How making hot process soap works
To make a soap one need only 3 ingredients: Water, lye and oil. It is that simple...
​
Yes, I know it does sound simple. It is as someone give you the recipe for bread: Water, yeast, flour and salt. What you do with it is important.
Lye and water are mixed together and then added to oils. Immediately process called saponification is starting. when lye water molecules are joining with oils molecules. For soap to be safe to use, all lye molecules have to be joined with oils, otherwise soap can sting and it can be dangerous to use. To calculate exact ratios of lye water and oils soap makers use special calculators where we plug in all oils and butters that we use in specific recipe and calculate amount of lye and water. We also use super fat percentage which is adding certain amount of oils or butters that will stay unsaponified. I use SoapCalc online calculator. On their web site there are many more information about quality of recipe, quality of fatty acids ( oils, butters, fats and different add ins like waxes, clays and more) and saturated and unsaturated fats ratios. These parameters help me know quality ad properties of soap recipe I developed.
When saponification starts soap maker can just pour soap batter into mold and leave it there to finish process by itself. It is called cold process soap making. If external heat source is added to speed up saponification it is called hot process soap making. That is process that I use.
When soap batter is mixed I place it in slow cooker and cook soap until the saponification is finished. That means that soap can be used as soon as it is cooled down. It can be used, but it is not the best that can be. Soap need to cure at least for 2 weeks for all extra moisture to evaporate, otherwise it can be short lived and quickly wear out in the shower. The more time soap is cured, longer it will last. Keeping soap outside of the shower and letting it dry between uses also prolong it's life.
My reason for choosing hot process (not considering nostalgia making it with my Granny) is very simple: it feels safer.
When I first started making soap I was very wary of lye. With small baby I wanted to be sure that his gentle skin is safe and protected. I felt it is a big plus that I can do ph test before I pour soap into the mold. Hot process is not as fluid as a cold process and in the beginning soap had rough edges and curved sides. Thanks to time, soap making books and experience, I found out a lot of ways to make the batter more fluid and easier to fill the mold. Soap makers in different forums have so much knowledge and ideas to add natural substances like yogurt or sugar syrup to the soap. With experimentation I managed to make hot process soap batter so fluid to do different molds, swirls and patterns.
Hot process was never more interesting and exciting.
​