PSA: I cleaned a Pentax lens with rubbing alcohol and the coating came off

Had a Pentax-M 50mm f1.7 come in last week. Front element had some stubborn haze. I usually use lens cleaner, but I was out. Figured 70% isopropyl would be fine for a quick wipe. Big mistake. The coating started to haze up and smear immediately. It looked like a foggy mess. I stopped right away, but the damage was done. Now the element needs a full recoating job. I always thought alcohol was safe for glass. Learned it can wreck certain older coatings. Has anyone else run into this with vintage Pentax glass? What's your go-to for tough haze now?

3 comments

3 Comments

kim73320d ago

Honestly I've used 70% isopropyl on a bunch of old lenses with no issues, including a few Pentax ones. That haze you saw might have been the old coating breaking down already, and the alcohol just moved the gunk around. Sometimes haze is actually fungus etching or separation, and no cleaner will fix that. I still use a drop of alcohol on a microfiber for light cleaning, just not on super old or already damaged glass.

rowanellis20d ago

Disagree pretty strongly here. I've seen alcohol strip the coating right off a lens, it left a permanent cloudy patch. That stuff can be way too harsh, especially on vintage coatings that are already delicate. I stick to lens cleaner made for cameras, it's just not worth the risk.

clairem4712d ago

Avoid alcohol on anything older than the 80s, the coatings just can't handle it. I use a drop of distilled water with a tiny bit of dish soap for haze now, works way safer. Ruined a nice Takumar that way and never went back.