Originally posted by gofour3 I checked a LX brochure I have and it mentions the focusing screen coating:
"Each screen is specially treated with a newly created Pentax coating which enhances light transmission and ensures the brightest possible viewfinder image."
So it looks like this unique "Pentax coating" is what's getting messed up with IPA.
Phil.
Interesting, so the info I found on the MIR page mentioned in my post #11 is correct.
However, @Astro-Baby sees the same effect on screens from other brands. We humans tend to think in OR functions, but it could well be a combination of factors. What we have learned though is that using IPA on a focusing screen is not recommended.
I still think an ultrasonic bath with a suitable solvent might be worth trying out. A model with adjustable power, temperature and time. Perhaps with a cleaner for prosthesis that is used by dentists (Emag EM070), and a provision to keep the screen separated from the bath's walls. This will cost more than a new screen, but it is also usable for other purposes.
p.s. The intended use of the ultrasonic bath is not for reversing the damage from IPA but for example when the screen it is polluted with a sticky seal during replacement, or a fingerprint.