Now that you've made a batch or two of single oil soap, it's time to up your game and mix oils together. Blends combine the skin-nourishing benefits of different fats and their soapy characteristics. I love playing around with various oil combinations and seeing how each turns out. In this tutorial, I'll take you step by step through the process of making multiple oil bar soaps using the cold process method. It's fun and easy!
New to soap making? Start with Cold Process Basics to get a little more foundation. Then, get some practice with Single Oil Soaps.
Today, I'm making a blend of four oils: castor, sunflower, avocado, and olive. Each of these ingredients brings something different to the table. Castor seed, a light easily-absorbed oil, makes a soft soap and is known for lots of lather, along with some great conditioning and moisturizing properties. Sunflower, a light healing oil, is another soft soap, offering a medium lather, and is great for moisturizing and improving skins' appearance. Avocado, a heavy rich oil, makes a soft soap with fluffy lather, and is amazingly nourishing and moisturizing for the skin as it's high in vitamins (especially vitamin E), minerals, and amino acids. Olive oil makes a very hard final soap (which will off-set the softness of the other oils), and although not much of a lather producer, it's a good cleanser, helps repair damage, and is very gentle on sensitive skin.
Real soap has a shelf life...
You may not realize that the decorative hand-made soap you bought at that cute little boutique when you were on vacation ten years ago and never used, may not be good anymore. Excess oils in soap can go rancid and different oils have different life expectancy's. If you have an old bar that looks moldy or discolored, or is emitting a bad odor, it's time to toss it. Keep in mind that commercial "soaps" may not be soap at all or may have ingredients meant to extend shelf life. But true natural soap, like everything else in nature, breaks down at one point or another. As a rule of thumb, homemade soaps have a life of around two years. Although the higher the superfat, the lower the life expectancy. Most of the oils I'm using have a decent shelf life, however, sunflower oil has a much lower one because of it's fatty acid structure. However, the high level of vitamin E in the avocado oil may act somewhat as a preservative to off-set this. Regardless, we plan on using these soaps within the year anyway. If you're making soaps for you and your family, small batches are the way to go. Just make more before you run out.
Now to make some soap!
Let's gather the things we need: ingredients, equipment, and some basic knowledge.
Ingredients
1.6 oz castor oil
1.6 oz sunflower oil
3.2 oz avocado oil
9.6 oz olive oil
2.0 oz lye (sodium hydroxide, aka: soda ash)
6.0 oz distilled water
Note: The amount of oils in this recipe equals 16-ounces which I have found makes a batch of 6 standard rectangular soap bars. Depending on the size and shape of your molds, you may end up with more or less bars.
How the heck did I figure out how much lye to use?
Each oil has what's called a SAP value that determines how much lye is needed to completely saponify one gram of that particular fat. Today's recipe is made with a 5% super fat, which is the percentage of fat leftover after all the lye has been transformed into soap. If the superfat is too high, the soap will be softer and is likely to become rancid easier. Too little and the soap will dry out skin and possibly even burn if there is un-transformed lye still present. Having the right amount of superfat balances these issues while providing moisture and improved lather. I like 5% superfat for a hand / body soap. It provides enough moisture so skin doesn't dry out, at the same time it creates a very firm bar. If you're interested in Creating Your Own Soap Recipes, then you'll also need to know All About SAP Values.
Making multiple oil soap is exactly like making single oil soap. The only difference is in calculating the lye. Start by figuring out the lye needed for each individual oil. Then add those lye amounts together. Avocado has a SAP value of 0.148. When multiplied by how much of the oil I'm using, I get 0.474 ounce of lye needed (rounding to the nearest thousandth) for just the avocado oil. Castor oil's SAP value is 0.129. So, I will need an additional 0.206 ounces of lye. Olive oil's SAP value is 0.135, adding another 1.296 ounces lye. And finally, sunflower oil, with a SAP value of 0.136, needs 0.218 ounces of lye. When I add all of these together, my total lye needs equal 2.112 ounces of sodium hydroxide (lye). Remember that this gives me a lye discount (or superfat) of 0%, where no fatty acids are leftover. But I'm making a 5% superfat soap! So, just a little more math... Taking the total I just calculated for the lye, I will multiply it by .95 to get 2.006. Because my scale only goes to the tenth place, I will further round to get 2.0 ounces of lye needed for this recipe. Where did the .95 come from? 1 – the amount of desired superfat. To get a full understanding of this equation, I really do recommend my article on Creating Your Own Soap Recipes (which also covers how I get the water amount).
Equipment
kitchen scale – exact measurements are required
double boiler – this can just be a pot inside a larger pan filled with water
mixing bowls – a large bowl, a medium bowl, and one smaller bowl; use only stainless steel or ceramic for mixing
thermometer – a glass candy or steel meat thermometer works, although nowadays I use either a digital probe or sometimes a laser thermometer
stirring spoon – use a stainless steel mixing spoon, not wood
mixing tool – you can use a whisk, although an electric hand held immersion stick blender cuts mixing time dramatically
soap mold – molds come in all shapes, sizes, and materials; I like silicon molds which makes it easier to get the soap out
Remember: Soaping equipment should be used solely for making soap (except maybe the kitchen scale and double boiler). You definitely don't want anything that touches the lye or lye solution to be used for food.
On to the basic knowledge...
Alright, we've gathered our ingredients and set out our equipment, now the fun part!
Step one: Safety first.
Since sodium hydroxide (lye) eats stuff and will burn your skin on contact, safety gear and cautionary methods are important in protecting yourself (and your kids if they're helping). When working with lye, be careful not to splash it on you, get any in your eyes, or breathe in the fumes from the lye solution. Also, make sure the area is clear of pets. Here's the safety gear checklist:
long sleeve shirt
long pants
shoes that cover your toes
rubber kitchen or cleaning gloves (I use nitrile gloves)
safety glasses or chemistry goggles
mask (a basic dust mask works fine)
spray bottle of vinegar (vinegar neutralizes lye, thus having a spray bottle on hand just in case you do happen to get some on you is highly recommended)
Step two: Measure everything.
Everything needs to be measured exactly for your soap to turn out right. Start by weighing out the fats and combining them in the inner pot of the double boiler. A total of 16 ounces of oil is going into my pot for this soap. Next, I'm weighing out 6.0 ounces of distilled water into the medium bowl and, finally, 2.0 ounces of lye into the smallest bowl.
Step three: Heat the fat.
On the stove, fill the outer pan of the double boiler at least halfway with water. Over medium-high heat, use the thermometer to bring the oils' temperature up to about 140 degrees. This is 10 degrees higher than what it should be when mixing with the lye, but going over will allow time to make lye water (next step). When measuring temperature, be sure the thermometer is in the middle of the pot and not touching the bottom or sides.
Multiple oil tip: When using multiple fats to make soap, be sure to mix the oils together well. I whisk thoroughly for a minute as the oils are heating. This ensures there are no odd spots and that shorter shelf life oils will combine with longer ones.
Step four: Make lye water.
Caution! For this part it's important to be in a well ventilated area with safety gear on. Very slowly add the sodium hydroxide to the bowl of water, stirring carefully with the mixing spoon. Remember: never add the water to the lye; always add the lye to the water to avoid splashing. When lye comes in contact with water it can reach up to 200 degrees! Be careful, this will heat up the bowl. Slowly stir until all the lye is dissolved.
Step five: Bring it all together.
The oil and lye solution should both be about 130 degrees when combining together (make sure they are no more than 10 degrees apart). Just like when making the lye water, never pour anything into the lye. Instead, pour the heated fats into the largest mixing bowl first, then very slowly, pour the lye water into the fat. Use a mixing spoon to gently stir the solutions together. Continue stirring until the entire solution is murky.
Step six: Mixing it up.
Be careful not to splash during this step. If using a whisk, work around the bowl in a brisk figure-8 pattern. For the immersion blender, place the blade tip all the way into the solution before turning it on to avoid splattering, then move it around inside the mixture. I'm using the immersion blender – which is so much quicker than hand-whisking – and within about 10 minutes my multiple oil soap begins to thicken and reach what we call "trace". Find "trace" by using the mixing tool to drizzle a little of the soap across the top. If it leaves a distinct trail for a few seconds, then your soap is ready for the next step.
Step seven: Finishing touches.
Once trace has been reached, it's time to pour the soap into molds. If you were to use colors, scents, or any other additives, this is the time that you would mix those into the soap before pouring. But, my soap today is additive-free and all-natural, so it's going strait into the molds. I'm using a ladle which makes filling individual bar molds easier.
Step eight: Setting the soap.
Soap needs enough time in the molds to solidify its shape. Depending on the oil used and environmental factors, this could be an hour or few days. I usually let most soaps set over night, although some soaps may need longer. If a bar is especially soft when removing it from the mold, then wait. The bars I'm making today are especially soft, so I'm giving them 2-3 days in the mold.
Step nine: Time to cure.
It takes time for all of the lye to totally convert into soap and for the bars to harden completely. I find that most bars are ready between 4-8 weeks. To cure, remove the soap from the molds and place the bars in a dry, dark-ish, and airy location. I use a wire drying rack for maximum air flow, but you can set them on any kind of tray. Be sure to flip them over from time to time. Olive oil is the primary fat in my bars and it takes longer to cure, so I'll be waiting a full 8 weeks for these beauties to be ready.
Step ten: It's soap!
These lovely little bars are now ready to lather up. I'm taking one of my multi-oil bars and putting it directly into my soap sack in the shower. The rest are going into our soap drawer. When storing soap, don't use plastic containers or cling wrap because over time soap releases moisture and plastic will keep the moisture from evaporating which can cause soap to get funky. Paper, fabric, or just open air are great ways to keep your soap dry.
Don't forget my pro tip!
I store my soaping equipment in a large tub. After I'm done making a batch of soap I put all the used dirty equipment into the tub, then put the lid on (this keeps pets and kids from getting into lye remnants). In a day or two, after the mess has saponified and neutralized, I then put it all into the dishwasher, except rags which go in the laundry with kitchen towels. The only exception is that many molds should be washed by hand and not put in the dishwasher. After rinsing out the tub, just put it all back in to store for next time. Clean up made easy.
The 10-step process above is the same no matter what oils you use. Just remember that because every fat has a different SAP value, the ratio of lye to oil will be different for each. Time to trace, set, and cure will also vary. As always, I encourage you to play around and try out different recipes to see what you like best.
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