Every soap maker has experienced the following scenario- You just created a beautiful hot process soap, maybe using the UG2HP 10-Minute Cocoa Butter Dream recipe, and scented it with a lovely Vanilla Cream or maybe a Vanilla Hazelnut Latte fragrance. After you cut your loaf and set it aside to cure, you notice something strange start to happen. Your creamy white soap begins to discolor and eventually morphs from a bright white to a dark, muddy brown color.
What happened to this soap? Vanilla happened! Many fragrances rely on vanilla to provide that sweet, warm and milky aroma that we crave and desire. Vanilla is added to many different fragrances, and although we may love them, fragrance oils that contain vanilla will cause discoloration, ranging from light tan to dark brown. The higher the concentration of vanilla in the fragrance, the more discoloration.
So, what causes this discoloration? The perpetrator is a chemical called vanillin. Vanillin, also called methyl vanillin or 4-hydroxy-3-methoxybenzaldehyde, is an organic compound with the molecular formula C8H8O3. Its functional groups include aldehyde, ether, and phenol. It is the primary component of the extract of the vanilla bean. This chemical compound is naturally present in vanilla beans (obviously), coffee, wine, smoked meat, and even fruits like strawberries and blueberries. It is an aromatic aldehyde that provides the sweet, warm and milky vanilla scent that is included in so many of our favorite fragrances. Although vanilla is a chemical compound found in nature, it is often synthesized in the lab from ingredients like cloves, cinnamon, and wood pulp to meet the high demand due to its popularity.
When vanilla oxidizes, it begins to turn brown. Oxidation, as you may recall from our article about Polyunsaturated Fats & Rancidity in Soap, is caused by the loss of electrons during a reaction with an oxidative molecule, atom or ion. Light, heat, water, and exposure to air increase the reaction rate of oxidation, all which are part of the normal hot process soap making procedure. This discoloration doesn’t just happen in soap, it also happens in other products that include fragrances that are comprised of vanillin, including lotions, shampoos, and bath bombs. Vanilla has a pH of around 4.3 and when combined with products with an alkaline pH, like our hot process soaps, the discoloration and browning intensifies. In hot process soap making, compared to cold process, the discoloration may happen within minutes if the vanillin content is high enough because of the increased temperatures. Discoloration in your soap may appear within the first hour, or may take days, even weeks to appear. Often vanillin soaps will first appear brown only on the outside of the soap, but as the oxidation process progresses, the center will also discolor, and the soap will become uniform and brown in color.
Our Vanilla Cream and Vanilla Hazelnut examples from above, make it easy to identify the vanilla content because “Vanilla” is included in the fragrance name. Unfortunately, many fragrances that contain vanillin are harder to identify. For example, fragrances like Key Lime Pie and Coconut Caribbean will contain vanillin, even though it’s not listed in the fragrance name. Because of this, it is always important to check the fragrance information before purchasing the product, even if you don’t suspect that it will contain vanillin.
Many fragrances will have a 1-2% vanillin concentration that may or may not be noticeable when you smell the fragrance, but it will be listed in the fragrance information. Reputable suppliers will provide information about the vanillin content to customers so that they can make informed decisions. A good rule of thumb is to double check any fragrance that has a sweet and warm aroma. These types of fragrances have an increased likelihood of containing vanilla. Fragrances from these categories often contain vanilla: baked goods, honey, oatmeal, milks, almonds & other nutty fragrances, spices, coffee, coconut, amber, musk, woodsy smells, tobacco, and more.
Combating Discoloration
If vanilla fragrances are so popular, how can we combat this problem? There are several steps that can be taken to reduce the risk of discoloration due to the vanillin content found in many of our favorite fragrances. Let’s explore some of these options below.
Embrace the Brown
Because many of the fragrances that contain vanillin are commonly associated with brown colors, you can design your soap with the knowledge and intention that it will discolor. For example, you can make our famous Vanilla Hazelnut Coffee soap with the understanding that it will brown due to the fragrance. By allowing the soap to discolor, it will create a beautiful, deep brown soap.
Partial Fragrance
You can use your knowledge of the effects that vanillin has by intentionally fragrancing only a portion of your soap with vanillin. You know that soap that contains vanillin will discolor, but soap that does not contain vanillin won’t. This can have the same design effect as using a brown colorant. We like to create our subtlety fragranced Honey & Oatmeal soap by splitting the recipe into two equal parts. Half of the soap is fragranced with a Honey & Oatmeal, a fragrance that contains vanillin, and the other half is left unfragranced. When both portions are swirled together, it creates a beautiful white and brown design.
Titanium Dioxide You can create a lighter shade of brown by adding titanium dioxide. Instead of creating a deep brown due to vanillin oxidation if left uncolored, the addition of titanium dioxide will create a lighter shade of brown. The more titanium dioxide that is used, the lighter the shade of brown. You can create different shades of brown in the same soap, by coloring different portions with incremental amounts of titanium dioxide.
Antioxidant
We know that the discoloration of vanillin is caused by oxidation, so adding an antioxidant can help slow this process down. Popular antioxidants include vitamin E, Rosemary Oleoresin Extract (ROE), or a combination of butylated hydroxytoluene (BHT) and sodium citrate (one of the most effective antioxidant-chelator combinations). Antioxidants are not permanent solutions, and if the vanillin content is more than 1%, this may not be an effective option.
Vanilla Stabilizer
I saved one of the most popular and widely used options for last- the vanilla color stabilizer. A vanilla stabilizer is used to prevent the discoloration caused by the vanillin and can be your best friend when creating lightly colored vanillin soaps. Vanilla stabilizers are purchased in a liquid form from cosmetic and soap suppliers. The stabilizer and fragrance oil are combined first and then added to the soap together. The suggested usage rates are 1 part vanilla stabilizer to 2 parts fragrance for fragrances that contain less than 10% vanillin and 1 part vanilla stabilizer to 1 part fragrance for fragrances that contain more than 10% vanillin.
Although a vanilla stabilizer may prevent discoloration temporarily, many soaps made with fragrances that contain a higher concentration of vanillin will eventually discolor over time. This process may take a few weeks, a few months, or it may take years. We used “Vanilla Cupcake” fragrance that contained 11% vanillin for our Vanilla Confetti Soaps below with a color stabilizer and it has remained bright white for over 6 months now, with only a very minor amount of discoloration, only noticeable to us.
The TRUTH About Vanilla Stabilizer
If you take a look at Wholesale Supplies Plus website at their vanilla stabilizer, it says that the INCI (International Nomenclature of Cosmetic Ingredients) name is “Fragrance”. When I asked Brambleberry what to include on my soap label, I received the same response, “fragrance.” Rusticescentuals, CandleScience, Aztec, and Great Candle all state that a vanilla color stabilizer is a “fragrance.”
I teach all of my UG2HP students to make an informed decision about their recipes. I want students to be able to answer questions about additives not only for their customers but also for themselves. If the vanilla stabilizer that we purchase from suppliers is odorless, doesn’t it seem odd that it is considered a “fragrance” by every soap supplier out there?
If you take the time to learn about the science of each of your additives, like we are in this article, you will quickly realize that vanilla stabilizer doesn't really seem like a “fragrance” or "parfum." In fact, I actually despise that this is allowed. According to INCI 21 CFR 701.3(a), “The label on each package of a cosmetic shall bear a declaration of the name of each ingredient in descending order of predominance, except that fragrance or flavor may be listed as fragrance or flavor.”
Yep, somehow this is perfectly acceptable and legal to list vanilla stabilizer as a fragrance on labels, even if it does not actually add any fragrance. Most soap making suppliers won't provide the actual ingredients in order to protect their "proprietary fragrance blend", but again, where is the fragrance then? Although some suppliers will add 1-2% fragrance to the vanilla stabilizer solution, and it is technically combined with a fragrance before use in soap and other cosmetics, I still think that soap makers and consumers should be provided with the actual ingredient information and allowed to make their own conclusions about the use (or not use) of products based on their ingredients. Even though we have come quite a long way in consumer protection and transparency, there is still some room for improvement!
So, what exactly is vanilla stabilizer? One of the most commonly used vanilla stabilizers is a chemical called sodium thiosulphate (or sodium hyposulphate). Other popular vanilla stabilizers include disulfurous acid disodium salt, which is the primary component of Crafter's Choice CP, and sodium bisulfate. Notice something similar about their chemical compositions?
The chemical formula for sodium thiosulphate is Na2S2O3 and it exists as a colorless water-soluble crystalline compound. It has many uses, including stain removal, leather tanning, bleaching, photographic processing, and even aquarium care. Sodium thiosulphate also has some incredible medical uses and is used in the treatment of arsenic, lead, mercury, and bismuth poisoning, in addition to treating rare conditions caused by toxicity. It is also used as a preservative in many food products. To soap makers, sodium thiosulphate/hyposulphate plays an important role in the prevention of discoloration and browning due to the vanillin found in many popular fragrances. Sodium thiosulphate is one of the most common vanilla stabilizers used in many commercial MP bases sold and used by major companies like Brambleberry and Stephensons.
DIY Budget Vanilla Stabilizer
Now that you know a little bit more about what is actually in most vanilla stabilizers, you can create your own. First, we need to hydrate the crystals to create an aqueous solution that can be easily mixed with our fragrance. To create your own vanilla stabilizer solution, create a 25% sodium thiosulphate solution by combining 25% sodium thiosulphate with 75% distilled water. Next, add the solution directly to your soap or add to your fragrance oil (not oil-soluble but will help remember to add it and will mix in the soap). The usage rates are the same as commercial stabilizers. There may be a slight chemical smell, although this will dissipate upon use. You can create the exact amount of vanilla stabilizer solution needed for just one batch, or you can create a larger concentration and bottle it for later use. If you would like, you can even add an antioxidant like vitamin E oil to the dissolved solution.
Sodium thiosulphate and other common vanilla stabilizers are very inexpensive to buy. Sodium thiosulphate can be purchased online for as little as $0.20/oz. That means that you can create a solution of 4 ounces of fragrance stabilizer for only $0.20. That is only $0.05 per ounce of vanilla stabilizer! That is much more affordable than other fragrance supply companies! Wholesale Supplies Plus sells their 4-ounce fragrance stabilizer for $15.99 (with a $5.99 handling fee and $6.99 shipping fee if not over $25), Nature’s Garden sells 4 ounces for $7.99 plus $8.99 shipping, and Great Candle sells their 4-ounce bottle for $25.97. No wonder why they don’t want to list the ingredients! There is a HUGE profit to be made in vanilla stabilizer!
(When used in cold process soap making, like may stabilizers it may cause an accelerated trace and this should be noted.) Stabilizer Limitations
It should be noted that there are limitations to vanilla stabilizers. Vanilla stabilizers will only prevent discoloration from vanillin and will not prevent discoloration from any other additives or causes. Vanilla stabilizers are not compatible with all fragrances due to the other components of the fragrance oil or other recipe additives which may render it ineffective. And last, vanilla stabilizers don't always provide the necessary protection against discoloration and oxidation and will only slow the rate of oxidation, not prevent it. A sufficient amount of stabilizer must be used and even then, oxidation will often still occur and many soaps will discolor over time, especially those with higher vanillin concentrations.
With all new ingredients, it is always best to test a small sample before committing to a larger, more expensive batch. We highly recommend that you test your stabilizer in different coconcentrations until you have found your preferred amount.
Conclusion
By using the tools provided by The Ultimate Guide to Hot Process Soap, you are able to make informed decisions about your recipe and your design process. You can use the information from this article to prepare for and address the discoloration caused by the oxidation of vanillin. You can also create a budget vanilla stabilizer and protect your soaps from browning, without spending a fortune!
Happy Soaping!
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