Make soap from scratch using this simple and moisturizing hot process soap recipe. The recipe includes skin-loving mango butter and yogurt and includes a DIY video along with full hot-process soapmaking instructions
One of the best things about hot process soap is that you can make it and have the soap ready to use almost right away. That’s because cooking the ingredients speeds up the soap making process and means that the end product is gentle on your skin from the moment it finishes cooking.
This is a straightforward hot process soap recipe that will give you between eight and ten good-sized bars. It includes just four relatively common soap making oils, including coconut oil, olive oil, castor oil, and lush mango butter. You’ll also melt half of the mango butter and add it after trace as a superfatting oil. This step makes all the difference in how the soap feels when you use it—a creamy yet well-lathering bar of soap perfect for hands, body, and even face.
Cold-process vs. Hot-process
The vast majority of the soap recipes that I share include instructions using the cold-process method. I’ve even recently released a comprehensive Guide to Natural Soapmaking that focuses on making soap from scratch in that way. In many ways, hot-process can be very similar to cold-process in that you combine oils and a lye solution and help them saponify – in other words, to become soap.
The main difference between cold-process and hot has to do with temperature. You cook hot process soap to speed up the full process of saponification so that, in the end, the soap is technically ready to use right away. Typically, you use a slow cooker (a crockpot) for cooking hot-process soap, but you can also do it in the oven or on the stove-top.
In standard cold-process soapmaking, saponification is mainly complete in the first 48 hours, but it can take up to a month to finish. The exception being handmade dish soap, which you can technically use after two days. However, if you use cold-process body soap before the cure time is up, then it can feel harsh on your skin, or not have the bubbles and lather that it could have if you wait for the 28-cure time to complete.
Simple Hot Process Soap Recipe
I’ve created this simple hot process soap recipe for beginners, including experienced cold-process soap makers. Many people who have been making cold-process for years feel a bit daunted by the idea of cooking soap in a slow cooker. The instructions and explanations I provide will make the transition more comfortable and help to answer your questions.
One of my biggest questions when I was first researching how to make hot-process was which recipes to use. It isn’t immediately obvious, but you can make practically any from-scratch soap recipe in either the cold-process or hot-process method. The benefit of the cold-process is more control over colors and final texture while making soap with the hot process method is quicker. You also don’t have to deal with issues like soda ash forming on your bars in hot-process.
Temperatures in hot process soap making
In cold-process soap making, you keep a close eye on the temperature of both the lye solution and the base oils. You mix them typically between 100-130°F (38-54°C) and then bring it to trace, and pour the soap batter into the mold. The soap can even heat up on its own afterward, and if you use enough water and insulate it, cold-process soap can reach up to 180°F (82°C). At least for a short time before it gradually begins cooling.
Most hot process soapmakers aren’t as meticulous about temperature, at least, not until the end of the cooking process when they want to add fragrance and other additives. Slow cookers vary, but the typical model cooks at 165°F (74°C) on low and around 200°F (93°C) on high. This range is ideal for pushing soap through saponification when the heat is steady and prolonged. Cooking a batch of hot process soap usually takes between 30-60 minutes.
When you make a lye solution, it can reach up to 200°F (93°C), as can oil melted on high in a slow cooker. If you bring them together to trace at this temperature, then strange and unfortunate things can happen, including odd soap textures and even volcanos out of the slow cooker. The constant heat from the slow cooker at a high temperature can also contribute if the soap batter is already very hot.
That’s one of the ways that I’ve structured this recipe in a way that mimics a cold-process soap recipe at first. Keeping temperatures lower at first can help ensure success for the beginner. I feel that it also makes the process more comfortable for the cold-process soap maker.
Water amount in hot process soap making
When you cook soap in hot-process soapmaking, there will be water evaporation—a small and undiscernible stream of steam from the air vent in your slow cooker’s lid. If there’s too much water lost, then the soap at the cook’s end will be challenging to work with.
That’s why hot-process soap recipes need to use full-water amounts. Standard recipes call for the water amount to be 38% of the amount of base oils used by weight. You can also create a lye solution with a 25% lye concentration – a ratio of 1:3 by weight, lye to water. For example, 100 g lye would be mixed with 300 g distilled water.
Many soapmakers prefer to work with a specific lye concentration vs. the more traditional method of calculating water based on the recipe’s oils. Either work, though.
I’m using the traditional method in this recipe but have calculated for part of the water amount to be yogurt. Hot process soapmakers often add a bit of yogurt after the soap has cooked and cooled and swear by its ability to make the soap both creamy in texture and more fluid. If it has active cultures, it could help the bars harden quicker, though this is debatable.
If you’d like this recipe to be vegan, you can replace the yogurt with the same weight of distilled water.
Moisturizing hot process soap recipe
It’s time to get cooking! Now before we jump into this simple hot process soap recipe, let’s talk about ingredients. The coconut oil you use should be refined, but the more expensive virgin coconut oil will do if you can’t find it. Castor oil is a thick and sticky oil that is common enough in beauty care and helps create stable lather in handmade soap. There are several types of olive oil, including extra virgin, pomace, and mixed types. All will work, but the final bars may vary in color.
Mango butter is our luxury superfatting oil in this recipe, and it is incredible for soap and skincare. Combined with the other oils, it gives this soap recipe its creamy yet bubbly and cleansing lather. The moisturizing aspect of soap made from scratch comes from its natural vegetable glycerin content — it makes a world a difference!
One of the biggest questions I get is whether you can substitute oils in soap recipes. If you’re wondering that too, please read how to change and customize soap recipes. Lastly, if you’d like to see how to make hot-process liquid soap, I have a recipe for that too. It’s more advanced, though, so I recommend you make this moisturizing hot process soap first.
Simple and Moisturizing Hot Process Soap Recipe
- Stainless steel pan for melting the solid oils
- Rubber gloves
Prepare your Soap Making Station
- Ensure that your kitchen workspace is clean and set up with all of your tools, ingredients, and equipment. Please also prepare yourself by wearing long sleeves, closed-toe shoes, goggles, and plastic gloves. Soap making is fun but also chemistry so you need to work safely. I'd also advise that you make soap when smaller children aren't around put pets in a closed room somewhere. It's best to work undistracted, and you want to keep them safe.
- Plug the crockpot in and turn the heat to high.
- Pre-measure all of your ingredients. The solid oils into a saucepan, the distilled water into a heat-proof jug, the lye into another jug (or glass jar), the essential oils into a small ramekin, the yogurt into another ramekin, and the additional mango butter we're using as the superfat into a third ramekin.
Make the Lye Solution
- Put on your goggles and gloves, and make the lye solution. You should do this in a well-ventilated area and try not to breathe in the steam. I like to work outisde for this step or next to an open window. Measure the sodium hydroxide (lye) into a container and the distilled water into a heat-proof jug.
- Pour the sodium hydroxide into the water and stir very well. It will be very hot at this point so be careful. Set the jug someplace safe and leave the lye mixture to cool to around 120°F (49°C). You can set it in a sink, basin, or large bowl filled shallowly with water. If it's winter, it could be enough to set it in a safe place outside.
Melt the solid oils
- Though you can melt the solid oils in the slow cooker, it takes a long time. To speed things up, place the pan of solid oils on the hob and turn it on to the lowest heat setting. They will melt quicker than you expect, so stay with the pan, moving the oil around in the pan to help speed up melting. When there are a few small pieces of solid oil still floating, take the pan off the heat and set it on a potholder. They'll melt with the residual heat and some gentle stirring with your spoon/spatula.
- When completely melted, pour the oil into the slow cooker. To minimize air bubbles getting in, try pouring the liquid oils onto a clean spatula held over the pan of oils. Do this each time you add something new to the slow cooker.
Add the liquid oils
- Next, pour the liquid oils into the slow cooker with the melted oils. Use the spatula to get every last drop out of the jug then stir the oils together gently.
- Take the temperature of the pan of mixed oils. You're aiming for around the same temperature as the lye solution, but they can be a few degrees within 120°F (49°C)*.
Bringing the Ingredients to 'Trace'
- When the temperatures are right, pour the lye solution through the sieve and into the oils. If you want to minimize air bubbles, set the immersion blender in the crockpot at an angle and slowly pour the lye solution somewhere along the head-end.
- Carefully place the head of the immersion blender (stick blender) into the oils. Insert it at an angle so that any air inside the head can escape as you submerge the head. Air trapped inside the head can create air bubbles in your soap.
- The next step, bringing the ingredients to trace, is best shown in the video at the bottom of this recipe. Have a watch to understand all the steps better, but especially this one. If you're a cold-process soapmaker, this step is exactly the same as bringing the soap to trace for that method.
- Stir the contents of the pan gently, using the immersion blender as a spoon. Then bring it into the center of the pan and hold it against the bottom of the pan. Not moving the immersion blender, pulse for a couple of seconds. Then gently stir. Keep repeating this pulse then stir process until the soap thickens to a medium trace -- it will have the texture of warm pudding. Stop blending, tap off the immersion blender's head, and put it aside. You will not use it again.
Cooking the soap
- The next step is cooking the soap. Turn the heat setting on the crockpot to low, and using your spatula, gently scrape all the soap residue from the sides down into the main batter. If you don't, this thin layer can turn crusty pretty quickly. Next, place the lid on and leave it to cook for thirty minutes. Do not take the lid off during this time or it will release moisture. You need your soap batter to be fluid for the next steps.
- Over the half-hour, the soap batter will begin to puff up a bit around the edges and its texture will change. The soap in the middle will appear opaque and creamy, whereas the hotter soap on the outside will look glossier and more vaseline-like. You're aiming for all of the soap to have the glossier texture.
- After the time is up, look through the lid of the slow cooker. If you see an opaque center still, keep cooking, and set a timer for fifteen minutes. Slow cookers vary so while it takes my model 45 minutes to cook the soap, others might take less or more time.
- Once all of the soap batter resembles vaseline, you can turn off the heat, take the cooking vessel part out of the slow cooker, and set it on a potholder. Gently stir the outside edges towards the center and mix well but avoid stirring any crusty bits into the soap. They'll show up in your final bars as white lumps. Take the soap's temperature next. It will be very hot, and you need it to be just under 180°F (82°C) before you add your next ingredients. While the soap is cooling, it's best to keep the lid on the vessel. It slows down the cooling time, but it also keeps the moisture in the soap from evaporating out.
- Just before the soap is cooled enough, melt the mango butter superfat. You can use the same pan that you used earlier to melt the other solid oils.
After the cook
- When the temperature of the cooked soap is right, stir in the melted mango butter, the essential oil, and the yogurt. Mix it in gently but thoroughly.
- Spoon the soap batter into the silicone loaf mold while it's still fluid. After each spoonful, tap the mold to settle the soap and to help release any trapped air bubbles. This batch should fill a 28 oz loaf mold perfectly -- the inner dimensions of mine are 8x3.5x2.5"
- Leave the soap to cool and harden for at least twelve hours. Afterward, measure and cut the soap into bars of whatever size you'd like.
- Though hot process soap is technically ready to use immediately, it's better if you cure it for at least a week or two before using it. This allows the excess water to evaporate out but if you can wait six to eight weeks or more, then the crystalline structure of the soap will have had more time to form. It will make the soap lather and feel better when you use it. Most people aren't aware that the older soap is, the better it can get.To cure your soap, set the bars on a piece of grease-proof paper (or baking paper), in an airy place out of direct sunlight. Leave the soap there to dry out and to help excess water to evaporate from the bars.
- After the cure, use the soap or wrap it up in these eco-friendly soap packaging ideas and give as gifts. Your soap should be stored in an airy place until you use it, and to find its shelf-life, look at all of the bottles of ingredients you used. The closest date is the best-by date of your soap.
- Watch the full video below to see step-by-step how to make simple and moisturizing hot process soap.