When a self-adhesive film isn't flat, the reason is to be found in the humidity of the room being too high or to the contrary to a environment that is too dry: the quantity of water present in de room has enourm influence on the siliconed paper that for it's nature tends to absorb or release the water present in the fibres. To solve this problem it is advised to keep the film in rooms with temperature and humidity as stable as possible, and to let it get used to the conditions of the new room for at least 24 hours. It is important the keep the film in the polythene bag: it signifies protect it not only from dust but also from brusk temperature-changes.