Updated: Feb 14, 2020
After ordering and waiting for supplies, taking the time to learn the fundamentals of soap science and the recipe formulating process, prepping your ingredients, and creating and designing your soap, comes one of the most fun and exciting aspects of the soap making process- “The Cut”. You have dedicated your time and energy into creating something unique and beautiful, and now you get to see your hard work in action. Unmolding and cutting a soap loaf is my absolute favorite part of the soap making process, right next to recipe formulating, of course! Unfortunately, there seems to be some confusion about exactly when and how to unmold and cut our soap, so, let’s take the time to explore this topic in more detail.
In our Facebook groups, we will often see comments such as, “I have been waiting for more than twelve hours and my soap loaf is still too soft to cut!” or a posted image of a soap with squished edges that says “I don’t know why my soap was still soft after I left it out overnight, did I ruin it?” I am not quite sure where this notion came from, but the idea that soap must be cut after just twelve hours or being left out on the counter overnight, is absolutely incorrect and it drives me bonkers.
The general rule regarding when to unmold and cut your soap is very simple- cut your soap when it is hard enough to do so without causing damage during the unmolding or cutting process. This hardening period may take an hour, it may take a day, or it may even take several days. Different factors will affect the rate at which your soap hardens and not all recipes will harden at the same. Some of these factors include fatty acid composition, water concentration, superfat, mold type, additives, soaping temperature, and more. A soap made from 100% coconut oil will harden at a much faster rate than a soap made with 100% olive oil. Why? Coconut oil is comprised primarily of saturated fatty acids, while olive oil is comprised primarily of unsaturated fatty acids. Coconut oil is solid at room temperature, while olive oil is liquid at room temperature. A soap that is made with a 1:1 water to lye solution will harden at a much faster rate than the same soap recipe made with a 3:1 water to lye solution. A soap made at 180F will harden at a much faster rate than the same soap recipe made at 80F. The chemical composition and methodology used during your soap making process will determine how much time your soap spends in the mold before it is hard enough and ready to cut.
A second factor to consider before cutting your soap is the prevention of soda ash. At trace, approximately 10-15% of the saponification process is complete. The rest of the reaction takes place in the mold. If there is a large percentage of the saponification process that remains prior to cutting your soap, you can risk personal harm and the development of a thick layer of soda ash. Soda ash forms when carbonic acid (water + carbon dioxide) reacts with sodium hydroxide to create sodium carbonate, also known by soap makers as "soda ash". By cutting your soap too soon, you not only risk handling soap that is too harsh for skin contact, but also risk the development of a thick, icing-like layer of pesky soda ash on the tops, sides, and bottoms of your soap. We recommend that students perform a simple zap-test prior to unmolding and cutting your soap in order to reduce these risks.
So let’s review, which two factors should you consider before cutting your soap? Your soap should be hard enough to cut without causing damage to your beautiful creation and it should be zap-free. If your soap is not hard enough to cut after twelve hours, contrary to what most beginners believe, that is absolutely OK! Your soap may need to stay in the mold for several hours, or it may need to remain in the mold for several days. If the soap is still too soft to cut, leaving it in the mold does NOT do any harm! I have several recipes that are made with higher water concentrations and lots of unsaturated fatty acids that must remain molded for up to three full days prior to cutting. I also have other recipes, such as my 100% coconut oil laundry soap, that must be cut within an hour or two, otherwise I risk attempting to cut a rock-hard loaf.
Although it may be very tempting to cut your soap early, you are stronger than you think and you can resist! No matter how excited you may be, by slowing down and cutting your soap at the right time, rather than rushing, you can ensure that you discover your beautiful soapy creation, without the risk of personal harm, damage to your soap, or the formation of dusty soda ash.
Questions or comments? Feel free to leave them below!