Soap-making was a well-established craft in the Middle Ages, but what exactly went into medieval soap? A fourteenth-century English recipe provides remarkably detailed instructions, using ingredients ranging from sheep tallow and oak ashes to salt and wheat flour.
The recipe comes from The Trinity Encyclopedia, an anonymous fourteenth-century English manuscript containing a remarkable collection of practical craft recipes. Translated from Middle English by Mark Clarke, the text preserves instructions for manufacturing pigments, dyeing cloth, preparing skins and furs, imitating expensive imported leathers, counterfeiting semi-precious materials, making confectionery and carrying out many other useful tasks.
Among these instructions are several recipes for soap. One explains how to make white soap “in another manner,” providing unusually detailed directions for preparing the ingredients, cooking them together and determining when the soap is ready.
Soap-Making in the Middle Ages
Soap was certainly not a medieval invention. Versions made by combining fats or oils with alkaline substances had existed since antiquity. By the Middle Ages, soap-making had developed into a specialised craft in parts of Europe.
The ingredients could vary considerably depending on what was locally available. Mediterranean soap-makers had access to olive oil, while soap produced farther north could be made from animal fats. Wood ashes provided the alkali needed for the process. By the thirteenth century, soap-making was established in English towns including London, Bristol and Coventry, and soap had important uses in industries such as the preparation of wool and cloth.
The recipe in The Trinity Encyclopedia belongs to this wider tradition, but its level of detail makes it particularly interesting. Instead of simply telling the reader to combine fat and lye, it specifies quantities, waiting times and even how the mixture should behave when stirred.
What You Will Need
The medieval recipe calls for:
Ashes from an oak tree, used to prepare the lye
Sheep tallow, or rendered animal fat
Quicklime
White salt
Wheat flour
Water
A large pot
A brass pan
A sturdy stirring stick
A mould for the finished soap
Safety note: This medieval recipe involves highly alkaline lye, quicklime, boiling liquids and hot fat. These substances can cause serious burns and eye injuries. The instructions below reproduce and explain a historical recipe and should not be treated as a modern beginner’s soap-making guide. Anyone attempting historical soap-making should use appropriate protective equipment and modern safety procedures for handling caustic materials.
1. Preparing the Lye
The process begins with oak ashes. The recipe instructs the soap-maker to place “clean shifted ashes of oak” into a pot capable of holding three or four gallons and then add two gallons “scalding hot water to it.”
The mixture is stirred thoroughly, covered and left to stand for 24 hours. This creates the lye that will react with the animal fat. The recipe then calls for two ounces of quicklime and another two gallons of boiling water to be added. Everything is stirred again and allowed to stand for another day.
The use of wood ash was fundamental to traditional soap-making. Water passing through ashes produces an alkaline solution. Adding lime helped strengthen the alkaline mixture needed to react with the fat.
2. Adding the Sheep Tallow
Once the lye is ready, three quarts are placed in a brazen, or brass, pan and brought to a boil.
The recipe then states:
“And make it seethe, and then when it does, immediately take and add to it half a pound of nice clean tallow of a sheep that is completely melted beforehand.”
Tallow is rendered animal fat, and here the recipe specifically calls for sheep tallow. The melted fat is added to the boiling lye and the mixture is stirred continuously with a pot-stick or large stirring stick.
Half an ounce of white salt is then added and thoroughly mixed into the soap.
Next comes one of the more unexpected ingredients: wheat flour.
The recipe calls for a quarter of an ounce of flour, which is first mixed separately with a small amount of cold lye:
“Then take a quarter of an ounce of nice wheat flour and mix it with a little portion of your cold lye, and then draw it through a linen cloth into a dish in the manner of a starch.”
After being strained through the cloth, the flour mixture is added to the pan.
3. Knowing When the Soap Is Ready
One of the most useful aspects of the medieval recipe is that it doesn’t rely solely on measurements or cooking times. Instead, it tells the soap-maker to watch the consistency of the mixture.
The instructions explain:
“Continually be stirring in it until your material becomes so thick that you can see the base of your vessel during the stirring, and also such that it stands when you push it with your pot-stick without any running together again.”
In other words, the soap-maker should be able to draw the stirring stick through the thickened mixture and briefly expose the bottom of the pan. The mixture should also remain where it has been pushed rather than immediately flowing back into place.
The recipe anticipates possible problems as well. If the mixture begins to rise in the pan, it should be beaten down with a ladle.
More importantly, if the lye and tallow begin separating, additional lye should be added gradually, one quart at a time. The goal is to continue until the ingredients bind together:
“Until your materials hold themselves all well together in your pan without any separating or parting one from another.”
These instructions reveal the practical experience behind the recipe. Without modern thermometers, pH measurements or standardised ingredients, the soap-maker had to judge success by observing how the material behaved.
4. Moulding the Medieval Soap
Once the soap has reached the correct consistency, it can be taken off the fire. The mixture is poured into a mould that has first been moistened with water. The mould is then placed on a level surface and the soap is left to dry and harden.
The recipe finishes with a wonderfully straightforward instruction:
“Let it dry up in that same mould into a nice cake of soap as the manner is, and then it is done.”
For anyone wishing to produce more soap, the medieval author offers equally practical advice: use larger pots and pans and increase the quantities of the ingredients.
Would This Medieval Soap Actually Work?
Yes. The basic principle behind the recipe is the same chemistry used in traditional soap-making. Animal fats such as sheep tallow contain triglycerides. When these fats react with a sufficiently strong alkaline solution, they are transformed through saponification into fatty-acid salts, which are soap, along with glycerol. Wood ashes supplied medieval soap-makers with their source of alkali, while the tallow supplied the fat.
What is particularly revealing is how the medieval recipe compensates for the lack of standardised ingredients. Lye produced from wood ashes would not necessarily have the same strength from one batch to another. Instead of giving the soap-maker an exact chemical formula, the recipe repeatedly tells them what to look for: whether the ingredients separate, how thick the mixture becomes and how it behaves when pushed with the stirring stick.
The result is more than simply a recipe. It offers a glimpse of medieval practical knowledge in action, showing how craftspeople could control a complicated chemical process through careful observation and accumulated experience.
The recipe and many others can be found in Tricks of the Medieval Trades: A Collection of 14th Century English Craft Recipes, translated and edited by Mark Clarke and published by Archetype Books. You can buy it on Amazon.com | Amazon.ca | Amazon.co.uk
Top Image: The opening folio of Trinity College Cambridge, MS O.9.39, a collection of medieval English craft recipes that includes instructions for making soap. Photo courtesy the Master and Fellows of Trinity College, Cambridge.
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