Heat sealing films provide very good protection against evaporation and contamination due to the tight seal. Aluminum foils are used for PP and PS plates. They are resistant to solvents and are used both at low temperatures and for storage at room temperature. Depending on the application, they are peelable or pierceable. The transparent film in PE is used for PP sheets. Due to its good optical properties it is suitable for qPCR and colorimetric assays.