Measuring hardness can be achieved using a texture analyzer. Hardness is an important characteristic of many color cosmetics, for example lip balm and lipsticks. The product needs to be in the Goldilocks region, i.e. not too hard nor too soft. Too hard, and the customer needs to work harder to apply the product, which may be the case if the air temperature is cold and the product contains beeswax. Too soft and too much product may be used, causing the customer to use too much, cause unwanted friction or feel ‘draggy’ upon application.

During a hardness study, a probe is inserted into the sample for a set distance at a set speed, which measures the force required to undertake this operation. The temperature and humidity at which testing is undertaken can be varied to allow mimicking of different climates or seasons. To have reliable results, these protocols must be very controlled and reproducible.  This is the opposite to adhesion, where the force required to remove the probe is measured. TRI has many years of experience performing these tests and can advise on the best protocols for your study.

Adhesion of a product can provide sensorial properties to a consumer, for example when comparing lip balms a highly adhesive product may feel slimy or heavy upon application, whereas a product with lower adhesion may feel like only small amounts are applied. Quantifying and benchmarking how a product behaves is therefore an important property to measure and simulating how products behave under different environmental conditions, for example how adhesion of a lipstick is affected if the surrounding environment is hot or cold, can give vital product insights.

During an adhesion test, a needle probe penetrates the sample and records the force required for removal i.e. the adhesiveness of a sample. This can be correlated to ease-of-application, for example a less adhesive product may be hard to apply but a more adhesive product may result in a heavy or sticky application experience. This is the opposite to hardness, where the force required to insert the probe is measured.