Читать книгу Surface Science and Adhesion in Cosmetics - Группа авторов - Страница 47

A simple lipstick containing polyethylene wax and oil was prepared by heating the mixture above 95°C until it melted completely. Then the hot mixture was poured into a lipstick mold and cooled down in a refrigerator for 20 min. The lipstick was molded and placed in a 12mm diameter bullet shape container. The lipstick was then stored at 20°C for 24 hours before measuring its hardness.

The hardness of the lipstick samples was measured using a DFGS2 dynamometer (Indelco-Chatillon). The hardness corresponds to the maximal shear force exerted by a rigid tungsten wire of diameter 250 μm, advancing at a speed of 100 mm/min.

The technique above is normally described as the “butter- cutting wire” method. The hardness value from this method is expressed in grams as the shear force required to cut a lipstick under the above conditions.