One sad morning, maybe ten years or longer ago, I looked through my rigid and what did I see? It was almost completely fogged. It was as if it had frozen inside the lens. White circular spots were visible, which were glued to the lens elements on both sides of the aperture. My very experienced repairman said he wanted to try to remove the deposit, but he couldn't guarantee that it could be done completely without causing damage. It is extremely difficult to reach the inner lens elements of a rigid. He succeeded, but not without leaving traces of opening the lens. The lens is now very clear and works well, but somehow the image reproduction is no longer 100% as it was before the fog appeared.
After the cleaning:
gelatin silver print (summicron 50mm f2 rigid) leica m3
Erik.