Marseilles emerged as the first great center of European soap making and remained so throughout the Middle Ages. (Bramson, 59) Genoa, Venice, and Bari in Italy and Castile in Spain also became epicenters of soap making due to their natural resources. (Bramson, 57) All had abundant supplies of olive oil and barilla, (Bramson, 57) a sodium rich plant whose ashes were used to make soda lye, a perfect combination to make a beautiful hard white bar of soap.
Since hard soap can be shredded and reformed soap balls came into being, a luxury product used by the upper classes. In Tudor times botanicals were introduced into soap, and scented soap became a “must-have” item of the elite. Fine soaps were produced in Europe from the 16th century on, and many of these soaps are still produced, both industrially and by small-scale artisans. Castile soap is a popular example of the vegetable-only soaps evolved from the oldest “white soap” of Italy. This hard white soap would be grated and used to make specially scented and herbed soap balls/ wash balls.
Couture Wash Balls
Making soap balls is easy, as all one needs to do is grate soap into slivers (by hand or with a kitchen machine), add a tiny bit of water or milk to make the slivers sticky, kneed a bit by hand and then roll the sticky mass into a ball. Dry for a few days and the soap is ready to be used. Plain olive oil based soap like Castile Soap most similar to medieval white soap. Here is a recipe for a musk wash ball.
White musked soap – Take soap scraped or grated, as much as you need the which (when you have well steeped and tempered in rose water) leave it eight days in the sun: Then you shall add to it an ounce of the water or milk of Macaleb [Prumus maheleb], twelve grains of musk, and six grains of civet, and reduce all together into the form and manner of a hard paste, you shall make of this very excellent balls. (The secretes of the reuerende Maister Alexis of Piemount (1558) by Girolamo Ruscelli)
Historical Soap Recipes
From the Mappae Clavicula comes the following soap recipe using wood ash lye. This recipe uses the word “clarified” in connection with evaporated lye, which I interpret to mean the lye was decanted off its sediments. Especially in older recipes from Guild sources information can be presented incomplete or out of order, in this case mentioning heat after clarification, but since later period recipes confirm the process this interpretation makes the most sense.
280. How soap is made from olive oil or tallow
Spread well burnt ashes from good logs over woven wickerwork made of withies, or on a thin-meshed strong sieve, and gently pour hot water on them so that it goes through drop by drop. Collect the lye in a clean pot underneath and strain it two or three times through the same ashes, so that the lye becomes strong and colored. This is the first lye of the soapmaker. After it has clarified well let it cook, and when it has boiled for a long time and has begun to thicken, add enough oil and stir very well. Now, if you want to make the lye with lime, put a little good lime in it, but if you want it to be without lime, let the above-mentioned lye boil by itself until it is cooked down and reduced to thickness. Afterwards, allow to cool in a suitable place whatever has remained there of the lye or the watery stuff. This clarification is called the second lye of the soapmaker. Afterwards, work [the soap] with a little spade for 2, 3 or 4 days, so that it coagulates well and is de-watered, and lay it aside for use. If you want to make [your soap] out of tallow the process will be the same, though instead of oil put in well-beaten beef tallow and add a little wheat flour according to your judgment, and let them cook to thickness, as was said above. (Mappae Clavicula; A Little Key to the World of Medieval Techniques, 12th C.)
The following recipe from the Secretes of Alexis of Piemont mentions the correct proportions of lye to oil for a successful soap boil “vnto three pound of the saide lie, you muste haue one pound of oile” and also stresses not to boil but to simmer the soap; for a long, long time.
To make black Sope for clothes, with all the signes and tokens that it giueth and maketh in beiling.
[…]Use 3 pounds of egg bearing lye to 1 pound of oil, pour the oil in and stir and mix well. Do this in the evening so that the infusion can stand overnight. In the morning start to simmer it, for seven to eight hours; if it is over 100 pounds simmer ten hours or more. When it starts to simmer and rise up a lot, take it from the fire and stir it well until it starts to go down again. Keep stirring so it does not get burned to the bottom. When you use a cauldron leave a hand width of space because the soap rises and swells in cooking and oil would be lost. The more it is stirred and the oils incorporate well with the lye, the sooner it simmers. When it has simmered for about eight or nine hours it is time to take samples and check. Make sure to have some first and second lye ready as needed. When it has boiled until the right time you shall see it become thick, and make long and thick bubbles when simmering. To take a sample, take a little with a spoon and put it on a small earthenware dish and let it cool. Then cut it with a little stick and if it closes again it is a sign it has cooked enough; if it does not close, it is not finished, so keep simmering it [this is reversed]. Take many samples and check. [..]
(The seconde part of the Secretes of Master Alexis of Piemont by Girolamo Ruscelli, 1560.)
The Secret To Hard Soap
Liquid soap worked well for cleaning and laundry but dilutes quickly and thus wastes more than hard soap; hard soap was prized for its economy but because of the lower availability of sodium hydroxide much more expensive. Historically, sodium lye was made by leaching sodium rich ashes, made from burning marine or marsh plants. Coastal regions with access to these plants, especially Barilla which is known for sequestering sodium chloride in unusual high amount, had access to sodium rich lye and could therefore make hard white soaps. For instance Savon de Marseille and Aleppo soap are well known modern soaps based on century old techniques, with Nabulsi soap tracing its roots all the way to the 10th century.
As the coastal plant barilla is hard to come by, making historic white soap is challenging. One way around this is to burn kelp to ashes, which is available in 50# bags at your local feed store. Kelp is a marine plant and produces sodium lye, but as it does not sequester salt the way barilla does, a lot more kelp is needed compared to barilla.
Strength of Lye
The following recipe from the Secretes of Alexis of Piemont (1560) mentions the correct strength of lye used to make laundry soap: “…put the Egge into it, and whiles the egge remaineth aboue…” or a floating egg.
To make black Sope for clothes, with all the signes and tokens that it giueth and maketh in beiling. […] To know the difference between first, second and third lye, take a fresh egg wound around with a thread [to be able to take it back out] and as the first lye comes out float the egg on it. Save this lye for as long as it floats as this is the best lye. […] (From The seconde part of the Secretes of Master Alexis of Piemont by Girolamo Ruscelli, 1560.)
The following medieval cold process recipe on how to make a shampoo, uses a different strength of lye which I found from personal experimentation to be neutral. It mentions “… that will beare an egge swimminge be|twene two waters…” or, the egg is not floating on top, but suspended in the middle. Suspended-egg lye makes near-neutral soap that does not ‘bite’, which makes complete sense as this is a soap meant for personal use. This recipe also confirms the amounts of “thre pottels of lye to a pot of common oyl”; the 3:1 ratio which consistently works well for me.
More From the Original Blogger
Her blog is “A most copious and exact compendium of mediaeval secretes collected by THL Elska á Fjárfelli.”
Read her full post on modern and medieval soap, plus her bibliography here http://bookeofsecretes.blogspot.com/2016/09/modern-medieval-soap-making-compared.html?m=1
Several of her soap making research papers and class hand-outs are available from Academia at https://independent.academia.edu/susanverberg