Usually, there are 12 samples split into two groups (6 for room temperature/6 for an incubator). Many more samples are required in the case of foil sachets, i.e. aluminium foil tests – at least 20. If additional tests are carried out, an adequate number of samples is needed. Guidelines: 1. Before a compatibility test, both packaging and the product should be tested when it comes to their correctness. 2. If it is possible, packaging should be fi lled and labelled on the packing line, if a product is to have labels. If not, it is possible to fi ll the packaging manually. 3. Products should be divided into 2 groups and marked correctly: a. samples designed for a temperature-induced accelerated aging test: - samples (a cosmetic product + its packaging) are kept in an incubator depending on the kind of cosmetic products in the temperature of 37˚C or 45˚C, b. samples are kept in room temperature (control samples), c. samples are kept in room temperature left to be controlled after 3 years.