The lampshades never an easy to clean because it is a delicate material. Those made in the parchment are elegant, but very delicate and require special cleaning. A small hand vacuum dust removed them without any harm to their texture.
To keep them flexible and prevent the parchment from drying out and to break down, a cloth dampened with water and liquid wax is the solution.
If soil has been ideally strong detergent and a few drops of ammonia.