When it comes to whether you choose to insulate or not, really there are only two factors that will change. The first is the amount of cure time. Due to the fact that the saponification process is slowed down by the prevention of gel phase, your soap may need extra cure time before use. On the other hand, promoting a full gel phase for your soap means an accelerated saponification process with a normal cure time. And, the second difference is an aesthetic one.
The finished look of your soap will differ slightly based upon whether you choose to prevent gel phase or encourage it. By preventing gel phase (sticking your molded soap in the fridge or freezer), your finished soap will have a matte look to it. By promoting gel phase, your finished soap will have a slight translucent, shiny look to it. Again, however, please remember regardless of which method you choose either method results with finished soap.
When making soap, it is important to remember that the gel phase occurs during the saponification process. While your soap is in the mold, the various soaping ingredients react with the lye mixture, and heat is used to help the acceleration of the whole saponification process. When choosing to promote gel phase during saponification, it can be accomplished through means of insulation.
Insulating your soap means wrapping the soap with various layers in an attempt to keep the heat within the soap. Because the saponification process is endothermic (meaning the process pulls heat from its surroundings), keeping the soap insulated is the best means to successfully promoting gel phase throughout your whole soap. It will also help to prevent a partial gel. If you remember, a partial gel is where the center of your soap achieves gel phase, but the outside areas do not. This typically occurs because the outside of the soap looses heat in a quicker fashion therefore inhibiting the ideal environment for a full gel phase to occur.
Through the means of insulation, you can provide your soap with its ideal environment (heat wise). And, when it comes to insulation for your soap, there are many different items you can use. These items would include: newspaper, cardboard, blankets, towels, etc. Practically, you can use any layer type material that will keep the heat in the soap (but never aluminum foil).
Many soapers will use various items in combination such as: wrapping the soap with saran wrap (especially if the soap has a decorated top), then covering it with newspaper, surrounded by towels, and finally placed under a box. There really is no limit for insulation. And, many believe that over insulating can never be done. Remember the key to insulating, if you are choosing to promote the gel phase; is to keep as much heat in the soap as possible.
However, please note: If you are soaping a recipe that does contain sugar or dairy products, you may want to go a little on the lighter side of insulating due to the fact that these items in your recipe will increase heat during the saponification process. Extreme insulating in these examples may cause the ingredients to “burn”, possibly resulting in discoloration and an off smell in your finished soaps. It can also cause your soap batter to begin to bubble out of your mold. You do however have the choice of preventing the gel phase for these types of recipes, and sticking your molded soap in the fridge or freezer.