SOAP MANUFACTURING

Let's make... soap.
Soap has been made by hand since ancient times.
The reaction to obtain soap is called saponification.
It is as follows: oil + sodium hydroxide = soap + glycerin
Sodium hydroxide is commercially called caustic soda.
An oil is obtained by the esterification process, which consists of the reaction between an alcohol (glycerin) with a fatty acid (in our case, oleic acid, the one from the olive).
Esterification: fatty acid + glycerin = oil + water
Saponification is the reverse process: oil + caustic soda = glycerin + soap
The ingredients are: oil, soda and water.
Many ratios are suggested in books and on the internet. Most of them work. We have used the following: 600 g oil / 76 g soda / 177 g water
The oil can be new or recycled.
We use recycled oil and so it has to be filtered. It could also be strained, because filtration is very slow.
Weigh the oil.
Weigh the soda.
Weigh the water.
Prepare a solution of caustic soda.
Add the solution to the oil.
The reaction is slow and it is necessary to stir for half an hour.
As the minutes pass, it changes color, turning caramel. It also changes the viscosity: it becomes more viscous.
Pour the mixture into a container, such as those for milk, juice or chips.
Let the mixture rest for 24 hours.
If all goes well, it will have hardened and you'll be able to cut it.