Update: cleaned 40 years of haze off a Rolleiflex viewing screen and the finder popped
A customer brought in his dad's Rolleiflex 3.5F from a garage in Dayton, and the focusing screen looked like frosted glass when I got it on the bench. Two rounds with diluted dish soap, a soft brush, and a rinse in distilled water cleared off the old nicotine film, and the difference under a lamp was night and day. I could actually snap the split image together on a mailbox across the street instead of guessing. Has anyone here had luck with the same soak method on a Hasselblad screen, or do those coatings not handle it?