Clean an old lens?

[Hugo Zhang]

I have just received a very old brass lens of 7" long and 4 1/2" wide. There is a waterstop slot in the middle. In its long sleep, dust has coated the inside surfaces of the front and rear elements. I can't get either of them off the barrel to clean them. I have tried dust-off compressed air and vacuum cleaner. Some of the dust came off and there is still a thin yellow fine coating of dust there. My 14 year old son suggested that I soak the lens in distilled water.

Before I do something foolish to ruin this lens, I haved decided to ask help here.

Any experiences or ideas? Thanks.

[Paul Fitzgerald]

Hugo,

You could try 'painting' around the seam between the cells and barrel with acetone and let it soak in. Quite often the older lenses had the cells 'painted' shut, their version of Lock-Tite.

I would not recommend soaking it in water until after you get the cell free, you'll never get them dry, water spots and rust.

good luck with it.

[Glenn Thoreson]

What ever you do, DON'T soak the lens, or cells, in anything. Almost surely, there are cemented elements. If any liquid gets into the lens, it will seep into the balsam and can eventually, maybe immediately, render the whole thing useless. Many of these old lenses were ruined just by improperly squirting cleaning fluid onto the glass, rather than applying it to the cloth or tissue. There is surely a way to get it apart for proper cleaning. Without having to call in Mr Pipe Wrench.

[Jim Galli]

I have two pieces of old black inner tube that I use to get extra GRIP. You can get about 10X the torque just doing that one trick. If I can't break things loose that way I usually step back and think hard before I wreck something. Assuming you do get things apart and assuming it is a Petzval type, the rear group should come apart easily. With due respect to Glenn's sound advice, I fill the kitchen sink with hot water and dish washing detergent and put the glass in. The cemented group and the singles. Then I go do something else for a good long while. After a couple of hours I gently wash the glass with a cotton wash cloth, rinse in warm water, and dry with a soft cotton towel. I haven't had detergent and water attack a cemented group.

If it's a petzval with independent glasses at the rear, do yourself a favor and draw a good sketch. Maybe it's because I'm 54, but I can't remember what was in front or in back after about 5 minutes.

[Struan Gray]

Just make sure the cells or elements are not burnished in. Sometimes a maker would leave a thin cylinder of metal in the mount, which was then folded down over the glass to form a seal. I have a couple of older lenses where this has been done and there is no way to extract the glass without ruining the mount, and even then you are likely to chip an edge.

As Jim says, take notes, and if you have a digital camera, take disassembly photos too. Another trick is to mark the edges of the elements with a pencil so that you can put them back in the same relative alignment. You may find the pencil marks from the original assembly are still there, something I always find gives me the warm and fuzzies.

[Hugo Zhang]

Paul and Glenn,

I won't soak the the lens in water at this moment then. My original plan was to give it a quick soak in hot water with dish washing detergent and then rince in distilled water off and then dry the inside up using a hair dryer through the waterstop slot.

Jim,

It's the lens you have, a Voigtlander Euryscop IV. No.6. I couldn't even get the flange off the barrel after appling MD-40. You know how the lens look, without the flange off, there is no way I can even grip the rim of the rear cell.

All I want to do is to get the dust off the inside. Is there a powerful vacuum with a thin tube I can insert through the slot?

Struan,

I am afraid the cells are burnished in. I don't know. Jim has the same lens and I will listen to what he has to say.

Thanks, everyone!

[Paul Fitzgerald]

Hugo,

It's like a puppy, scared of the new house. Let it sit for a week to adjust.

Jim's advice about the rubber pads works very well. You can also put the pad on the workbench and press the lens into it to get maximum leverage.

Try a hair dryer to warm it up and dry out the rust between the threads. warm it up several times to let the steam vent out.

VERY LAST RESORT:
rust is crystals. You can tap around the rim of the barrel or the flange with a small wooden seafood mallet to jar the rust apart. Try warming it up first.

take your time, it did.