Developing a Soap Recipe

When I was learning how to make soap, I felt completely overwhelmed by all the information out there. Some recipes are in ounces, others are in grams. Some throw in tablespoons and teaspoons for good measure (ha!). Superfatting is baffling. There are 937 lye calculators out there. Am I an evil person if I use palm oil?

My blog is my space where I sort through information and try to demystify DIY so today, I want to talk a little about developing recipes. I’ve been trying to think of a way to make soaping a little easier for people who don’t have the perfect sized mold or are missing an expensive oil but want to re-work the recipe into something they can use.

Like many good things in life, it all comes down to math. When you’re making soap, the difference between good math and bad math can be a really nice bar and one that burns your skin off. Not really a chance that most people are willing to take, I’m thinking. With all that in mind, this is a step-by-step guide to making your own soap recipe.

1. Determine the capacity of your soap mold in grams or ounces by filling it up with water and weighing the water. Don’t forget to tare the weight of the mold.

2. Calculate how much liquid and total oil you’ll need. This will be determined by what liquid you decide to you to dissolve lye. As a guideline, waters use a 1:3 water to oil ratio where as milks use a 1:2 ratio. Although this is a useful rough estimate, always use a lye calculator to make sure that your recipe will be safe.

  • Waters (1:3 ratio)
    • Aloe
    • Beer (freeze first)
    • Coconut water
    • Rosewater
    • Tea
    • Water
  • Milks (1:2 ratio, freeze first)
    • Almond milk
    • Buttermilk
    • Cow’s milk
    • Goat’s milk

Once you’ve chosen a liquid, you can move on in your calculations. I think best visually, so I use charts when I do the math. Let’s use one of my molds as an example. My mold holds 36 oz of water so I put that number in box A2. The recipe I’m using in this example uses water to dissolve the lye, so we’ll use a 1:3 ratio. That means that 75% of the oil/water will be oil (box B2). All that’s left to do is multiply across the row to find out how much water you’ll need in your recipe.

1 Mold capacity Percentage  Result
2 Water 36 oz 25% 9 oz
3 Oil 36 oz 75%  27 oz

3. Come up with your oil recipe. This is the science part. Check out my page on soap making lipids to make sure you’ve got the right balance of moisturizing, cleansing, hardness, and bubbles.

Note sure where to start? Try soap queen’s favorite recipes or tips for formulating your own recipe.

Here are some of my bases:

  • Mamoot (1 august 14)
    • 59% olive, 40% coconut, 1% shea
    • Nice and hard, good bubbles, a little drying
  • Mamoot (25 may 14)
    • 70% olive, 20% cocnut, 8% avocado, 2% shea
    • Nice suds, but melts quickly and took days to unmold
  • The Nerdy Farm Wife (4 october 14)
    • 68% olive, 25% coconut, 7% castor
    • Very easy to cut and stamp, bubble and smooth
  • Mamoot (10 december 2014)
    • 30% olive, 30% coconut, 30% palm, 5% castor, 5% avocado
    • Nice and hard the next day, easy to cut and stamp
  • Mamoot (10 december 2014)
    • 30% olive, 30% palm, 20% coconut, 5% sunflower, 2.5% castor, 2.5% avocado
    • Still soft the next day, very hard to stamp and cut cleanly
  • Mamoot (11 december 2014)
    • 32% olive, 32% coconut, 32% palm, 4% sweet almond

To work with percentages in recipes, I use charts again. Let’s do another example. Remember how we found how out how much oil we’ll need in our sample recipe in box D3 above? Let’s put that number in each box in column G.

1 Oils 27 oz
2 Olive oil 67% x 27 oz = 18 oz
3 Coconut oil 26% x 27 oz = 7 oz
4  Castor oil 7% x 27 oz = 2 oz

4. Run your oil recipe through a lye calculator to see how much lye you’ll need. I usually go for 5% because it’ll make a bar that’s not so soft that it melts in the shower but still in a safe level.

5. If oils are the science, this is the art part. Create a bar recipe by adding scents, exfoliants, colorants, and other additives. Unless the ingredient mentions otherwise, these parts are added after the soap has reached trace.

  • Essential oils – Expensive, yes, but worth it in my opinion. They give crispy, unchanging scents and are easily predictable as to what they’ll do to the soap.
  • Fragrance oils – Honestly, I’m not the biggest fan of fragrance oils. I’ve tried a few and they’ve all been so heady that I’ve had to leave my windows open for hours afterward to make my headache go away. I’ve also found that most smell very different in the bottle and after saponification. Plus they’re not much cheaper than essential oils.
  • Citrus zest
  • Cinnamon
  • Coffee grounds – If you don’t think you’ve added enough, STOP. You probably have. Coffee grinds really are lovely in moderation but painful in excess.
  • Cornmeal
  • Oatmeal – Grind it up so that it doesn’t clog your shower drain
  • Powdered or crushed nuts
  • Seeds – poppy, chia, flax, cranberry, strawberry
  • Tea bag contents
  • Red/Pink
    • Australian pink clay
    • Australian red reef clay
    • Brazilian red clay
    • French red clay
    • Moroccan red clay
    • Red oxide
  • Orange
    • Paprika
  • Yellow
    • Brazilian yellow clay
    • Buriti oil
    • Carrot Baby food – Only ingredients can be vegetable/fruit and water; to use, replace half of your liquid with baby food and combine it with lye at the beginning of the recipe
    • Turmeric
  • Green
    • French green clay
    • Green oxide
    • Spirulina
    • Zeolite green clay
  • Blue
  • Purple
    • Alkanet root
    • Brazilian purple clay
  • Pink
  • White
    • Kaolin clay
    • Titanium dioxide
  • Grey
    • Bentonite clay
  • Black
    • Activated charcoal
    • Australian black clay
  • Brown/Tan
    • Cocoa
    • Pumpkin Puree – Replace half of your liquid with baby food and combine it with lye at the beginning of the recipe
Other Additives
  • Clay – Provides slip; good for shaving soaps
  • Dried flowers
  • Honey – A humectant
  • Spices

6. Take notes. You’ll only get better as you make more soap so you might as well start noting now what works and what doesn’t.

Soap Making Lipids

Properties – The tricky thing about soap making is that it almost always takes more than one type of oil to get a good bar of soap. Some are very moisturizing but aren’t so great at scrubbing off dirt. Others are great cleansers but will leave your skin feeling tight. Some last forever while others will spoil in just a few months. Try combinations of complimentary oils to get the right balance.

Bar density – A really soft bar of soap won’t last long in a humid shower, but a rock-solid piece of soap can scratch your skin.

Suds – Soap bubbles are usually described on a continuum from bubble to creamy. Occasionally certain soaps can even feel waxy, sticky or slimy. A good bar will be bubbly enough to froth up but creamy enough to stick around when you start washing.

Trace – Different fats come to trace different. Some are incredibly fast and require cooling so that the mixture doesn’t seize up when lye is added. Others won’t get thicker than cake batter, so you can save yourself some time and wrist pain by knowing ahead of time. The goal of trace is to get your oils and lye water to mix enough that they won’t separate when the soap sits.

Special instructions – Just what it sounds like. The density, bubbliness, self-stability, and moisturizing qualities of the oils often means that you don’t want to use too much in a recipe.

Melting point – Knowing the melting point of oils can help you plan when to scoop them into your double boiler so that no oil has to cook longer than necessary.

Fatty acids – All fats are made of triglycerides which are, in turn, made of fatty acids. Knowing the fatty acid composition of a certain oil can be beneficial when you’re wondering why one oil acts or doesn’t act like another or if you’re looking for something similar to an oil you don’t have on hand.

Saturated fats

 Lauric  hard, cleansing (too much can be drying), bubbly lather
 Myristic  hard (but softest of the saturated fats), cleansing (too much can be drying), bubbly lather
 Palmitic  hard, cleansing (too much can be drying), creamy lather, long life
 Ricinoleic  soft, conditioning, creamy lather
 Stearic  hard, creamy lather

Unsaturated fats

 Linoleic  conditioning, silky, short life
 Oleic  conditioning, slippery, long life

SAP value – The saponification value is used to calculate how much lye is needed to react with 1 gram of the fat. Lye calculators do the same job, but if you want to do it by hand, this is all the information you need.


I know that this chart is damn near impossible to read. I’m open to any HTML/Wordpress tricks to make it skinnier


Oil Name Properties Bar Density Suds Trace Special instructions Melting Point Fatty Acids xxxxxxxxxxxxxxx Shelf life SAP Value
Avocado Oil Vitamins A, D, E, many unsaponifiables, moisturizing Very soft Creamy Good for superfatting 0ºF 58% oleic, 12% linoleic, 20% palmitic 1 year .132
Beeswax Hardening 145ºF Forever
Castor Oil Moisturizing, humectant Soft Bubbly, creamy Thick, fast, can be slower with a low temperature 5-10% max 0ºF 90% ricinoleic 1 year .127
Cocoa Butter Vitamin E, antioxidants, cleansing Hard Creamy Thick 15% max 95ºF 30% stearic, 27.5% palmitic, 32.5% oleic 1-2 years .136
Coconut Oil Very cleansing, too much can be drying Hard Bubbly, semi-creamy 20% max 77ºF 48% lauric acid, 19% myristic, 10% palmitic > 1 year .178
Grape Seed Oil Increases slipperiness, moisturizing Soft Creamy, sticky 5-10% max; not great to use 14ºF 65% linoleic, 23% oleic 3 months; 1 year refrig. .134
Jojoba Oil Liquid wax, moisturzing, shelf stable, many unsaponifiables Very soft Creamy Slow, thin 10% max for hardness; good for superfatting 50ºF 72.5% eicosenoic, 15% erucic Forever .064
Lanolin Soft 100ºF lanolin .070
Mango Butter 15% max 90ºF 45% oleic, 44% stearic 1 year .134
Olive Oil Moisturizing Soft, slimy Creamy Thin, faster with lower grade Up to 100% 21ºF 75% oleic, 15% linoleic, 10% palmitic 2 years .133
Palm Oil Low glycerin yield, cleansing Hard Creamy Fast 30% max ºF 44% palmitic, 39% oleic 1 year  .142
Rice Bran Moisturizing, similar to olive Hard Creamy Up to 100% ºF 43% oleic, 26% linoleic, 22% palmitic 1-2 years
Safflower Oil Moisturizing Soft Slimy 20% max 2ºF 75% oleic, 15% linoleic 1 year .135
Sesame Oil Earthy smell, moisturizing Hard 10% max 21ºF 45% oleic, 40% linoleic 6 months – 1 year .135
Shea Butter Moisturizing Hard Creamy Fast, thick 15% max; Good for superfatting 95ºF 47% oleic, 43% stearic 1 year .126
Soybean Oil Moisturizing, cheap, short shelf life Hard Creamy, sticky 20% max 3ºF 50% linoleic, 30% oleic, 11% palmitic 3 months refrig. .134
Stearic Acid  Not very cleansing Very hard Waxy Fast 5% max 70ºF 100% stearic .147
Sunflower Seed Oil Short shelf life Soft Slimy 20% max 1ºF 72% lineolic, 16% oleic 3 months refrig. .134
Sweet Almond Oil Moisturizing Soft/Hard Creamy, silky 12.5% max; good for superfatting 0ºF 70% oleic, 20% linoleic 6 months – 1 year .137

The History of Soap

Many many years ago, there was a mountain near Rome called Mount Sapo. In honor of the goddess Athena, the people from neighboring towns would carry goats and sheep to the top of the hill and burn them atop a sacrificial fire. As the animal fat melted and mixed with the alkaline ash, soap formed and was later carried to the stream below by rain. The women in the towns did their laundry in this stream, finding that their clothes got cleaner at Mount Sapo than anywhere else.
Continue reading

Oatmeal and Lavender Soap

5.5 oz coconut oil Coconut oil gives your soap moisture, big bubbles and a harder bar. I buy mine at Trader Joe’s or Costco, but it’s pretty trendy right now so you can find it just about anywhere.
8 oz olive oil Olive oil gives a dense creamy lather and a soft bar.
4 oz water Water is used to dissolve the lye. It will evaporate as the bar sets.
1.97 oz lye You already know what lye does, but you might not know where to buy it. Check the drain-unclogging chemicals sold at at Lowe’s or Home Depot. As long as it’s 100% sodium hydroxide, you’re good to go.
1/4 t honey Honey is a natural humectant and will keep your skin soft. It won’t dissolve into your soap, so don’t add too much or you’ll end up with honey bubbles and oozy soap.
5 drops lavender essential oil Lavender oil is calming and helps keep itching from dry skin at a minimum.
1 t shea butter Shea butter is incredibly moisturizing. If you don’t want to buy any, you can add a teaspoon of any oil or butter.
1 T oats Oatmeal soothes dry skin and scrubs off dead skin. Grind it up fine (I used my magic bullet because I’m fancy) so that it doesn’t clog your drain.

Saponification Station

Soap is the metallic salt of a fatty acid. What in the world does that mean? Well, in chemistry, salt isn’t just the white stuff that always hangs with the pepper, it’s any product that comes from neutralizing an acid and a base. Let’s take kitchen salt (sodium chloride) as an example. When you combine hydrochloric acid (HCl) with sodium hydroxide (NaOH), you get sodium chloride (NaCl) and water.

HCl + NaOH –> NaCl + H2O

This is particularly cool because hydrochloric acid is crazy acidic (it’s the stuff that your stomach uses to break down food) and sodium hydroxide is suuuuper alkaline (remember the scene in Fight Club when Brad Pitt burns that ugly hole in Edward Norton’s hand? That’s lye AKA sodium hydroxide) which means achtung, baby! Put them together, though, and you get two completely safe and consumable substances.

Making soap – or saponification, if you’re savvy – is pretty much the same thing. Add lye to an oil and you get a salt that we call soap! More specifically, you combine a trigylceride with lye and end up with soap and gylcerine.


You already know what lye is, but what’s about triglycerides? As it turns out, all the oils we’re familiar with are different types of triglycerides. If you look at the formula for triglyceride, you’ll notice there are some R’s up in there. Those R’s stand for fatty acid radicals, three of which are combined to create a single type of oil. Olive oil, for example, is made up of two oleic acid radicals and one palmitic acid radical. Because of their chemical makeup, different oils and fats have specific properties that can be helpful or harmful in soap making. We’ll talk more about this when we get to the recipe.

The glycerin that’s a byproduct of the reaction is one of the best reasons to make your own soap. Glycerin is a humectant (a thing that keeps moist things moist) and makes your skin soft and moisturized. Often, store-bought soaps have been stripped of most of their glycerin, which is then sold to be used in more expensive bath products.