This download is a pdf hyperdoc that has links to various cited sources for information on labeling soap. These sources are either government websites or from the Handcrafted Soap and Cosmetic Guild.
Note: In the US, children's soap requires lead testing. This information is cited in the hyperdoc from a government website.
In soaping forums I see many people looking for help controlling trace or trying to figure out why a batch went wrong. Well-meaning people often suggest that they need to soap while their oils and lye are within 10°F (5°C) of each other. Let me talk about why this answer bothers me.
I frequently make soap with my lye solution around 75°F and oils around 95°F. I am able to create intricate swirls like this. However, if I soap with my lye solution at 150° F and oils at 160°F, I can expect for my soap to move along much more quickly even though they are within 10°F of each other. Then there’s the heat transfer method where you use the hot lye solution to melt your hard oils and butters. Those are just three counterexamples (when you really only need one) for the suggestion to soap with oil and lye between 5-10 degrees of each other. Why do people still push this concept?
I do see reputable soapers mention that the oils and lye should be within a specific range of each other AND mention that they should keep them at a certain temperature. Soap Queen recommends soaping between 120°F and 130°F (https://www.soapqueen.com/bath-and-body-tutorials/tips-and-tricks/back-to-basics-how-temperature-affects-cold-process-soap/). This blog states that books and soapers recommend oils and lye be within 10°F of one another, but I didn’t see an explanation of why. I have not seen evidence that they need to be within a certain range of each other. Modern Soap Making suggests keeping your temperatures below 110°F to help control trace and keep your soap batter behaving nicely. They even mention that your oil and lye do not need to be within 10°F of each other. Here’s a link to their really great blog on the topic: https://www.modernsoapmaking.com/blog/controlling-trace-in-cold-process-soapmaking
Why in the world do so many people suggest the oils and lye be within 5°-10° of each other? Why are we not explaining more frequently a certain range for soaping overall instead of how close in temperature the oil and lye need to be? I know it would be confusing and frustrating to a new soap maker to have their oils and lye within a certain range of each other only to experience acceleration, because they were 145°F and 140°F, which is quite warm. I don’t see where it can be a safety concern, but it does seem like an outdated concept, and it’s frustrating to see misinformation on the topic. Your lye and oils do NOT need to be within a 5°-10° range of each other, but it would be best to stay at a cooler temperature if you want to keep your batter fluid. I tend to soap with room temperature lye, around 75°F, and oils around 90°F-100°F. As you can see, I am able to make some good soap like this. We will all have our own sweet spot as to what temperature works best for us and our recipes, but it probably isn’t going to be based on how close in temperature the oils and lye are.
As always, safety first, and then have fun.
When I say, “Castile,” I’m referring to 100% olive oil soap, not any vegetable-based soap. 100% olive oil Castile soap is made of olive oil, water, lye, and whatever additives the soaper chooses (oatmeal, clay, scents, etc.) This soap tends to be in a league of its own. It’s not my favorite for hand washing, because it doesn’t dry out as well between uses since I wash my hands much more frequently than I shower. It really needs to dry well between uses to be its best. I recommend using it for face or body washing 1-2 times per day. You could also rotate bars of castile soap for handwashing so the bar doesn’t get used more than a couple of times per day and can dry well between uses. Use a well-draining soap dish or soap lift, let it air dry well between uses, and you will probably love your Castile soap and increase its longevity drastically. These tips could be applied to other 100% oil soaps as well.
Blended Oil Soaps
Many handmade soaps are a blend of various oils, fats, and butters. I’ve found my blended oil soaps are much less finicky to work with. They still need to be kept in a well-draining soap dish or soap lift, and they still work better when they can dry between uses. I keep one in the bathroom at work where many people use my soap. It does not get to dry between uses, and it performs well and lasts a good while. I keep it on a soap lift, or soap saver pad, and it does pretty well. My favorite thing to do is cut a bar of my soap into halves or thirds and leave one piece by the sink at a time. The smaller bars seem to dry a bit better between uses, and I can rotate pieces if I feel like the soap needs a break to dry a bit. I don’t usually rotate pieces, but it’s an option that I think some would prefer.
Main takeaway: Don’t let your soap sit in liquid. It will get slimy, and it will decrease its longevity. Let it dry as much as possible between uses, and it will be living its best life while you enjoy your wonderful handmade soap.
One of the most frustrating things to see answered in soap forums is the question, “Why did my cold process soap crack?” Even well-known soapers tend to say that cold process soap cracks, because the soap got too hot. Heat is the cause, but it’s not necessarily a sign of too much heat. It can often be a sign of inconsistent heat. Usually you see this when the top of the soap is too cool to expand with the internal heat during gel phase, and it cracks. Many times, insulating your soap will actually prevent cracks from happening.
Clara Lindberg has written a wonderful blog on the topic of what’s hot when it comes to making soap (https://auntieclaras.com/2015/06/overheating-soap/). One of the many things she mentions is water content. I’ve never found any reason to use the standard 38% water as a percent of oils. I actually don’t love using water as a percent of oils. Instead I prefer liquid:lye ratio and lye concentration, but that’s a different topic for another time. 38% water as a percent of oils is way more water than I can rationalize ever needing in cold process soap. More water means a hotter soap. When you control the amount of liquid, or water, you use in your recipe, you’ll have a much easier time controlling the outcome of your soap.
I tend to keep my water content just under a 2:1 water:lye ratio. Then I use my oven to ensure an even and full gel phase, and I even oven process milk soaps. I preheat my oven to 170F, turn the oven off, turn the oven light on, and leave the soap in the oven, uncovered, overnight. When I began soaping this way, my soaps stopped cracking. I honestly thought it was a far-fetched idea to insulate my soap when so many people kept saying the cracking was from overheating, but lo and behold, adding or retaining some of the heat prevents cracking. Teri from Tree Marie Soapworks mentioned that, "Cold soap cracks. Warm soap expands," referencing Clara's blog, and I'm glad I took the advice of these skilled soap makers.
The soap cracks when the top cools quickly and can’t move with the warm soap which is expanding in the middle. The cooler top cracks against the internal heat. If you’re making 100% coconut oil soap, have a high water content, or include additives that make the soap hotter (sugars for example), then it's possible the soap is cracking and may be about to volcano. I've only seen anything close to a volcano once, and it was with a 100% coconut oil dish soap I was making. If your water content is not too high, then it's most likely fine, but exercise caution and keep an eye on your soap until you have built your confidence with this and know what to expect.
What happens when you use the standard water in a soap calculator and add heat through insulation or oven processing? Loads of things can happen, and most are less than desirable. If you want to force glycerin rivers for a design choice, then this might be the way to go. However, the results often may not be what you love. Refer back to Auntie Clara’s blog I linked earlier. I’m not reinventing the wheel by doing my own experiments and documenting them for this blog post when Clara has such a beautifully written blog already. Plus I’ve already seen many of the things mentioned in her blog, and I don’t really want to do them again just for the sake of documenting them.
To summarize, I think it is rarely necessary to go above a 2:1 liquid:lye ratio when making cold process soap. I wish someone had told me that sooner when I was a new soap maker. I can’t even figure out why we tell new soap makers to use the full water amount (Soap Calc standard 38% water as percent of oils) until they get used to making soap. The full water amount is what causes so many problems anyway. To keep your soaps from cracking, remove the wild card of excess water, and insulate your soap. Keep a close eye on it until you know how your recipe will behave, and have a safety plan in place in the event something does go awry. For example, maybe place your mold in a large soap-safe container to catch potential volcanoes. Honestly, I think it’s good advice to have a safety plan in place regardless of your water content while you’re learning how to make soap or when trying something new.
Soap making involves a great deal of trial and error and making adjustments until you find your sweet spot with how you are happy and comfortable making soap. Your main focus is to following safe soap making practices, and then enjoy the learning process.