Article by: Perry Romanowski

One of the primary tests that you will run on your cosmetic formulations is a stability test. You can read this other post for a complete procedure for stability testing.

In this post I wanted to go over the times when you should do a stability test.

1. New working prototype.

You don’t need to do stability testing on every prototype but when you get to the point of having one that gives good results, you should put up at least a minimal stability test. This would include control samples (4C and RT) and samples at accelerated temperatures of at least 45C. Early stability testing will speed up the launch process.

2. New raw material source.

Often your purchasing department will find a cheaper source of a material that you are currently buying. They’ll then want to use the ingredient right away. However, don’t use it until you have conducted a proper stability test. Just because two raw materials have the same INCI name, that doesn’t mean they are the same. When you run the cosmetic stability test, be sure to run a sample with the current formula along side the formula with the new ingredient.

3. Scaling up to production.

When your formula gets made on in production for the first time, you’ll need to do a stability test. Things don’t always work the same in production batches as in lab batches.

4. New production process.

Speaking of production, another important time to do a stability test is when you make any changes to the production process. Often the compounders will discover faster ways to make products but you’ll need to verify that the product will remain stable before implementing.

5. New packaging.

Even when you don’t change the formula, you may have to run a new stability test. The most common instance is when you change the packaging that the product is sold in. This could be a whole new package type or simply a change in the package resin source.

6. Regulatory requirements.

Sometimes you have to run a stability test just to satisfy the regulatory paperwork of a new market that your product is being sold in.

7. New production plant.

If your product is successful enough it might be produced in a different manufacturing facility. In this case you’ll need to do a stability test just to ensure that the product remains to be of the proper quality.

If you want to create consistently, high quality products, stability testing of cosmetic formulas is one of the primary tests to run.


  1. Avatar

    Thank you, Perry this is very helpful! I’m reading on stability testing and this is very concise 🙂
    I have a few questions: do you happen to know some useful literature on formulating for scaling up? And how do you test that exactly? Do you take a sample from the product first produced? Don’t you risk ruining materials if a whole batch of 5000 pieces goes wrong or proves unstable?
    Thank you in advance!

    1. Avatar

      Best advice is scale up in an affordable way.
      A protoype size batch may be a couple of kilo’s in the lab, and work well. To do stability, challenge testing etc, you’ll need to scale up to say 5Kg. That should give you some data on how things scale cheaply.
      For the big manufacturers, most* will not leap into a 5 tonne batch for the first production. They will do pilot batches of say up to 100Kg. That way if it does all go pear shaped, the overall losses are less expensive. At pilot batch I would also re-do stability.
      My advice, observe and take notes at all times once you have a product that you want to launch
      *If they are sensible. I have done this in the past, but I was a) under time pressure, b) knew the product very well, and c) B***dy Lucky!

      1. Avatar

        Thanks Duncan 🙂 I meant 5000 full sizes of 100 gr each so 50 kg will do (minimum batch for contract manufacturers). Waiting for some meetings with several manufacturers in order to see what kind of information they need, prices etc. before I make up my mind.
        I did do a 5 kg batch and it seems to hold up nice so far *knocks on wood*
        Thanks again!

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