Yesterday I had the fortune to successfully attempt a soap I infused with fresh papaya, guava and kiwi in a base of mango nectar. I know there’s not a lot of information out there about how to successfully make fruit soaps, so I thought I’d share my experience in the hopes that it might help a fellow soapmaker! Fresh fruit is a great additive to soap as it adds a ton of beneficial vitamins, antioxidants and moisturizers. It also adds a touch of the exotic, and can add to the complexity of the fragrance of the soap.
First thing: choose the fruits you want to use, making sure to think about water and sugar content. Kiwi for instance is very watery, and juices very easily. Guava and papaya are more fleshy. You don’t want to add too much watery fruit without considering adjusting the amount of overall water content in your soap. The sugar is important too, as the heat from the reacting soap can cause the sugar in the fruit to caramelize or even burn—a process which can make your soap seize or cause an unpleasant odor or color.
With a fruit soap I recommend a much higher liquid content than normal. I used ~38% liquid content, which was a combination of water and mango nectar. You should always dilute your liquid somewhat with water if its high in sugars to help buffer against the effects of lye. The sugars can burn very easily, so as always make sure you prepare everything slowly and at cold temperatures.
I also recommend the addition of a little bit of stearic acid (~5%) to help firm the soap once its done. With the high water content and additives you’re going to want to make sure that it doesn’t take a billion days to cure and will cut easily.
Second thing: Prepare your fruit mixture. The one thing you don’t want is chunks of fruit in your soap. Chop and deskin your desired fruit into small chunks then use a blender or food processor to pulverize it until it is exceedingly fine. You want to make sure there are no chunks, membranes or stringy pieces (ehem, mango, I’m looking at you!). You can either remove anything like this you find or continue to blend it. I used a Blendtec blender set on ‘Fruit Juices’ to make sure my fruit blend was extra smooth. I also added about 100g of mango nectar to make sure it blended properly. It should have a semi-solid, watery consistency like baby food. Stick your mixture in the fridge. You’re going to want it nice and cold when you add it to your soap!
Third thing: Prepare your oils and your lye mixture like normal. If you’re adding juice to your lye, make sure it is very cold. You’re also going to want to add it much slower than usual with a much colder ice bath. Don’t let the temperature in your lye mixture exceed 120F. This will take some patience, I realize, but it will mean the sugars in your juice/lye mixture don’t burn and your mixture doesn’t solidify on you.
At this step make absolutely sure that all your additives including fragrance, colorants, exfoliants, etc. are ready to go as soon as you need them. You’re going to want to make sure you can immediately start pouring in what you want without waiting around and measuring things out because this kind of soap will trace quickly.
Let your oil mixture and your lye mixture cool to 85-90F. It will heat up quickly as you add the lye mixture to your oils. Mine went through false trace and seized briefly before becoming more liquid again. (Note: Do this if you’ve added juice to your lye mixture, otherwise a temperature range of 95-100F should suffice). Just keep stirring and slowly adding your lye mixture until its fully incorporated. It would also be a good idea to check the temperature occasionally just to make sure its not getting too hot. If you’ve added your ingredients at a low enough temperature it shouldn’t be a problem.
Fourth thing: After you’ve mixed your lye and oils, add your fragrance and additives (remember to reserve some of your oils to add your fragrance to before you pour it into your soap mixture—this will keep your essential oils from volatilizing too quickly and allows you to control the superfat oil somewhat, as well as keep the soap from seizing upon the addition of reactive oils like orange). Then slowly add your cold refrigerated fruit mixture to the soap mixture. I recommend hand stirring at this point to keep the soap from thickening prematurely.
After that go ahead and pour the soap mixture into your mold and you’re done! Don’t insulate this soap since it will get hotter than most. You want to give it every opportunity to cool off to prevent it from cracking or boiling from the heat.
I hope this helps any future fruit soapmakers out there. If you have any questions, feel free to leave a comment!