The gel phase of soap making is the heating stage of saponification. Once you pour your soap into its mold it will start to heat up. Gel phase starts with the soap turning translucent in the middle and then spreads out to the edges.
Check out this goat’s milk soap that is just starting gel phase.
More gel phase.
If your mold is not insulated or not able to hold heat then your soap might not gel. No worries, soap does not have to gel in order to turn out properly.
The biggest difference between gelled and un-gelled soap is the color of it. Colors can sometimes appear darker in gelled soap. Check out this soap. The darker color went through gel phase in a log mold and the lighter round soap (from same batch) did not go through gel phase. What a different in color!
Un-gelled soap can also take longer to harden enough to remove it from the mold.
Please note that some fragrances, especially floral type scents, honey and other additives, can heat your soap up. It can sometimes be impossible to prevent gel. Many soap makers choose to try and prevent gel when soaping with milk, as milk soap heats up and can overheat causing cracks and other issues.
Below is a lavender soap that I just poured into the mold. Below it is the same soap going through gel phase. Gel phase is really dark in some soaps, but in this one, it wasn’t that dark, but you can see the difference in translucency.]
The soap below is going through gel phase and is getting so hot that it is cracking. Soap cracks when it is trying to release the high heat inside.
If you see your soap cracking, try to cool it down. You can put it in the fridge or freezer, or you can simply elevate it onto a cookie rack (or something similar) and shoot a fan at it. If it is cold where you live, simply put it outside.
Sometimes it can be alarming to see your soap going through gel phase. Now you know what is going on.
Partial Gel in Soap
Soap can partially go through gel phase. You’ll know that this happened when you cut your soap and there is a dark circle in the center. This is simply an aesthetics issue; your soap is perfectly find to use. Here are some examples of partial gel.
Take a close look at my Frankenstein soap. The partial gel is very light, but you can see the darker center.
And another soap, my candy corn soap, has a partial gel. Check out how it affects the colors! The good news is that after a bit of time, the colors evened out.
To prevent a partial gel in soap, you can prevent your soap from gelling or force it all the way through the process. See below.
Preventing Gel Phase in Soap Making
Sometimes soap makers want to prevent their soap from going through gel phase. I know many soapers who prevent their milk soaps from gelling because they want them to look nice and light in color. Here are some things you can try to prevent gel.
- Discount your water. To understand why, check out Kevin Dunn’s book, Scientific Soapmaking. Use a water discount to prevent gel. I personally use water at two times my lye and my soap hardly goes through gel phase unless I force it using some techniques below.
- Make smaller batches. If there is a smaller mass of soap, it can’t hold heat in as well. Slab molds are great for preventing gel because the soap mass is spread out with lots of surface area for heat to leave.
- Put your soap in the fridge or freezer. I know many soapmakers who make a loaf of soap and stick right into the fridge or freezer.
- Elevate your soap after you pour it. Use a cookie rack or something similar to provide airflow around your mold. You can even aim a fan at it to keep it cool.
- When your pouring multiple loafs, don’t line them up together touching. Let plenty of air circulate around each mold.
- Soap at cooler temperatures. Aim for temps of 80-90 degrees F for both your lye solution and oils.
Forcing Gel Phase in Soap Making
There are many times in soap making that you will actually want to force your soap through gel phase. It might be because you are tired of partial gel, or it might be that you are soaping with natural colorants so you want to force gel to get vibrant colors.
Here are some tips for forcing gel phase.
- Soap warmer. Make your soap with your oils and lye at warmer temps. If you currently soap at room temp or 80-90 degree F, try soaping at 100-110 degree F. Now remember, higher temps can make your soap speed up! So if you are trying to swirl and do more intricate designs, then try another technique below.
- Use more water. It can be hard to gel soap with a water discount. To understand why, check out Kevin Dunn’s book, Scientific Soapmaking. Use more water to help force gel.
- Cover your soap with wood or a cardboard box to hold the heat in.
- Set your soap on a heating pad to force gel. Combine this with covering your soap with wood or a cardboard box and you’ll be creating heat and making sure that it stays in the soap.
- Use your oven to force gel. Many soapmakers use a process called cold processes oven process (CPOP) to force their soap to gel in the oven. I’ve used it quite a lot. Here is how I do it.
- I turn my oven on to warm (your want it to be about 170-180 degrees F.
- I made my soap as usual.
- I turn my oven off and put my soap inside the warm oven and leave it over night.
Some soapmakers leave their oven on warm. If you do that, just keep a close eye on your soap. Once you see it complete gel phase you can remove it and let it cool down.
Keep an eye on your soap if you CPOP. If you’re soaping with spices, florals, sugars (including honey), milk and alcohol, all of these additives can help to heat up your soap. You don’t want your soap getting to hot in the oven and then cracking or volcano-ing out of the mold.
To gel or not to gel is simply a matter of preference! Don’t be afraid to experiment!