Posts Tagged ‘lye’

Blowing soap bubbles, a common pastime on washing day!

While flicking through the pages of my newly acquired Gentleman’s Magazine, Volume 31 (1761), I discovered a recipe for making soap!

Recipe to make Soap without boiling.

Set your leaches with hot water, put 20lb. of grease into a kettle with two pails full of strong lye, set it over the fire until the grease is well melted; then take a barrel placing it in the yard, or any other open place, where the sun may come to it, and fill it two thirds full of strong lye, and put the melted grease and lye into it, boiling hot, stirring it well together with a stick, and put in a pail full of weak lye every day, continuing the stirring of it until the barrel is full, and in about a week’s time you will have excellent soap.

[Editor’s postscript:] The above method has been tried in this town, Boston, New England, and found to exceed any common soap hitherto made by boiling, and will not be subject to any disagreeable smell by keeping; besides it will ease many worthy families from the confusion and vexation which usually attends the making of soap in the old way.

Soap is made when a fatty substance (plant oils, animal fat or “grease”) and an alkaline substance (such as lye) are combined and cause a chemical reaction, called saponification. Lye was historically obtained by running water through the ashes of burnt wood or plant matter and leaching out a solution of potassium hydroxide. The reaction that occurs when the fats and alkaline substance are mixed causes the surfactant qualities of soap, and heating helps to speed up the reaction.

The end result was a jelly-like substance, somewhat similar to liquid soap. It would be stored in a barrel and ladled out in the quantity needed. In order to get hard soap, common salt could be added to the mixture at the end, but this was not commonly done. Hard soap was not routinely made until the discovery of the process to make the alkaline sodium hydroxide, or caustic soda, by LeBlanc in 1790. Making soap with this alkaline caused the resulting mixture to go hard without the addition of salt.

Until the early 1800’s, soap making was largely a household chore, and was commonly held to be a difficult task. As eighteenth century pre-industrial people did not know about the chemical reaction that was occurring in their barrels of grease and lye, it was sometimes difficult to get a consistent result. One of the reasons for this was because it was difficult to know the strength of the lye (or alkaline solution). To much unreacted lye in the soap caused it to be caustic, but too little meant the soap was too greasy.

The Editor’s postscript, where he refers to the disagreeable smell of keeping soap, may refer to the smell of the rancid animal fat left over from cooking, which was saved for soap making. In addition, the process of cleaning the grease (rendering), by melting it in water and then letting it cool, was also not a pleasant smelling process!

I am not sure that soap-making is my cup of tea!

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Sources and Relevant Links

The Gentleman’s Magazine, Vol 31, 1761. Unfortunately I can not find an online version of this volume.

History of Soap Making

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