Cleaning technique for LF lens element

js98367 · May 13, 2016

Situation: I picked up a 300mm Geronar f/9 for a very good price. When I got it home I noticed some dried small droplets on the inside of the rear element. Being a Cooke triplet derivative, the rear element is a single piece of glass attached to a funnel-shaped metal assembly. It seems a previous owner decided to blow out some dust and ended up haplessly adding spittle droplets to the multi-coating.

Technique question: Trying to clean the inside of the rear element is like trying to clean out the inside of a laboratory beaker. My finger with microfiber or lens tissue cannot reach the narrow affected areas. I do not want to damage the multi-coating of the rear element or get too much cleaning fluid into the rear element mount, but I do want to effectively clean it because I have read that damage or other distractions to either side of the rear element can have the most negative impact on image quality. Also, what kind of lens cleaner/appropriate solvent should I use that will be effective yet have the least negative impact on the delicate coating? In searching I have found solvent suggestions ranging from lens cleaning fluid, to naphtha/lighter fluid to vodka!

John near Seattle

shutterfinger · May 13, 2016

One's breath is one of if not the most effective lens cleaning agent in existence. Find a stick with a smooth end that will reach the glass then use your breath and a clean microfiber lens cleaning cloth to clean the lens using a light touch.

Jim Jones · May 14, 2016

I still have some Kodak Lens Cleaning Fluid, and have also used lens cleaner (advertised to be good for all kinds of lenses) from my optician. Maybe even Walmart still has lens cleaning kits.

tedr1 · May 14, 2016

There are several suitable cleaning agents, one of the most readily available is iso-propyl alcohol, it is safe for use on coatings and glass and metal and plastic. It can be purchased in small bottles at the pharmacy and many supermarkets, chose the concentrated form, 91% or 99% strength. There are special containers for dispensing lens cleaning solution that are inexpensive, they have a dish on top with stem that reaches down into the bottle and a simple pump piston mechanism that brings up a little at a time. This keeps the bulk of the solution out of contact with the atmosphere. The 99% IPA absorbs moisture from the atmosphere and dilutes itself when exposed to air. This can result in the solution leaving a trail of small water droplets on the glass, which doesn't happen with fresh 99% solution. My preferred method is to use sachets that contain one small tissue saturated in 99% IPA, they are one-use items and they are always pure. McMaster-Carr sells them, among many places, under the brand name Leader, get the variety without silicone, they are cheap, about $10 for 100.

js98367 · May 14, 2016

I am diabetic, a human pincushion, and I regularly use isopropyl alcohol pads in foil packets to clean the target skin area. I would be concerned about the level of abrasiveness of the saturated pad material. I do have plenty of microfiber that I could cut to fit a safe and controllable stick that could get to the far reaches of the element edge. I could wet the microfiber patch I cut with the alcohol patch and get to work. Thanks.

Jim Noel · May 14, 2016

I never use any liquid on a lens, nor do I ever use lens tissue, otherwise known as "lens sandpaper".
Go to a health food store ad get some activated charcoal capsules. Open several up and dump them in a 35mm canister, or similar. Using a top quality Q-tip,dip the end in the powder, knock off the excess and then in a circular motion, gently wipe the surface of the lens. No harm to the coating, no liquid to get between the cells, just a sparkling clean lens results.

Doingthebobs · May 14, 2016

I would always use a blower first, to gently get any dust out the way. Dust particles could be made of abrasive stuff and wiping will then scratch! Next I would use a lens brush as the bristles are far less likely to rub any particles into the surface than rubbing with a cloth. The bristles can also move any bits that are a bit sticky and get into the corners/edges. Only them would I use a clean microfiber cloth dry or wet, changing to a fresh contact surface constantly.

The other thing to remember is to make sure that any fluid used has completely dried off before reassembling. Fungus loves moisture and a damp atmosphere is where it breeds, like inside a assembled lens.

js98367 · May 15, 2016

I used a q-tip with a patch of microfiber cloth tied to the end with thread. I tapped it on an alcohol pad to lightly moisten it then gently went to work. The lens element cleaned up perfectly and the MC looks pristine. Thanks for everyone's help.
The activated charcoal as a mild abrasive sounds intriguing. An old photographer back in 1969 once mentioned the same cleaning technique using cigarette ash. I am going to try it on an older 35mm lens to experiment and develop my technique.

tedr1 · May 15, 2016

I described sachets of tissue with alcohol purpose designed for lens cleaning not medical use.

js98367 · May 15, 2016

tedr1 said:
I described sachets of tissue with alcohol purpose designed for lens cleaning not medical use.

Never seen those in a photo shop yet.

tedr1 · May 15, 2016

http://www.mcmaster.com/#lens-cleaners/=12fbldl

Cleaning technique for LF lens element

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