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The basics of soap making
Ingredients: Oils, fats & Sodium hydroxide. A lot of people are horrified to see “Sodium Hydroxide” as an ingredient but soap can not be made without it. This is what happens in the reaction when you mix fatty acids (Oils & fats) & sodium hydroxide (Lye) -
Once saponification is complete you have glycerol (also called glycerin or glycerine), which is great for your skin, and the rest is the alkali salt of the fatty acid (soap) -
The lye is no longer present after the reaction has taken place, the lye and most of the fatty acids have neutralised each other, which is why is doesn’t appear on the ingredient label.
Each oil or fat needs a specific amount of lye for this reaction to take place effectively. 100g of coconut oil will need 18.32g of lye to fully saponify the fatty acids in coconut oil. Whereas 100g of olive oil will require 13.55g of lye for the same reaction. Measuring accurately is important for obvious reasons. Too much lye will leave the soap “lye heavy” and it would be rough on your skin. What soap makers do is reduce the lye by a specific amount to leave the soap with unsaponified oils or fats -
In “Cold process” soap making the ingredients are initially kept as cool as possible (although some don’t worry about the starting temperatures). Once the lye and oils are combined there is an exothermic reaction that’s going to take place regardless. Left to it’s own devices, and depending on the additives used, this reaction can get to temperatures of over 100oC. The increasing heat also burns off a lot of essential oils that might be used, which is annoying. The reacting mixture can be refrigerated to help keep the heat down but it takes 24 hours for the reaction to complete.
This doesn’t affect the quality of the soap but the cure time is longer, between 4 to 6 weeks. The cure time is merely the time needed for water to evaporate giving a harder bar that lasts longer.
Also, in cold process, the superfat can be any combination of the oils used -
The age old Hot process soap method goes a step further when combining lye and oils -
With either method you have beneficial free oils for moisturising but hot process means I can choose which it should be. Hot process takes a lot longer to make but the cure time is shorter as a lot of the water is cooked off.
I like both methods for different reasons; cold process soap batter stays a smooth liquid for longer, (though you still have to move pretty fast because it’s thickening all the time), and I can mess about with patterns and natural colours a lot more. I like hot process because of the ability to add specific ingredients that aren’t altered by the reactive lye and the cure time is shorter.
Cold process soap tends to have a smoother appearance than hot process soaps but I like the rustic handmade look as much as I like the design possibilities of cold processed soap. Either method gives a soap that’s really nice to use, full of natural glycerin and cleansing and moisturising.
In commercial soaps the glycerin content is often removed as it’s a profitable commodity -
|On the curing rack|