Probably the most commonly asked question in the world of soap making is "What is Trace?". One of the problems most beginning soap makers encounter is achieving trace properly. But what is trace anyway?
Trace is the so-called "point of no return" in soap making. It is the point where the oils or the fats in your soap have successfully mixed with your lye solution. More appropriately, this is the point where your oils and your lye turn into soap. The following are the tell-tale signs of trace:
- Your soap has a thick consistency similar to cake batter after you've mixed it.
- If after you drizzle some of the soap on the surface of the mixture, it leaves behind a "trail" that takes a while to sink back in the mixture.
Factors that Affect Trace
One major factor that affects the speed in which your soap achieves trace is the heaviness of the fat used. The heavier the fat or oil used, the faster trace occurs. For animals fats such as tallow or lard, you can expect to wait for about half an hour to one hour. For lighter fats or oils, such as vegetable oils, on the other hand, you can expect to wait several hours to even days before your soap reaches trace.
Another factor which affects the speed in which your soap mixture reaches trace is your method of mixing. With traditional hand mixing, it can take a very long time for your mixture to get to trace stage, but then again this also depends on many variables.
As I mentioned above, it can take a very long time for your mixture to achieve trace with regular hand mixing/stirring. Because of this a lot of soap makers have taken on more modern methods of mixing soap. Probably the most famous method is the so-called stick blender method. Using a stick blender, you can achieve trace within 5 minutes or less.
The best way to do it with a stick blender is to use one to two-second bursts, occasionally using the stick blender itself to manually stir. The following are suggested steps to take:
- Put your melted fats or oil in a big bowl. Slowly pour your lye solution into your oils.
- Use your stick blender to stir your oil and lye together until they're blended.
- Do one-second or two-second blasts/bursts with your stick blender. Do this 2-3 times.
- Use your stick blender to stir the mixture again.
- Repeat steps 3 and 4 until you see your mixture start to thicken up.
You can start testing for trace as soon as you see your soap start to exhibit a cake-batter-like or pudding-like consistency. To test for trace, use your stick blender to drizzle a bit of the mixture on to its surface. If you see a trail of soap which takes time to dissolve back into the mixture on the surface, you've achieved trace.
False trace usually happens when you use fats that are solid at room temperature such as tallow or lard. Your mixture, at room temperature will seem to thicken up faster than it should and you may be mislead to thinking that you've achieved trace. But it's not trace - it's your fats solidifying again. This is not good since if your soap will develop pockets of lye afterwards, which will cause danger to those who use it.
To prevent this from happening, make sure that as you mix your soap, the temperature of your mixture stays above the melting temperature of your fats. For instance, tallow melts at temperatures between 42 to 45 degrees Celsius but it stays liquid until its temperature falls to 33 to 34 degrees Celsius.
Why Check for Trace?
For one, trace will tell you that the fats and the lye in your mixture will have no more chances of separation. You wouldn't want your soap to have pockets of lye in it, right? But this is not the conclusion of the saponification. Rather only about 90% of the saponification process has been achieved at trace stage. Saponification is not completed until after you've cut your soap bars and left them out to cure.
After you've made sure your soap has achieved trace, you can now start incorporating additives like fragrances and colorants into your soap. You can also add additional oils or fats. This process is called superfatting. Superfatting makes for softer soaps and makes them produce more lather. A good rule of thumb to follow when adding extra oils is 1 ounce per pound of initial fat used in the mixture. It's common for soap makers to use exotic oils or butter when superfatting.
Superfatting is another way of making sure your soap does not have extra lye in it – especially if you think your weighing scale is not that precise. One needs to be careful when superfatting though since oil can spoil (see DOS or Dreaded Orange Spots). With more free fat or oil, it becomes more likely for your soap to develop pockets of oil which have gone bad. When designing your own recipe, you can either manually calculate the amount of fat or oils you can superfat in but most online lye calculators can do it for you. For some recipes instead of adding extra fat or oil you can "discount" the amount of lye you need to use in your soap. For example, if your recipe calls for 20 ounces of lye and you want a 2% discount, instead of using the whole 20 ounces use 19.6 ounces. Once you get enough experience you can try experimenting with higher or lower superfatting amounts yourself and see the results.