Wet collections are rich in information to study the evolution of species or ancient pathologies. However, they are sometimes neglected, poorly documented and difficult to preserve. To keep these archives for future generations, we have inventoried in detail the degradations observed in the collections and undertaken research on the hermeticity of the jars. To top up the jars appropriately, the fluids is first identified without opening the jar and the impact of a change of fluid from the macroscopic to the microscopic scale was studied. The results of this research are