Complete Guide to Natural Soap Additives and How They Work

A comprehensive introduction to natural soap additives and the reasons that we add them to natural cold-process soap recipes. Includes natural soap colorants, fragrance, exfoliants, scent fixatives, and when to add citric acid and sugar to soap recipes.

In its purest form, natural soap requires just three ingredients: fat, lye, and water. The fat can be vegetable oils, butters, or waxes, and there are many types to choose from. You can also make soap with animal fat or waxes, such as lard, tallow, or beeswax. In most cases, a natural soap recipe includes three or more fats combined with the correct amount of lye and water needed to transform the fat into gentle soap. Often part of the fat used in a recipe is called the superfat, which is also a requirement. Any other natural soap additives that form part of the recipe are optional.

I get a lot of questions from people on the cold-process soap recipes that I share. Mainly, how to change or customize the recipe but also questions on whether they can leave an ingredient out. The simple answer to this is that the three main categories of ingredients listed above are essential. You cannot omit one of them without impacting the whole recipe (and its safeness for skin). Any other natural soap additives in the recipe aren’t necessary to make the soap recipe, except for citric acid (see further below). These optional ingredients are used to add color, scent, decoration, texture, and to improve or speed up processes.

I go through the process of making handmade soap in much more detail in the Lovely Greens Guide to Natural Soapmaking. Use it and the information below to get you started making natural soap recipe choices. Between the two, you’ll know what and why ingredients are used in natural soap making, and how to make it from start to finish.

Natural Soap Additives

Making handmade soap can be as straightforward or as complicated as you would like. It’s basically like everything else in life! Recipes and techniques can include exotic scents, intricate swirls, and all manner of expensive and sometimes bizarre ingredients. I wish that more people would ask themselves WHY am I putting this ingredient in soap rather than CAN they. That means considering the desired effect, and if the ingredient is safe, effective, or even suitable? In good design, form should always follow function, and that’s also the case with soap.

The list of natural soap additives below describes what they are and why you would add them. Essentially, their purpose in a soap recipe and why they would be beneficial. Used in the right way and in the correct proportion, they can upgrade a simple soap recipe into something fabulous! Yet, there’s a growing movement of people returning to the basics. Making pure and simple unscented soap that gently cleans and doesn’t set off allergies. It’s food for thought when you’re using natural soap additives. My advice is to keep it simple and to use them wisely.

Soap Recipes Using Natural Soap Additives

• Natural Dish Soap Recipe
• List of Natural Soap Colorants
• Natural Carrot Soap Recipe
• More Natural Soap Ingredients

Essential oils in Soap Recipes

Essential oils are concentrated and volatile plant chemicals extracted from leaves, flowers, fruit, and bark. They’re mainly extracted using steam distillation but can also be pressed or extracted using other methods. Essential oils are popular in complementary medicine, but in handmade soap, you mainly add them for scent. Types suitable for soap and their usage rates vary and are better explained in this piece, but the most common tend to be used at about 3% by weight of the soap recipe (excluding water). In some cases, the essential oil can also tint your soap.

Natural Soap Colorants

Without additives, handmade soap’s natural color tends to be an off-white to a creamy color. To color soap, you need extra ingredients, the most common of which come in a powdered form that you add to the soap either at trace or into the lye solution. You can also use natural colorants (both powdered and not) to infuse color into the lye solution or main soaping oils but then strain it out.

Clays are probably the most common and stable natural soap colorants, and they come in an impressive range of colors. When using clay, the general usage is about one teaspoon per pound (454 g) of soapmaking oils. You can add it directly to the lye solution, or you can mix each teaspoon of clay with three teaspoons of distilled water and then add it to the soap batter at trace.

You can also use many of the same botanicals used in fiber dyeing to color your soap. They include alkanet, madder, annatto, indigo, woad, calendula, turmeric, coffee, and tea. Each botanical will have a different usage rate and method, and many of them are outlined over here.

Bee propolis is another natural soap colorant, and if you’ve ever seen a propolis tincture, you’ll know why! Other natural soap additives used as colorants include charcoal, cocoa powder, spices, natural oils, and the roots, fruit, petals, and expressed oil of plants. Aleppo soap, perhaps the oldest type of soap still made, is naturally colored green with laurel berry oil. You can also naturally tint soap using some fruit purees, including carrots and avocado.

Botanical Decorations on Soap

Sometimes soap recipes will call for dried leaves, fruit, fruit peel, seeds, or flower petals, but they are not used in the same way as colorants. Instead, you use them to decorate the tops of soap bars and sometimes throughout the soap.

Use botanical decoration with a light touch, and some of the most beautiful decorations I’ve seen and used include a sprinkling of dried calendula flowers or cranberry seeds. It’s particularly effective if you add texture to the tops of your bars with a spoon or skewer then decorate it afterward with botanicals. When the soap has set, and you’re ready to cut it, make sure to turn the soap upside down and cut it from the bottom of the bar to the top. This stops the botanicals from dragging through your lovely handmade soap.

Though I love the look of botanically decorated soap, I wouldn’t recommend going overboard if you’re making soap for other people. Dried flower petals and soggy pieces of re-hydrated orange slices are a pain in the shower and bath. There’s also a concern that if they do go down the drain, they can clog it too.

Again, I have much more information on using botanicals in handmade soap in another piece. It covers the types you can use and also some challenges (such as botanicals turning brown). Some of the most common types of botanical decorations include lavender buds, rose petals, cornflower petals, dried orange slices and peel, and coffee beans. There are more exotic ingredients you can use, too, including moss and lichen.

Exfoliants in Soap Recipes

When we’re making scrubby hand soap or an otherwise exfoliating bar, we can use ingredients such as oatmeal, sea salt, luffa, coffee grounds, ground pumice, seeds, and shredded coconut. Some are more exfoliating (scratchy) than others, so again, use caution. Oatmeal is one of my favorite plant-based exfoliants, and I find that colloidal oatmeal or even quick oats, opposed to whole rolled oats, are gentler.

Poppy seeds are also a common ingredient added for exfoliation. Please be aware that the only poppy seeds you should use for skincare are the edible types from the breadseed poppy, Papaver somniferum. These are the types you’d use in baking, and the seeds are often massive. Big seeds can mean a scratchy bar of soap that some people find uncomfortable. Even though they look great, use restraint. The same goes for other seeds, such as cranberry seeds.

Another exfoliant that I use often is ground pumice. Pumice is a light volcanic rock, and you can get it in various grades, including extra fine powder. It can clump together if you add it at trace, though, so I tend to add pumice to the melted oils and stick blend them in.

Using Silk in Soap

Good natural soap has a silky feel already, in my opinion. However, some soapmakers (and sellers of soapmaking ingredients!) recommend using silk fibers and liquid silk in soap recipes. Both are made from the cocoons that silk works create to metamorphosis into moths and are not considered vegan or vegetarian. The cocoons are collected, the caterpillars killed, and the fibers used to make silk fabric and fiber.

You can dissolve the silk fiber in your hot lye solution or purchase ready-made liquid silk and add it at trace. The natural keratin in the silk adds a silky feeling, and another ingredient that some people use for the same purpose is snakeskin. Again, it’s added to the hot lye solution to dissolve and then strained when added to the melted oils. As you can guess, snakeskin soap isn’t vegan or vegetarian either, though you’re only working with the shed skin rather than harming an animal.

Using Salt in Soap Recipes

There are two main reasons to add salt to soap – to create salt bars or to help harden soap quicker. In salt bars, you add salt to the soap at trace, and the final bars have pieces of salt in them. They can be fine grains, or large crystal salts, or both. The purpose of salt used in this way is to create a soap that helps with acne, is exfoliating, has other potential “detoxing” ability, and that lasts a long time even when wet in the shower.

To make salt bars, you can use by weight 50-100% of the weight of your main soaping oils in a soap recipe. Salt affects how soap lathers, though, which is why recipes tend to have a lot of coconut oil to compensate. A high superfat of 20% is also calculated in so that the bars aren’t drying.

The second way to use salt in soap is to help speed up the soap hardening. It’s advantageous in recipes with a high amount of liquid oils, such as castile soap, since they often take a week or more to come out of the mold. Adding salt to the recipe is accomplished using brine or seawater in place of the water for the lye solution. I show how to use seawater in this soleseife recipe. When making your brine, dissolve sea salt or table salt by weight of up to 25% of the weight of your main soaping oils in the lye solution.
Sodium lactate is another ingredient used for the same soap hardening qualities. It’s the salt of lactic acid, a vegan ingredient derived from fermenting beets or corn.

Sugar and Honey in Soapmaking

There are a couple of reasons to use sugar in soapmaking – and by sugar, I mean cane sugar or honey. The first is color. If you add a small amount of either to the lye solution while it’s warm (under 150F/65C), it will caramelize, creating a lovely caramel color in your soap and a sweet natural scent. One half to one teaspoon of either per pound (454 g) of your main soapmaking oils is the right amount. Use too much or when the lye solution is too hot, and the sugar can scorch, though, just like when you’re making homemade caramel.

The other reason to use sugar in soapmaking is to boost lather. It’s helpful in recipes that are low in coconut oil or that need a bit more fluffy lather. Adding honey or sugar to the lye solution can do this but if you don’t want the color of your soap to be affected, add sugar syrup to your soap batter. Make sugar syrup by combining one cup of sugar with half a cup of distilled water and gently heating it together. Use one teaspoon per pound of soapmaking oils and stir it in at trace. Sugar can heat soap up, creating full or partial gel, so keep that in mind if you’re trying to achieve a light or consistent color.

Adding Milk to Soap Recipes

Goats milk soap is very popular in the world of homemade soap, but why? Using goat milk instead of distilled water is said to add fats, vitamins, and lactic acid to your bars and make them very sensitive and creamy. Some even say that using goat milk in soap helps with eczema and psoriasis. Milk also contains sugars, though, so when you’re using it to make the lye solution, you need to freeze it beforehand or use this simple method. Otherwise, the soap may turn brown or smell unpleasant.

Though goat milk is the norm for milk soaps, you can also use other milk, including cow milk, camel milk, sheep milk, and even human breast milk. The latter is becoming very popular in home soapmaking when mom has extra expressed milk to use herself. It could be challenging to create a human breastmilk soap for retail (legally), but it may be possible in some regions. After all, there’s a vendor of breast milk ice cream in the UK!

Fruit, Flowers, and Vegetables in Soapmaking

While you can find fruit-based essential oils suitable for cold-process soap making, such as the gorgeous 10x orange and citrusy litsea cubeba, we’re talking about actual fruit, vegetables, and some plants in this section.

The benefits of using plants in soap are different, based on what it is. Some fruit, flowers, and vegetables probably have no known benefit, while others, like carrots and pumpkin, can naturally color it. The gel inside aloe vera leaves is fantastic for creating a sensitive soap for both the face and body. Cucumber can do the same and is beneficial for those with inflamed skin.

In their whole form, fruit and vegetables will almost certainly rot in handmade soap. That’s because their mass holds on to excess water, defies the pH of soap, and can start breaking down when exposed to air.

There are ways around this though, and that’s by drying, juicing, and pureeing them. You can use juice or puree to replace some or all of the water content. With purees, a safe amount to use in soap recipes is 1 oz (28 g) of puree for every pound (454 g) of soapmaking oils. You can add it either before or after trace, and can also adjust that amount too. For example, I recommend using more in this pumpkin spice soap recipe.

If you dry and pulse the plant matter, you can add it as a fine powder. I tend to use 1-2 tsp of powder per pound of soapmaking oils. You can also make botanical teas, such as calendula or elderflower, or use the gel from inside aloe vera leaves. With aloe vera gel, treat it as you would a puree.

Another way to use botanicals in soapmaking is as decoration. If small and dry enough, it can be added directly to soap for speckles of color – this is the case when using lemon and orange zest. You can also dry the plant material and use it to decorate the tops of soap. Imagine slices of dried orange or freeze-dried berries.

Citric Acid in Soap Recipes

There are two reasons to add citric acid to handmade soap: reducing soap scum and stopping the soap from going rancid. In soapmaking, citric acid reacts with sodium hydroxide and becomes a chelator – a molecule that attracts metal ions to it. This means that if you have hard water or are using tap water to make soap, citric acid will improve the lather, extend the life of the soap, and help stop soap scum from forming. The metals and impurities in hard water and tap water cause oxidization to occur in your superfat.

Citric acid is also useful as a natural soap additive in dish soap since it helps keep dishes sparkling clean and free of soap residue. I go through how to use citric acid in my dish soap recipe, but do keep in mind that citric acid consumes lye in the soapmaking process. It creates a lye discount, and you’ll need to compensate the exact amount it uses up.

Beer and Wine in Soapmaking

If you’d like to use a rich dark red wine to make red soap, forget it. Wine turns soap tan to brown, and if you don’t use it carefully, it can end up making your bars stink a bit too. Wine does contain sugars that can help boost lather, but using sugar or honey works much better. Though wine does contain potentially health-benefiting compounds, it’s unlikely to have any effect on your skin. Better to drink a glass, in my humble opinion.

Beer, on the other hand, is an excellent natural soap additive for soap! It adds a sweet hoppy scent, a light brown color, and can boost the lather too. It may even help treat acne, eczema, and soothe irritated skin.

If you use beer or wine in your soap recipe, make sure to boil it first. Alcohol impedes the saponification process and can sometimes end in a failed batch. Carbonation, such as in beer and sparkling wine, can cause issues too. Beer and wine also contain sugars (the ingredient that boosts lather) and can heat up after you pour it into molds. Take precautions to keep the soap cool after it’s poured into the mold(s).

Scent Fixatives for Soap

If you’re using essential oil to scent soap, you will need a lot of it —generally 3% by weight. Yet, at the same time, you can’t use too much, or your soap can cause skin irritation. Soapmakers use a group of ingredients called fixatives to help prolong and amplify the scent of their soap over time. They include clay, orris root powder, benzoin resin, oatmeal, and even some essential oils.

With clay, the idea is that you pour the essential oils into it the day before you make soap. The clay absorbs it and slowly releases the scent even after its mixed into the soap. Pieces of oatmeal in soap can absorb liquid and work the same way. Anchoring essential oils with other deep or long-lasting fragrances is also used. That’s the case with musky and floral orris root powder, vanilla-scented benzoin resin, earthy frankincense gum, and woody yet pungent myrrh powder. There’s a lot of crossover between the world of perfumery and soapmaking when it comes to making scent stick!

Antioxidants in Soapmaking

If you’re making a good batch of handmade soap for the face or body, then it will have a superfat. An extra amount of oil that does not transform into soap but stays in the bar free-floating. Over time, this excess oil can and will go rancid. It’s the natural process of fatty acids reacting with oxygen and/or water and breaking down. Its characterized by yellow or brown spots appearing on soap and sometimes by a strange musty smell. Storing soap in sealed boxes does not work, as it only encourages the soap to sweat and go rancid anyway.

Using oils that are well within their best-by date is one way to combat this from happening too quickly. Storing soap in the open but out of direct sunlight is another, as is avoiding using oils that go rancid quicker than others. There’s also the addition of antioxidants such as grapefruit seed extract (GSE) and Rosemary oleoresin (ROE). They are plant-based ingredients that in the correct amount can help prolong the life of fatty acids. Please note that they are not essential oils and that essential oils do not have shelf-life stretching properties.

Sometimes you may see vitamin e in a soap recipe, with the intended purpose of prolonging the shelf-life of the soap as an antioxidant. It does not work, though. Vitamin e does not contain the correct type of tocopherol to extend the life of soap or other beauty recipes. In fact, according to Kevin Dunn, author of Scientific Soapmaking, it can do the reverse and cause soap to go off quicker.

Ingredients for Skin Therapy

There is a whole category of herbal ingredients to add to soap that may have potential skin therapy properties. Neem oil or pine tar can help with eczema and psoriasis. Aloe vera creates a gentle bar, as does cucumber. Some soapmakers also use herbs commonly used in skincare, including plantain, lavender, calendula, daisy, chamomile, and marshmallow root. They may be added as an infused oil, a tea, or a cold-water infusion.

I want to say that all of these ingredients benefit your skin in soap, but I have doubts. Even if a compound survives saponification and the pH of soap, is there enough of it to have an effect? If it can stick to your skin after you wash with soap – such as the superfatting oil – there’s potential. However, if it’s washed off after you use the soap, then that skin therapy goes straight down the drain. I’m a bigger advocate for using herbal extracts in balms, salves, lotions, and creams. Unless of course, they have another added benefit, such as calendula naturally coloring soap yellow.

Unusual Ingredients in Soapmaking

Lastly, there’s a whole list of unusual ingredients that I’ve seen people using in soapmaking. Some are used in other beauty recipes, such as pearl powder for supposed skin lightening. Then there’s colloidal silver, amber resin, snail gel, cow bile, and kombucha.

All I have to say about unusual ingredients is that just because you could add it doesn’t mean that you should. Or that it has the same effect in soap that it does in its original form and function. There’s a lot of online conjecture on what some ingredients can do. My stand is that unless it comes with some hard science backing it up, then it’s not worth my time. In some cases, it could even be unethical, harmful, or detrimental to your batch of soap.

I hope that this list of natural soap additives has been helpful. Maybe even opened your eyes to new possibilities! But before you go wild with all of these extras, remember what soap is and what its function is. It’s the natural chemical result of combining fats, lye, and water and is meant to clean. You can make it gentle and perhaps conditioning, but if you’re looking for something moisturizing, make a batch of lotion.

For much more in-depth information on making cold-process soap from scratch, check out the Lovely Greens Guide to Natural Soapmaking ✌?