The importance of trace & its stages in soapmaking is often overlooked and not quite understood in crafting visually appealing handmade soaps.
I often hear my students tell me that the soap batter thickened so much before pouring into the mold OR that the batter remained so fluid that it took ages to harden up. All of these problems arise from not being able to judge trace properly.
Mixing the lye solution with oils begins the saponification reaction. Trace refers to the stage in which the oils and lye come together in a stable emulsion and will no longer separate. This is also called the point of no return. Because from this point on, the mixture will continue to thicken over time and will form soap even if left to stand on its own.
But if the soap batter were never to reach proper trace, it would separate back into its oil & water components! Oops!
Another importance of recognizing trace is to be able to create & execute design soaps successfully without messing up batches.
The stages of trace
Emulsion
This is the first stage of trace where the fats & the water components come together in a homogenous mixture. You cannot tell each other apart. This means that if you let the batter sit for a while, it wouldn't separate into oil & water. This is the point of no return and the only way to move is forward & 'thicker'. it appears like a thin coating of 'custard' on your stick blender.
Light Trace
When you blend further after the emulsion, you reach the ‘light trace’ stage. You know this stage has been reached when you dribble some soap batter on the surface with the blender or spatula and see thin lines ‘tracing’ the path you just made. The impression will most likely disappear before you even notice it. Visually, it can appear like 'thin salad dressing'
Medium Trace
This medium trace is the actual point that most soapmaking books or videos will tell you to stop at. The batter is considerable thicker at this point. Dribbling soap batter on the surface will reveal thick lines tracing the path that does not sink or disappear. It's neither too fluid or too thick.
This stage is when you pour the soap batter into the mold. You can also give the typical artisanal texture to your soaps when the batter is at this stage.
And this stage looks like 'ketchup' y'all!
Heavy Trace
Blending beyond medium trace leads you to a very thick 'pudding' like consistency, commonly called heavy trace. You can literally scoop up a dollop of soap with a spoon. It may be difficult to get an even texture when you try pouring the soap into the mold at this stage. But you can achieve gorgeous soap textures with this trace.
It can be difficult to judge these stages especially as a beginner. But if you are using well behaved, tested recipes, adequate water/liquid and a light touch on the stick blender, you will very clearly be able to recognize these stages and stay in control of your batter.