The Gel Phase - "letting your soap gel"
What is the “gel phase”?
The gel phase is a part of the saponification process that happens after the soap has been poured into the mold. During this time soap gets hot, up to 180°F, and becomes more translucent in appearance. Though this is a part of the soap making process that can happen naturally, it is not completely necessary. Your decision on whether or not to let your soap gel depends on the result you’re looking for.
You will want to encourage the gel phase if you're looking for brighter, more vibrant colors in your soap. Gelling can make colors brighter or darker depending on the hue and adds a bit of a shine to the bars. This is especially true if using natural colorants, which can completely transform into the heat of the gel phase. The high temperature reached during the gel phase also makes the soap harden faster, allowing for easier unmolding.
To ensure that your soap goes through a complete gel, there are a few steps you can take. You can try increasing your soaping temperature to help kickstart the gel phase. Stay within the safe soaping temperature range, but on the higher side (around 125°F).
Another simple way to encourage the gel phase is to insulate your soap. Use cardboard, wood, or another safe material to cover your molds and wrap them up in a towel or blanket. This helps trap the heat naturally emitted during saponification. If you’re soaping in cold weather or a cooler room, you can also use external heat sources to ensure gel. Set your insulated molds on a heating pad set to medium for 30 minutes to an hour, checking to make sure it doesn’t overheat. You can also do a similar trick in a warm oven. Heat your oven to about 180°F and turn it off. Put your soap molds on an oven-safe tray or baking sheet and place them inside. Leave the molds in the warm oven for 6 to 8 hours.
You may want to avoid the gel phase if you are aiming for a more matte, muted bar of soap. Ungelled soap tends to have pastel colors and a creamier final look.
Some additives may have undesirable reactions during the gel phase. Milk, coffee, and other unconventional liquids can scorch during gel causing it to discolor and smell unpleasant. Additives with high sugar content, such as honey and fruits can have similar effects. It is best to avoid the gel phase when using these ingredients to maintain the look and content of the finished bar.
Avoiding the gel phase involves reducing heat rather than adding it. You can start by soaping at a lower temperature, around 90-100°F. After the soap is in the mold, place the mold on a wire cooling rack to allow air circulation which impedes heat retention. If you’re soaping in a warm environment or using ingredients that accelerate saponification you may need a little help keeping your soap cool. You can put the molds in the refrigerator or freezer for up to 24 hours to keep them nice and cold while they harden. Ungelled soap may need to stay in the mold longer to be hard enough to unmold and handle easily.