Decay is inevitable. We can slow it, but we cannot stop it. A preservative is defined as something that protects against decomposition, yet nature dictates that everything must decompose. As we fight nature by using preservatives, we may kill off some bacteria and slow further growth, but even the more potent preservatives do not stop microbial growth.
Shelf life, more than well-being, has come to dictate a product’s ingredients. A skin-care product is expected to weather all sorts of contingencies. It may sit in inventory for a few months. It may travel and then sit in someone else’s inventory. It may sit on the shelf in a store for six months, and the consumer may not open it for three more months. Manufacturers demand years of stability from these products, and add enough synthetic preservative to ensure a long shelf life. But research has shown that the bacteria continue to grow, it’s just that the more potent chemical preservatives, colors, and fragrances camouflage the decay. We don’t benefit from true purity, yet we suffer the effects of indiscriminating toxins.
As soapmakers, we can control what goes into our soaps. We can choose to use no preservative and allow our soap its fullest potential — and limitation. We can use natural preservatives which add nutrients to the soap while gently discouraging spoilage. Here too, we must accept eventual decay, but still offer a superior product.
SYNTHETIC PRESERVATIVES TO AVOID
Formaldehyde (in the form of MDM Hydantoin)
Imidazolidinyl urea (known as Germall)
Phenoxyethanol (phenol and phenolic compounds)
Captan
Boric Acid
Hydroquinone
Triclocarban
Irgasan DP 300
Alkyltrimethyl ammonium bromide
BHT (butylated hydroxytoluene)
BHA (butylated hydroxyanisole)
Calcium Disodium EDTA
DHA (Dehydroacetic Acid)
TBHQ
Alternatively, we may choose synthetic preservatives, which may offer the longest protection of all but with a great price. The list of known carcinogenic preservatives is growing. Our skin, which so readily absorbs borage oil, also absorbs toxins. A preservative strong enough to kill some bacteria will also kill our skin’s beneficial bacteria. Finally, the active nutrients so carefully chosen for their ability to interact with cells, tissue, and the environment are rendered less effective, if not inert, in the presence of the more potent synthetic preservatives. The choice is ours.
Though I provide a list of synthetic preservatives to definitely avoid, I discourage the use of all synthetic preservatives, and therefore do not offer instructions for their use. All of my research has discouraged me from experimenting much with synthetic preservatives, so I’m not comfortable making recommendations about any of them.
Since the ideal preservative does not exist, I choose natural preservatives knowing their limitations and expecting only what is reasonable. They extend the shelf life of the soap by a few months, without altering the other ingredients and without causing allergic reactions. They also offer skin-care qualities.
People are eager to be educated about natural products and their strengths and limitations. You will be pleasantly surprised to see how receptive others are to relearning what to expect from their skin-care products. Once people understand what makes a natural product more pure and safe, they are willing to accommodate its peculiarities. They learn to purchase smaller quantities and use up the product before buying more. Should a bar spoil (which is not common), they accept occasional throw-aways as the price for purity and safety.
Cold-process soaps are more vulnerable to spoilage than soaps made by other methods because they are normally super-fatted (made with excess oils) for mildness. Toward the end of the saponification process, the lye is used up before all of the oil, leaving some oil out of solution in the final bars. This free fat is moisturizing and soothing, but it also causes deterioration. In solution, oils are more stable.
Free oils and nutrients like aloe vera and honey are active ingredients, beneficial because they have living properties in the final bars of soap. As these ingredients complete their life cycles, decay is inevitable, a fact we must understand and appreciate.
A soapmaker selects a preservative for its antioxidant and antimicrobial properties. When oxygen molecules are able to break their bonds and travel freely throughout an oil or a fat, they combine with other molecules, thus altering the structure of the soap. This is oxidation, the first step toward spoilage, discoloration, and a decrease in nutritive value. As oxidation takes place, soaps will show visible signs of spoilage; small, yellowish circles will appear, just one at first, with more appearing on the soap’s surface over a number of weeks. An off-odor follows the first circle of rancidity.
Antioxidants greatly reduce this process by pairing with the “loose” oxygen molecules, rendering them less destructive, and therefore prolonging the useful life of our soap. Antimicrobial preservatives slow down the growth of bacteria in soap, but they cannot prevent it.
There isn’t a rigid formula for determining which natural preservatives and how much of each to add to your soap; many factors influence their effectiveness. You need to experiment to determine what works best within your own particular soap-making formula.
The most helpful book I’ve read on this subject is Natural Organic Hair and Skin Care, by Aubrey Hampton, an authority on natural, organic cosmetics, and founder of Aubrey Organics. Over the years, he and other researchers have tested a variety of natural preservatives, including pure essential oils, citrus seed extracts and oils, vitamins, tocopherols, and carrot root oil. His results are exciting and compelling. I now include a combination of a few of these nutrients in my soaps, and the shelf life has been extended by months. My average bar is now good for a year. Longer than a year is more than we should expect from a natural product.
A few observations: Citrus oils are prone to rancidity; ascorbic acid, water-soluble vitamin C, is nearly impossible to find in a non-synthetic form, and it also overreacts to the sodium hydroxide within the lye solution, turning the lye dark and unpleasant; the oil-soluble form of vitamin C, ascorbyl palmitate, which can be incorporated into the fats and oils, is always synthetic; and retinol, naturally derived vitamin A, has practically been replaced with a synthetic version. The natural form of retinol is occasionally available, but the cost is prohibitive.
WHAT CAUSES RANCIDITY IN SOAP?
Rancidity is related to many other factors. Unsaturated oils and fats are usually more prone to rancidity. A mild soap, using the minimal amount of sodium hydroxide for a not quite complete saponification, will have excess fats or oils which do not saponify. These superfatted soaps are gentle and mild, but they also spoil more quickly. Soaps and raw soapmaking materials which are exposed to heat or light will spoil sooner. High percentages of synthetic fragrance can also affect a soap’s stability. A humid environment accelerates deterioration.
Grapefruit seed extract and carrot root oil used in combination offer vitamins A and C and skin-care qualities in a non-synthetic form. If your formula is vulnerable, look toward a combination of grapefruit seed extract, tocopherols (vitamin E), and carrot root oil. These are the three natural preservatives I prefer.
Some of these preservatives are added to the oil phase (the mixture of oils and melted fats) of your soap and some to the water phase (the combined and cooled mixture of sodium hydroxide and water). Some are antioxidants, while others discourage bacterial growth. A carefully designed combination can offer your soaps a broader protection from rancidity.
GRAPEFRUIT SEED EXTRACT
Nature: This is a by-product of the citrus industry and is my most reliable antioxidant for soapmaking. Made from vegetable sources, grapefruit seed extract contains vitamin C (ascorbic acid) and glycerin. It has a seven- to nine-year shelf life.
Use/Benefits: Along with its antioxidant properties, grapefruit seed extract is also antibacterial, antimicrobial, deodorizing, astringent, and antiseptic.
Quantity/Procedure: Add between 0.5 and 5 percent (of the total soapmaking ingredients) grapefruit seed extract to the oil phase before adding the lye solution. Note that the grapefruit seed extract would precipitate out of the lye phase — I learned this first hand.
TOCOPHEROLS
Nature: These are naturally derived forms of vitamin E, existing as either alpha-tocopherol, beta-tocopherol, gamma-tocopherol, or delta-tocopherol. The gamma- and delta-tocopherols are known for their antioxidant properties.
Use/Benefits: Tocopherols can delay rancidity within certain soap formulas, and they secondarily offer healing properties, thereby softening dry skin. Avoid dl-alpha-tocopherol, the synthetic version of vitamin E.
The addition of tocopherols is most effective in preserving tallow and lard, which are low or deficient in natural tocopherols. They also help to protect the more vulnerable essential oils like lemon, orange, and grapefruit. Vegetable oils already have varying percentages of tocopherols, so additional tocopherols may add only a small benefit. Quantity/Procedure: When using them in all-vegetable soaps, combine the tocopherols with grapefruit seed extract for greater protection. Be sure to use natural tocopherols, not the synthetic reproduction. Add 0.06 percent (of the total soapmaking ingredients) to the oil phase before adding the lye solution.
CARROT ROOT OIL
Use/Benefits: Like grapefruit seed extract, carrot root oil is an excellent substitute for the pure forms of vitamins C and A, which are becoming more and more difficult to buy in their natural states. Carrot root oil is an antioxidant, high in vitamin A, vitamin E, and provitamin A. This oil is especially good for dry, chapped skin, as it accelerates the formation of new cells.
Quantity/Procedure: Add 0.5 to 5 percent (of the total soap-making ingredients) carrot root oil to the oil phase before adding the lye solution. Combine with other natural preservatives for greater protection.
