How To Stability Test a Cosmetic Formula
The biggest difference between what you experienced in your DIY kitchen versus a college organic chemistry lab is KNOWLEDGE. In an organic lab, you mix chemicals together and hope something magical happens. Your mixture A mixes with your Mixture B. And if you’re lucky you get the formula you had expected. As a formulator, you mix chemicals together and hope nothing disastrous happens. Cosmetics are mixtures of complex chemicals that mostly don’t play well together.
Unfortunately, many things that we mix more often than not don’t react together and the results are not quite what you hoped for. This is why testing is so important. So you need to test your formulas to see how long it will last. Ask yourself what conditions made the product last and can you continuously create this environment. This is called Stability Testing. Stability is something that we must spend many man hours doing to not only perfect our formulas, but to make sure the product is stable
Why stability testing?
All cosmetic scientists, chemists,formulators and DIYers must prove their product stable before it can be massed produced or be given to someone for purchase. Stability testing is proof that you have done due diligence to make sure your product remains stabilized over various conditions. Remember your product will be potentially shipped across different times zones, temperature and environments.
How to Perform Stability Testing
First you create a master batch of your formula. Put samples of your formula in different environmental conditions for a set period of time. I like to do 6 month and 12 months testing. Yes, I know that seems extreme, but what happens if your product does not sell quickly? Your customers would not like to invest in products that have a short shelf life. Test your product in conditions that vary in temperature and light; especially if your products have fragrance and oils in it. Fragrances and oils can make or break your product. Most products with fragrances and essential oils must be protected from light to delay breaking down. What you are doing with stability testing is simulating an environment in which your product will be stored.
Create an Excel spreadsheet that allows you to track data periodically. For example, Sample A you may want to note texture, smell and stability at 1 week intervals. I would suggest at first to do biweekly intervals at least the first two months and then monthly after that. At select intervals you evaluate your samples for various physical, chemical and performance characteristics to see how they have changed. If the changes have occurred go back and look at what you can change. For example if the fragrance has disappeared in the formula. Consider adding a little more fragrance to the maximum load. You may need to add only essential oils. But, these two have shelf lives. So there are many factors to consider before you truly launch a product. Repeat every necessary step until you are happy with your product. If there are variations, you might consider a warning label or an expiration date. The bottom line is this, you must make a safe product and this critical step cannot be overlooked.
Oxidation is the biggest enemy to product stability. As the product is exposed to air, the more the product ages or degrades. Take the necessary steps in the beginning. You might want to choose air sealed containers, light protected jar or bottles. Invest in the right stuff in the beginning and you will not have to go back to the drawing board as often. A sample stored at 45C for 8 weeks is equivalent to one stored at room temperature for a year. This isn’t exact science, but it is a great starting point. Since you’ll be making hundreds or thousands of prototypes during your career, it won’t be practical to run a stability test on all of them. Sometimes your products are so spontaneous or they become a big hit in the testing phase and you need to get the product out sooner than expected. Are you free to give up on stability testing? Absolutely not! Find time, even after you’ve formulated a product and do the product testing. If there are ever any potential lawsuits, you have done your due diligence by testing.
You’ll also find that changes happen so rapidly at your company, you won’t have time to properly test many of your formulas. But there are times when you need to do stability testing. Here is a short list of some of the most important times to conduct a stability test. Also, remember that everything that you make will not be successful. Disappointing, I know. But, most people are lucky to have one major product that they develop that is the best seller. The great thing about having one product is not just manageability, but one great product can be changed with the increase of a few additional ingredients or just changing fragrances, container design or making the product multi-functional. Think about for a moment, there are many companies that sell only one product. However, they have managed to make that one product appeal to different consumers. The best example of this is soap. You may not have ever thought about this, but liquid soap is one them. For example, you have liquid dish soap, liquid laundry detergent, liquid hand soap and body wash. These products are essentially the same thing with slight variations, yet we’ve found many different uses for these products to sell to consumers. Now tell me, have you ever considered just buying a large order of liquid soap and using it throughout your house? Probably not. Of course, not because you thought you needed a different soap for dishes, a different soap for your hands, a different soap for laundry and a different soap for the body. I want even get into shampoo. Same product, but the advertisers deceived you.
I test, whenever; I have a totally new product. So all my new prototypes get stability testing. If am using new raw materials that I don’t have a working knowledge of then I test, test, test. I won’t have no clue how this product works over time if I don’t do the leg work now. In my early days, I have had several products that failed after adding some new great herb, fragrance or raw ingredient that has become popular. These days now, I pretty much stick with the known and proven staple ingredients. I have a documented history on this and I can build from these products.
One thing that I must pause to mention here is that there will come times when you have purchased ingredients that you have used time and time again and yet, your product is not stabilizing. The problem may not be you, the problem make be with the manufacturer. This is a big problem for me when I am working with pure organic materials. If something is truly organic it is not the same every time. This is the fight that I have with many organizations. In my case I use 100% pure, unrefined, Grade A Shea Butter. However, the texture and consistency is never the same all the time. I combat this by adding a disclaimer to my website or placing it on my packaging. I have found that this helps me more than hurt me. My customers love the transparency.
Happy Stability Testing!