One of the most common types of testing cosmetic formulators perform is stability testing. Unfortunately, this is not a topic covered in college, so most people who start in the cosmetic industry know very little about the subject.
Having a thorough knowledge of what stability testing is, when you need to conduct tests and how you do them is critical for anyone who wants to be a successful formulator. We will cover some key aspects of cosmetic stability testing in this article.
What is stability testing?
When putting together a cosmetic product, your primary goal as a formulator is to create a product that looks, feels, smells and performs the same way for the consumer as it did on the first day that you made it. Products that fail these standards are low-quality and may even be considered unsafe. The way you ensure a high-quality product is to conduct a stability test, which subjects your formula to different environmental conditions over a specific amount of time. You track any changes that might occur and decide whether the changes are significant.
When do you stability test formulas?
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. You’ll also find that projects change so rapidly at your company that you won’t have time to properly test many of your formulas. But there are times when you need to do stability testing. These include the following:
- New prototypes
- New raw material qualifications
- New manufacturing procedures
- New packaging
Philosophy of stability testing
Stability testing is simply an experiment in which you create a batch of your formula and put samples of it at different environmental conditions for a set period of time. These conditions vary in temperature and light levels and are meant to simulate what will happen to the product during its life cycle.
At various time intervals you evaluate your samples for various physical, chemical and performance characteristics and determine whether any changes are significant based on your company standards. If nothing changes significantly (which is your hope) then your formula is said to have “passed” stability testing. This means you can be confident that when the formula is shipped to stores and ultimately customers, it will still be as good as when it was first manufactured. It’s common in the cosmetic industry to strive for a formula that is stable at room temperature for at least one year.
One underlying assumption in stability testing is that increasing storage temperature speeds up aging reactions that might occur. An industry rule-of-thumb is that a sample stored at 45°C for 8 weeks is equivalent to one that is stored at room temperature for one year. Stability testing isn’t exact science, but it’s good enough for the purposes of cosmetic products.
How do you stability test a cosmetic?
In the US, there are no set rules on how you must conduct a stability test for cosmetic products. For cosmetic OTC products like sunscreens (EU), AP/DO, ordandruff shampoos (EU) the FDA has specific stability test requirements that you have to follow. See the FDA website for more information.
For cosmetic products, here is a basic format to follow when conducting a stability test:
- Make your batches. Sometimes a test and a control batch need to be made.
- Fill samples. Ideally, this will be in the finished packaging. Using glass jars is advisable too.
- Take initial readings. This way you’ll know where the formula started.
- Put samples at various conditions. Try temperature ranges from 4°C – 50°C. Also, vary lighting conditions.
- Evaluate samples at time intervals. Typically, 2, 4, 8 and 12 week intervals are used. Don’t forget to do a microbial challenge test.
- Determine stability. If the formula has changed little in 8 weeks at elevated temperatures, it will likely last for a year at room temperature.
Stability testing is a crucial part of creating safe and effective cosmetic products. Whenever you launch a new product or make a significant change to a current one, be sure to do a proper stability test.
Nessun commento:
Posta un commento