With the Speed of Light: A Look at Accelerated Testing

Posted: October 9, 2007

Whereas most people know that scientists like Copernicus unveiled that the world is spinning at a constant speed— a logical consequence of placing the sun at the center of the universe— most feel that the world is turning at an ever increasing speed. Almost 20 years ago, people sent contracts by mail and subsequently waited a few days if not weeks until the other party had received, read, signed and returned them. Nowadays, we take a former contract, change a few words, print it off, sign it, scan it in, attach it to an e-mail, enter an e-mail address and hit the send button. And often, it is annoying if a response is not received within a few hours.

Increasing the speed of something is a relative thing. In times gone by, on August 12, 490 BC to be precise, a messenger was sent out from Marathon to Athens to inform the Athenians that the Persians were coming. Pheidippides ran the 42 km distance without stopping. He would have been subjected to temperatures as high as 39 °C, and just after he arrived in Athens with the news, he died most likely from heat stroke.

The world wants instantaneous responses. When things can go faster, it is hard to accept a slower than maximum speed. Comsumers in the personal care industry often face a temporary benefit, but when that benefit becomes standard, they want more, i.e. darker skin tan, less skin tone, faster delivery, leaner thighs, longer legs or holidays, etc., etc. Where is this list of superlatives leading you...to my topic—accelerated testing.

We test a number of things in our cosmetic industry. We test for safety, actually, the in vitro alternatives will discuss next time have a much greater chance of being accepted if they also offer a speed benefit; for stability; for efficacy; for microbiological contamination; and for interactions between the (ingredients of the) product and its container. Physical stability testing specifically can be quite time-consuming. Imagine you had to store all your samples for three years before you were able to state that your product was stable for this period of time. This would be far too long relative to the lifetime of the product in the market place.

Our world would have moved on. We, therefore, invented accelerated testing to gain time. Take physical stability testing of formulations as an example. Emulsions may undergo flocculation (internal droplets form a weak, reversible association without a change in size), coalescence (merging of internal phase droplet to form one larger particle – but of different sizes), Oswald ripening (the newly formed larger droplets are uniform in size), creaming or sedimentation (less dense particles rise to the top), or phase inversion.