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The Importance of Stability Testing your products before your product launch.


So you have a great idea for a product and you want to sell it to the public! There is a process to this that should be followed before you sell it to your customers. 3 very important tests that need to be run are:

  1. Microbial tests to assure your product will stand up under various conditions such as introduction of bacteria (such as inserting a finger into the product) .
  2. Packaging tests to make sure your product is suitable for the packing you have selected.
  3. Stability tests to assure it will stand up under various conditions such as shipping, or heat and light. For example if your product is sitting in a window and the sun is shining in, it could get heated up quite quickly. Under these conditions your product could separate, the growth rate of fungus or bacteria is increased,  your product could discolor. Most Hand Crafters do not have a background in cosmetic science nor can they afford pricey testing so know how to conduct these tests at home is important. For most tried and true formulas with traditional ingredients this is not an issue. Once you start adding active ingredients, herbal tincture and so on, it gets trickier.

Many Hand Crafted products contain a concoction of natural and traditional cosmetic ingredients that possibly have never been combined before. Both are chemicals which can easily react with each other to form chemical reactions that might not be anticipated. A perfect example  of this would be a bath bomb. The mixture of the alkaline baking soda plus the acidic citric acid on it’s own it stable. As soon as you add water your have created a chemical reaction that causes gas bubbles.

Hand Crafters owe it to their customers to ensure they are protecting them in every way they can and also to themselves to assure they are not increasing their companies liability by not properly taking time to run all the necessary tests and researching all the FDA Guidelines.

The article I am sharing was written by Perry Romanowski at the Chemists Corner to give you an idea as to how you can go about testing your product before launching it on the market.

Article by: Perry Romanowski

Here’s the biggest difference between what you experienced in your college organic chemistry lab versus a cosmetic formulation lab. In an organic lab, you mix chemicals together and hope something happens. Ideally, you get a chemical reaction you expect. As a formulating chemist, you mix chemicals together and hope nothing happens. Cosmetics are mixtures of chemicals that mostly aren’t supposed to react with each other.

Unfortunately, they often do react (or otherwise change) so you need to test your formulas to see how long they will last. This is called Stability Testing and is something a cosmetic scientist spend much of her time doing. In this post, we’ll give a brief description of the test and suggest when, why and how it should be done.

What is 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 select intervals you evaluate your samples for various physical, chemical and performance characteristics to see how they have changed. If the changes are minimal according to your company standards, then your formula is said to have “passed” stability testing. This means you can have confident that when the formula is shipped to stores and ultimately customers, it will still be as good as when it was first manufactured.

The underlying assumption in stability testing is that increasing storage temperature speeds up any aging reactions that will occur. A handy rule of thumb is that a sample stored at 45C for 8 weeks is equivalent to one that is stored at room temperature for one year. This isn’t an exact predictor, but is good enough for the purposes of cosmetic products.

A sample stored at 45C for 8 weeks is equivalent to one stored at room temperature for a year

When do you perform stability testing?

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 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.

1. New prototypes — Whenever you make a new formula and are satisfied with the way it performs, you’ll want to do a stability test to ensure that it will stay together. Don’t bother testing all your prototypes, just the ones that work the way you want.

2. New raw materials — Whenever you have to change the fragrance, color, or other raw material in a formula, you’ll have to do a stability test to make sure there aren’t unacceptable changes. Also, when you have a new raw material source (or supplier) you’ll want to run a test.

3. New manufacturing procedure — Manufacturing is always trying to find faster ways to make formulas. This often means they change some order of addition or shorten mixing time. Whenever changes like these happen, it could affect your formula. Run a stability test to see if the change is acceptable.

4. New packaging — Cosmetic products change their look almost yearly so packaging is constantly being modified. Whenever you get a new package, you’ll have to determine if the formula continues to be compatible. Stability testing helps ensure that it is.

How do you stability test a cosmetic?

There are no set rules on how you must conduct a stability test for cosmetic products. Of course, for cosmetic OTC products like sunscreens, AP/DO, or dandruff shampoos the FDA has specific stability test requirements that you have to follow. See the FDA website for more information.

Here is a basic format you can follow for conducting a cosmetic formula stability test.

Step 1 — Make your batch. Calculate how much to make based on the number of samples you’ll be using for the test. It’s a good idea to make 30-40% more than you think you’ll need.

Step 2 — Fill your samples. Ideally, you’ll have the correct packaging but don’t count on it. When appropriate, fill glass jars with the product along with the finished package. In stability testing, you want to do both glass and packaging if possible. The number of samples depends on how much testing your doing but at minimum you should have 2 samples for each storage condition.

Step 3 — Take initial readings. Once you have a sample filled test it for all the characteristics you’re going to evaluate later. The exact tests depend on the product but minimally you’ll want to record notes about the appearance, color and fragrance. You’ll also want to take pH and viscosity readings. For aerosol products you will test spray patterns.

Step 4 — Put samples at different conditions. Stability testing requires different temperature and light conditions. Some standard temperatures include 50C, 45C, 37C, 25C (RT), and 4C. You’ll also want to conduct a freeze/thaw stability test which involves cycling your product through 24 hours of freezing then 24 hours of thawing. Different lighting conditions involve a fluorescent light box and a natural light box (to simulate sunlight).

Step 5 — Evaluate the product. Samples should be evaluated at the following intervals. 2 weeks, 4 weeks, 8 weeks, 12 weeks, and 52 weeks. Only the RT, 37C and 4C samples will be evaluated after one year. The highest temperature samples and the light exposed samples only need to be evaluated for the first three test intervals. The evaluation tests should be the same ones you conducted when taking your initial readings.

Step 6 — Determine stability. After 8 weeks you can confidently decide whether your formula is stable or not. Nearly all products will exhibit some change so it will be up to you (and your boss) to decide whether the product passed or not.

Early in your career, stability testing will be one of the most common activities you’ll do. If you can create a system that you consistently follow, you’ll avoid burn-out and be able to confidently communicate when a product is appropriate to launch.

How does this compare to your company’s stability procedure? Leave a comment and let the rest of the cosmetic chemists here know.


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