Writing and erasing a holographic image on a PTD (photothermoplastic device) needs the adjustment of a great number of parameters. Only the parameters concerning corona charging are discussed. In conditions described previously, the diffraction efficiency of holograms recorded on a PTD reaches 20%. Such a high value makes PTDS interesting for many applications. However, the main interest in PTDS comes from the possibility of cycling, i.e. erasing and writing new holograms. In optical switching for telecommunication networks, many cycles are needed. With thermoplastics, such as SE 10, an abietic ester which gives high diffraction efficiency, several hundred cycles are made. The corona charging conditions are studied. It is shown that it is useful to choose a good-quality needle (materials, radius of curvature) because its degradation can be observed. This needle quality is discussed. It appears also, that in a corona set-up when an organic product is layered on the counter plate, the corona current can be abnormally high; it can be three or four times higher when a resistive organic material is layered on the metallic conductive counter plate than when it is not. This widely spread phenomenon is discussed. Finally, the acceptance potential that varies with corona conditions and which is a material parameter that varies with sample nature, temperature or layer thickness is presented. Also, the decrease of surface potential with time is shown to be a specific property of each product.