All About ‘Gel phase’ in Cold Process Soap Making
Introduction
Watching a freshly made batch of handmade cold-processed soap go through its ‘gel phase’ is a glorious thing! I still think it’s magic :)
In this post I’ll go through everything you need to know about gelling cold process soap, including:
What it means to ‘gel’ soap
Why you should consider it in your soap making
What contributes to the speed and length of a gel phase
How to prevent or promote gelling of your soap
How to handle cracking and soap volcanos
In case you missed my video on this topic, including a nice view of my Eucalyptus Laundry Soap going through a full gel phase, you can view it here (or click on the video thumbnail image below).
For more information about this and other important soap making terms and concepts, please visit my Soap Making Terms page.
What does it mean to ‘gel’ soap?
Gelling soap refers to a stage in the saponification process where a soap batter heats up (saponification is an exothermic/heat-producing reaction), changes colour and appears to melt and become translucent (it looks like gel).
In cold process soap making, no additional heat is usually applied and the soap is allowed to naturally warm up, gel, then cool down, eventually hardening and returning to a lighter, opaque state.
In hot process soap making, the emulsified soap batter is treated with additional heat which forces it through and beyond the gel phase until the soap is ‘cooked’ and the saponification reaction is complete. (Hot process soap goes through a number of phases during the cook, including the ‘pudding’, ‘vaseline-gel’ and ‘mashed potato’ stages, depending on the recipe and methods used).
Why is gelling soap an important consideration for cold process soap makers?
There are good reasons for both gelling and not-gelling cold process soap, and it’s best to choose the method that is right for you, but there are a few important points to consider in your decision:
Ungelled soap can be lighter and creamier in appearance compared to gelled soap.
Milk soaps can transform to a dark caramel-brown colour when gelled due to the natural sugars present in animal milk or the cane sugar that is often added to plant-based milks. These sugars can scorch in the high temperatures generated during the gel phase. Many milk soap makers prefer to prevent gelling to maintain a light, creamy appearance in their soap.
Some fragrance oils and essential oils can accelerate saponification leading to overheating and discolouration in some soap recipes, especially if rapid saponifying oils are used in large amounts (eg. coconut oil, butters, waxes), or if the soap is made at higher temperatures. If your fragrance or essential oils are known to discolour, you may want to avoid gelling your soap to reduce this issue.
Many soap colourants, particularly natural colourants (such as indigo powders, alkanet root, madder root, turmeric) do not achieve their full vibrancy in ungelled soap. Some soap makers like the pale pastel look of ungelled natural colours in soap, some prefer vivid colours achieved through gelling.
Ungelled soap swells and absorbs more water in use compared to gelled soap.
Kevin Dunn, in his 2010 book Scientific Soapmaking, conducted experiments to test the effects of gelling or ‘melting’ on the qualities of handmade cold processed soap. These experiments found that ungelled soap swells more than gelled soap does when it is soaked in water. The book shows photographs of the difference in swelling between the gelled and ungelled soaps in this experiment, and while Dunn denies any great significance in this difference, I have personally found that my gelled soaps last longer and stay more firm when in use, compared to my ungelled soap bars. The firmness and longevity of your handmade soaps are determined by many factors (most prominently the oils used for the main soap recipe) however this factor is also worthy of consideration.
What contributes to the speed and length of a gel phase?
Some base oils used in soap making saponify more rapidly than others and can promote a hotter and faster gel phase. Saturated fats, butters and waxes are generally more prone to acceleration than soft/unsaturated fats and oils.
Sugars added to soap recipes also accelerate saponification and can promote a faster and hotter gel phase. Sugars include conventional ‘sweeteners’ such as cane sugar, honey and maple syrup, but it’s also important to consider the sugars present in other soap additives such as milks, fruit/vegetable purees, juices, and carbohydrates/sugars present in additives like ground oats and botanical ingredients such as aloe vera gel. These can all contribute to different speeds of saponification and gelling of your handmade soap batches.
Water amounts in handmade soap recipes are probably the most significant factor impacting the speed and length of gel phases. Low water soaps tend to gel much faster over a shorter period of time than do high water soaps, which can have very slow, extended gel phases. If you prefer very low water soap recipes (as I often do), and you would like to promote gelling of your soap, be sure to insulate your soaps well, use log or slab moulds, and/or add accelerating ingredients (sugars, etc.) to help promote a full gelling of your soap batches (more on this below).
How to prevent gelling if you are trying to avoid it.
The easiest way to avoid your soap gelling is to use individual silicone moulds or other small, non-insulating moulds. This way the soap will not retain heat and will stay as cool as possible throughout saponification, preventing heating and gelling of the soap.
Log and slab moulded soaps can be made with the coolest temperatures possible (depending on the minimum melting points of the base oils used) and then placed in the freezer as soon as they are poured and are firm enough to move. Depending on the recipe and the mould size this may be enough to prevent the soap from gelling, but there are no guarantees. You may encounter ‘partial gel’ with this method (where the soap gels in the centre but not all the way to the edges). Be prepared for some trial and error as you get to know what works with your recipes.
How to promote full gelling of your soap.
Soaps poured into log or slab moulds can hold heat the longest and are the easiest option if you want to ensure your soaps gel completely. Most of the time a basic wrapping with a towel or light blanket will be enough to keep the soap warm enough for a complete gel, however, if you are making soap in winter or your oils and/or lye are cool at the time of mixing, you may want to use a warmer or thicker wrapping (eg. multiple towels, wool or other warm blanket) to help maintain the heat through saponification.
If you would like to use smaller or individual bar sized moulds and would like to gel your soap fully, additional heat may be required. Sometimes quick wrapping with warm blankets or placing multiple trays of silicone moulds inside an insulating box can be enough to keep the soap warm, however if this set-up is not suitable or possible, an oven can also be used.
CPOP stands for ‘cold process oven process’ and is often used by cold process soap makers wanting to force the gelling of their soap through the use of extra heat provided by a warm oven. To ‘CPOP’ your soap, turn your oven on to the lowest heat setting (around 60°C/140°F is ideal) and carefully place the soap into the oven. Keep an eye on your soap and turn the oven off and leave the door ajar if you notice the soap has completely gelled. You can also heat your oven to a higher temperature, about 75°C/170°F and turn it off once the soap goes in. Try different methods and find what suits you best. Just note that each recipe will behave differently and there can be some issues with silicone moulds using the CPOP method. See my entries about ‘alien brains’ and ‘silicone rash’ on my Soap Making Terms page for more information.
What about cracking and volcanoes?
Depending on the recipe and soaping temperatures, there can be a risk of cracking on the top of your soap if it overheats through the saponification/gel phase process. If you notice your soap cracking, remove any insulation and allow it to cool at room temperature. You can often push cracks back together before the soap hardens with minimal cosmetic damage.
Soap volcanoes can occur when the soap overheats (through one or all of the accelerating factors listed above) and cannot be cooled in time to stop it from progressing through accelerated saponification stages, similar to a hot processed soap which puffs up and expands during the cooking process. If your soap volcanoes out of the mould, place it somewhere safe (put it on a tray to catch any overflowing soap) and once it settles it can be cut, grated and rebatched using this method.
Thank you so much for reading. I hope this has answered your questions about gelling handmade soap and given you some ideas to ponder for your future soap batches!
Please share this post and video with others who may be interested, and let me know if you have any questions or comments below :)
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