There are a few methods used to make make soap. For a completely customizable soap handmade from start to finish soap makers use either the hot process or cold process methods of making soap. For beginners or someone who wants to make small batches of soap quickly theres is also a products called melt and pour soap or milled soap sometimes referred to as rebatching which allows a person to take a pre-made soap base which is melted and customized with the addition of fragrance, colors and any additional add-ins. Each one has its pros and cons and which method and the methods used is based on personal preference.
Melt and Pour Soap:
Melt and Pour also referred to as glycerin soap starts with a soap base which can be clear or opaque. This is an option for anyone who wants to experiment with soap making with a big time investment. This method is pretty straightforward. The purchased soap base is cut or shredded and melted into a liquid form. Once the soap base is melted scents, colors or additives are incorporated, it can then be poured into a mold and left to cool. Although there are a few natural options on the market many of these bases still contain some undesirable additives.
Sample Ingredients for melt and pour bases:
Sorbitol, Propylene Glycol, Sodium Laureth Sulfate, Stearic Acid, Lauric Acid, Water, Sodium Hydroxide, Glycerin
Sorbitol, Coconut Oil, Propylene Glycol, Stearic Acid, Water, Sodium Hydroxide, Glycerin, Olive Oil, Aloe Vera, Yellow 5, Green 5.
Sorbitol, Propylene Glycol, Sodium Laureth Sulfate, Stearic Acid, Lauric Acid, Water, Sodium Hydroxide, Coconut Oil, Argan Oil, Shea Butter, Silk Amino Acids, Honey, Bamboo Extract, Sunflower Extract, Aloe Leaf Extract, Carrageenan Extract, Marshmallow Root Extract.
Plain shredded soaps made by hot or cold process are also available and may be melted and customized in a similar method as melt and pour. This is often referred to as milled soap or rebatching. One draw back of this method over melt and pour is that it doesn't always yield a smooth bar.
Hot Process & Cold Process Soap
Both hot process and cold process soap making begin in the same way. Warmed, melted oils fats and butters are combined with a warmed lye solution. The mixtures are stirred together until it reaches what is called trace. At this point, the two methods change. In the cold process, all of the scents, coloring, additional moisturizing oils are added to the soap batter at trace. It has not gone through the saponification process and the soap “batter” is still quite fluid, like the consistency of unset pudding. The soap is then poured into the soap molds and allowed to harden. After about 24 hours the soap can be cut and left to cure for 4-6 weeks.
There is some debate as to whether this curing time is necessary but the general consensus is to allow for a curing period. The more fluid batter of the cold process method allows for a smoother looking bar which can have different designs, colors, and swirls incorporated into it. The downside is the long curing time and the need to have all the additives in the soap before it goes through the saponification process, which can change or burn off a lot of the scent especially when using essential oils over fragrance oil for the scent
The hot process of soap making is my personal favorite and the one used at for Puro Co. soaps. The bringing process is the same as cold process soap but the oils and lye solution are combined in a heat safe dish to cook the soap through the saponification process. I used a crock pot when I first started making soap as it provides a low even heat for cooking soap. Once the soap reaches trace in this method it is covered and heated. The heat in this method speeds up the saponification process, so once it has finished cooking it is officially soap. At this point, the soap can be left to cool slightly, and desired add-ins are incorporated in. Once the soap is hardened it is ready to use, although allowing it to sit for a week or more will produce a harder bar as any excess water evaporates from the soap. I personally shoot for a minimum of 3 weeks+. In this method, the essential oils are added in at the end of the process so they don’t have to go through the heat of the saponification process. The soap at this point is much thicker, more like the consistency of applesauce so it produces a much more rustic looking bar. Hot process soap needs to be scooped into a mold where cold process is poured.
As you can see both the hot and cold process methods of soap making start out very similar, and the same base soap recipe can be used in both methods.
Want to learn more? Check out this post on Soap: A History and How it Works