Cleaning a Pentax Spotmatic mirror box back in 2003 vs now

Back when I started out in 2003 at a shop in Portland, I'd use a Q-tip with lighter fluid to clean mirror boxes on Pentax Spotmatics. Took forever and you had to be careful not to leave lint. Now I use a Sensor Scope with a microfiber swab and get it done in about 2 minutes flat. Any of you still using the old Q-tip method or did you switch over too?

4 comments

4 Comments

alicecraig1mo ago

Oh please, lighter fluid is fine if you're not a klutz.

jakewhite1mo ago

Lighter fluid is risky on old mirror boxes because it can seep past the foam seals and mess up the focusing screen or even the prism coating. Those Spotmatic seals are probably dried out by now anyway. I quit using it back in 2005 after watching a guy ruin a pristine SMC Takumar by getting lighter fluid behind the mirror. The Sensor Scope method works great but you still need to be careful with those old mirrors - they can get scratched if you press too hard. For really stubborn haze I just use a dry microfiber swab and gentle pressure. Never had any luck with Q-tips leaving lint behind in the corners.

emery2901mo ago

You ever actually had lighter fluid mess up a prism coating yourself, or are we just passing around stories? I've cleaned a dozen old Spotmatic and K1000 bodies with Ronsonal and never had a problem, even with crusty foam seals. The trick is using a tiny amount on a swab and dabbing, not soaking it. A guy on the Pentax Forums soaked his whole mirror box with a syringe and it ruined his focus screen, sure, but that's operator error not the fluid. Q-tips are fine too if you don't have arthritic hands and can control the pressure. I've pulled gunk off mirrors that microfiber just pushed around, and lighter fluid cut it in one pass. Your mileage varies I guess, but I'd rather risk a careful rinse than leave haze eating away at coatings for another decade.

james_bell27d ago

Yeah but that's not quite right about the dry microfiber swab thing. Those old Pentax mirrors have a front surface coating that's way softer than people think, and dry swabbing them is exactly how you get micro scratches that show up as weird streaks in the viewfinder later. I've seen more mirrors messed up by people trying to be gentle with dry swabs than by lighter fluid done right. The real trick nobody talks about is that you gotta use a tiny bit of moisture to pick up the grit instead of pushing it around. Lighter fluid works because it dissolves the gunk rather than scraping it off. But honestly if your foam seals are that crusty you're better off just replacing them before you touch the mirror at all, saves yourself a headache.