Iron sulfides are unstable under oxidizing conditions. Pyrite specimens undergo severe damage due to oxygen and humidity in museum environments. The use of fluorinated, acrylic and silicone resins as protective films for pyrite was investigated in a climatic chamber and in acid oxidizing solutions. Pyrite alteration was monitored using colorimetric parameters and measuring iron concentration in etching solutions. Acrylic resins show scarce protection in the presence of UV rays and a general tendency to yellowing. In a humid environment and in fully aqueous conditions, silicone resins do not isolate the specimen, allowing water to reach and oxidize the sample surface. Fluorinated resins are relatively the most suitable shielding films owing to their high degree of protection and the total transparency which do not change the optical characteristics of the sample. However, the tested resins do not allow an absolute insulation of the samples making ion exchange possible.