Making Soap – Part 2: Kitchen Chemistry in Action
Posted by notthatkat on August 24, 2007
When we left, we had a hot lye solution cooling on the counter. The next step is to prepare the oils. I use a mixture of coconut, palm and olive oil as my default base recipe, but I usually enrich it with other oils that are good for the skin. For this batch I am using both shea butter and hemp oil as enriching oils. The coconut and palm oil and the shea butter are solid at room temperature, and I tend to measure them first.
I buy coconut and palm oils by the five gallon bucket, although you may want to start with a smaller amount until you get a few batches under your belt.
All the oils are measured again by weight directly into the pan I will use to make the soap. When I do bigger batches where the total weight of oils and pan exceed the weight capacity of my scale, I measure the solid oils individually into a smaller bowl and dump them in the pot. I still measure my liquid oils in my pan so I don’t have to worry so much about how much I leave behind.
The next step is to heat the oils and melt the solid ones. This can be done on a kitchen stove, but I bought a portable burner a few years ago for demonstration purposes and use when making soap away from home which I find handy to have set up right in my work area. I use stainless steel pots and utensils since they do not react to the lye. Again, I can repurpose these for dyeing, but I do not use any of my soap making equipment for food.
I heat the oils until they are almost completely melted (the remaining pieces will melt soon enough), then remove from the heat. At this point the oils are at about 130 degrees Fahrenheit, while the lye has cooled down to about 145. What temperature to mix the two solutions together at is something of a matter of personal preference, and opinions vary widely as to the “ideal” temperature for soap making. I find that I can make very good cold process soap anywhere between 90 and 130 degrees Fahrenheit. I think it is more important to have your two solutions close in temperature, and I try to have them no more than 5 degrees apart within that range. The lye solution will cool faster than the oils, so I try not to get my oils too hot. This time I hit it about right, and I mixed when the oils measured 125 and the lye solution 127.
Now I mix the two solutions or “phases” by adding the lye solution to the oils in my soap pan. I lower the measuring cup very far into my pan and am careful not to splash the lye solution.
You probably know that oil and water don’t mix, and at this point there is a layer of oil (oil phase) floating on top of the dissolved lye solution (aqueous phase) The only contact between the two is the thin interface where they meet. Left alone, this would not become soap any time soon. I need to get better contact between my ingredients. You can stir by hand; that’s how I made my first few batches. A better (and easier) choice is to get an immersion blender (stick blender). You might be able to find one at a yard sale or thrift store, but they usually only run about 10 bucks at the local big box store, and I keep two on hand just for making soap.
As the two parts begin to combine, the mixture turns cloudy. I mix until it is a homogeneous opaque solution.
The mixture is mixed but still pretty thin. At this point, I change from constant mixing to pulse mixing, running the blender for about a minute followed by a minute rest so as not to burn out the motor. I am trying to get that elusive state known as trace. The mixture will thicken and if left to sit, the oil and water will not separate from one another.
This is the earliest stage of trace. The mixture is beginning to coat the blender, and drips remain visible on the surface for a second or two.
I’m not sure how well this shows up, but in the center, you can see the impression from where I removed the blender. It is about the consistency of instant pudding before you chill it and it sets up. You can mix to a thicker trace, but I only find that necessary if I am adding exfoliants (cornmeal, ground oats, etc) that tend to sink unless the mixture is very thick.
Now I’m ready to add my fragrance; for this batch, I’m using patchouli essential oil. I use both fragrance oils (synthetic) and essential oils (natural) depending on the effect I’m trying to achieve, but I prefer essential oils when feasible. I use fragrances for scents that have no natural equivalent (fruit scents except citrus, for example, cannot be found in natural form) and for ones that are insanely expensive (eg. rose, jasmine, sandalwood, vanilla). YMMV.
I measured my essential oil while I was waiting for my lye and oil to cool so it was ready and waiting for me. Once again I weigh my scents and typically use 0.7 oz of scent (total if I’m doing a blend) per pound of oil. I am making a 2.5 pound batch of soap, so I measured out ~1.75 oz of patchouli oil. Some people choose to scent by volume, and that is fine; just pick a method that works for you and be consistent. For stronger scents (mints and some spices) I scent less heavily – 0.4 to 0.5 oz per pound. For lighter scents (citrus) I scent more heavily – 0.9 oz per pound.
I add my scent now and mix it in well (my mixing picture came out very blurry). Most other additives are also added at this point, including exfoliants, most colorants, and dried herbs or citrus peel. Some essential oils (clove is notorious) and fragrance oils can speed up the reaction and cause the batch of soap to seize, turning from a thick liquid to a near solid very quickly or forming grainy particles. Others (more fragrances than essentials) can react to the lye and change, not always for the better. Often when I am trying out a new scent, I will make a 1 pound test batch to see how my scent or other additive reacts to the soap making process before committing to a large batch.
I pour the soap in the prepared mold and tap against the table to knock loose any bubbles and level it.
I cover the soap with plastic wrap and push it down against the surface. This prevents the formation of ash, which while not harmful, is not aesthetically pleasing. I try to smooth out any wrinkles, but I don’t get too obsessive about it.
I wrap the molded soap in a couple towels or a blanket and let it sit overnight. The chemical reaction that makes soap is an exothermic (heat generating) process, and we want to keep that heat in, as it drives the reaction faster. I let my soap incubate 18 to 24 hours at a minimum. At times I’ve left the soap in the mold for 2 to 3 days before I got around to messing with it again.
Here’s another natural breaking point, so here I’ll stop for another day.
Up next – the great unveiling, or is it done yet?