Free films are mainly used for permeation or strength and elongation testing. There are several techniques described in literature but the most common free films are prepared by the lay down technique on a substrate with a non-stick surface. Leneta polyethylene sheet or TeflonR sheet are good examples of such type of substrate.

After production, the wet films are dried for a specified time under defined conditions of temperature and humidity. After this period the film has to be separated from the support. During the process of separation the coating should not be changed in any respect (thickness, size, stressed, porosity, etc.).