As opposed to dry skin, oily and combination skin requires less ingredients that protect it from drying out. It does, however, need more ingredients for skin control (regulation of sebum secretion). For efficient care of all skin types the use of both day and night creams is essential.
The main aim of the present diploma thesis is the development and evaluation of day and night creams for oily and combination skin whereby we want to produce cream with adequate stability and better spreadability than the creams of brand Natural cosmetics Meze that are already on the market. Based on the initial recipes of day and night creams that are already on the market, the ratio between water and oil phases per cream type (day, night) was kept, whereas the oils and emulsifiers were changed. We made seven samples of cream (including the original formulations of day and night cream) and tested them from the point of stability in order to verify their persistance, because creams are classified as physicaly unstable emulsion systems. The physical stability was evaluated with non – isothermal aging test (temperature cycling). Before performing the cyclic stability tests the rheological properties of the samples were tested, i.e. viscosity, and the samples were subjected to preliminary tests with the use of a centrifuge. The pH values of creams, which were determined before, during and after carrying out the stability tests were within the acceptable range between 4 and 6,5. No organoleptic changes were detected in any of the formulations. The viscosity of modified formulations of day and night creams increased slightly compared to the original formulations, with the exception of day cream D3 in which emulsifier was replaced. The results of spreadability test which we determined by use of an optimised method of two parellel plates, showed that the replacement of ingredients did not show the changes in their spredability. The formulations of night creams in which oil was replaced (N2 = almond oil instead of hemp oil, N3 = rose hip oil instead of jojoba oil) showed better spredability than the original formulation of night cream.With this results we achieved our goal to produce cream with better spredability, comparable viscosity and adequate stability.
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