There are two basic ways to make solid bar soap; hot process or cold process. The difference include using external heat, the time it takes to saponify, curing time and the finish of the soap.
External Heat and Saponification Time
Cold process soaps uses the exothermic heat reaction that is created from the acid and base reaction of the fatty acids (soap making oils ) and the lye solution.
When making cold process soaps you may have initially melted your solid oils down to a liquid form so that you can adequately mix the lye solution with the soap recipe fatty acids. No additional heat is used to actually facilitate the saponification process. Saponification takes about 18 to 24 hours to complete.
With hot process soap making an external heat source is used to accelerate saponification. The external heat source can be a crock pot, a double boiler or the oven. Saponification will be complete in approximately 2 hours.
Soaps made using the cold process method take about three to four weeks to cure. This of course depends on where you live. If you live in a region where the humidity is very low such as Colorado it could take your soaps one to two weeks to cure. If the soaps were made using the hot process method one week of cure time is sufficient.
Another difference between the two methods is how the soaps look. Cold process soaps have a more smooth finish to them. Whereas, hot process soaps have a more textured rustic finish to them. This is due to when the additives are added in both soaps. In hot process soaps, the additives are added at the end of the “cook” time. With cold process soaps the additives are added while the soap is still fluid giving the finished soap a more smother finish.
The choice to use one method over another is a personal choice. Neither method makes one soap method superior over the other.
Which method of soap making do you prefer? Please share you reasons below.